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Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin
Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
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Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin Hsin-Yun Sun a, Hsiao-Wei Liao b, Meng-Huei Sheng c, Hui-Min Tai a, Ching-Hua Kuo b,d, Wang-Huei Sheng a,⁎ a
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan Jia-Nan University of Pharmacy and Science, Tainan, Taiwan d Department of Pharmacy, National Taiwan University Hospital, Taipei, Taiwan b c
a r t i c l e
i n f o
Article history: Received 30 January 2016 Received in revised form 18 March 2016 Accepted 23 April 2016 Available online xxxx Keywords: Generic Brand-name Levofloxacin Bioequivalence
a b s t r a c t Generic agents play a crucial role in reducing the cost of medical care in many countries. However, the therapeutic equivalence remains a great concern. Our study aims to assess the in vitro antimicrobial activity and bioequivalence between generic and brand-name levofloxacin. Enantiomeric purity test, dissolution test, and in vitro antimicrobial susceptibility against seven clinically important pathogens by the agar dilution method were employed to assess the similarity between four generic products and brand-name levofloxacin (Daiichi Sankyo). All the generic and brand-name levofloxacin passed enantiomeric purity test. The results of dissolution tests were not similar among the generic products and the brand-name levofloxacin. Compared with the generic products, the brand-name levofloxacin had the smallest mean variations (−25% to 13%) with reference standard (United States Pharmacopeia levofloxacin Reference Standards). Variations were observed particularly in dissolution profiles and in vitro activity between generic products and brand-name levofloxacin. © 2016 Elsevier Inc. All rights reserved.
1. Introduction World Health Organization (WHO) and drug regulatory agencies support the use of generic medicines since they reduce spending on prescription drugs significantly (Generic Pharmaceutical Association, 2012; World Health Organization, 1998). It is estimated that generic products save 1.07 trillion US dollars in the US healthcare system from 2002 to 2011(Generic Pharmaceutical Association, 2012), and offer irreplaceable therapeutic options in countries lacking or not having affordable access to the brand-name products (World Health Organization, 1998). For the United States Food and Drug Administration (FDA), it is required for a generic product to demonstrate that its product is bioequivalent to the corresponding brand-name product “Drug Price Competition and Patent Term Restoration Act of 1984, 1984. Public Law 98–417, 98 Stat. 1585–1605,” 1984). Bioequivalence means that the generic drug and the reference drug will reach the systemic circulation at an equivalent relative rate and extent (Davit et al., 2009). WHO defines two products as therapeutically equivalent if they are pharmaceutically equivalent and their effects with respect to both efficacy and safety are essentially the same without direct proof (World Health Organization, 1998), and Taiwan followed the same regulations (Taiwan Generic Pharmaceutical Association, 2010).
⁎ Corresponding author. Tel.: +886-2-23123456x63885; fax: +886-2-23971412. E-mail address: [email protected] (W.-H. Sheng).
However, generic substitution continues to be a debate among healthcare professionals, members of the pharmaceutical industry, consumers, and government officials. Concern regarding its efficacy remains, especially when a breakthrough seizure or increased seizure frequency was reported after switching to a generic without other provoking factors in some patients, who were well controlled on a brand antiepileptic drugs (Berg et al., 2008), or observation of increased warfarin doses and decreased international normalized ratio response was reported (Halkin et al., 2003). Several systematic review and metaanalysis were performed to evaluate clinical equivalence of generic and brand-name drugs used in cardiovascular disease (Kesselheim et al., 2008), seizure control (Kesselheim et al., 2010; Yamada and Welty, 2011), and the use of generic warfarin (Dentali et al., 2011). These studies concluded that brand-name products used in cardiovascular disease are not superior to generic products (Kesselheim et al., 2008), that there was no association between loss of seizure control and generic substitution (Kesselheim et al., 2010; Yamada and Welty, 2011), and that generic warfarin products may be as safe and effective as brand name products (Dentali et al., 2011). Nevertheless, closer monitoring was suggested when switching brands, as variations in individual response may be seen (Dentali et al., 2011; Kesselheim et al., 2010). Several studies compare the generic and brand-name antimicrobial agents, such as meropenem (Agudelo et al., 2014; Fujimura and Watanabe, 2012), vancomycin (Hadwiger et al., 2012; Nambiar et al., 2012; Tattevin et al., 2013; Vesga et al., 2010), teicoplanin (Fujimura and Watanabe, 2012), ciprofloxacin (Rodriguez et al., 2015), oxacillin
http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015 0732-8893/© 2016 Elsevier Inc. All rights reserved.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
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H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
Table 1 Results of enantiomeric purity test of levofloxacin produced by brand-name (Daiichi Sankyo) and 3 generic manufacturers. All the generic and brand-name drugs showed no more than 1.0% of D-ofloxacin. Products
D-ofloxacin/levofloxacin (%) (mean ± STD)
Results
Brand-name Generic A Generic B Generic C
0.251±0.019 0.366±0.020 0.123±0.004 0.233±0.026
Pass Pass Pass Pass
(Rodriguez et al., 2010), gentamicin (Zuluaga et al., 2010), and amoxicillin (Del Tacca et al., 2009; Kassaye and Genete, 2013). Of these studies, some showed no significant differences (Hadwiger et al., 2012; Nambiar et al., 2012; Rodriguez et al., 2015; Tattevin et al., 2013) while the others demonstrated differences (Del Tacca et al., 2009; Fujimura and Watanabe, 2012; Kassaye and Genete, 2013; Mastoraki et al., 2008; Rodriguez et al., 2010; Vesga et al., 2010; Zuluaga et al., 2010). The National Health Insurances (NHI) program in Taiwan, launched in 1995, has successfully provided universal and quality healthcare to the people at affordable costs (Bureau of National Health Insurance, DoH, Executive Yuan, 2012). To make the cost of medicines affordable in the long run, use of generic drugs is an attractive way for disinvestment (Hughes and Ferner, 2010). Generic products account for 63% of all US prescriptions for drugs in 2007 (Frank, 2007), and 83% in the community in England in 2008 (Duerden and Hughes, 2010). Levofloxacin is a fluoroquinolone antimicrobial agent with excellent antimicrobial activity against many clinically significant pathogens, such as Pseudomonas aeruginosa, Escherichia coli, and Streptococcus pneumoniae, etc. Levofloxacin has both oral and parental formulations with good bioavailability. This is convenient for physicians to use it in both inpatient and outpatient settings. Therefore, generic products for levofloxacin are used worldwide. The present study aimed to evaluate the similarity between generic and brand-name levofloxacin in Taiwan by enantiomeric purity test, dissolution test, and in vitro activity against clinically significant pathogens by the agar dilution method. 2. Materials and methods 2.1. Manufacturers of antimicrobial agents
The USP Ofloxacin RS and USP Levofloxacin RS standards were prepared separately in methanol at a concentration of 1000 μg mL −1 as stock solution. And the 100 μg mL −1 working solution was prepared by diluting the stock solution with the DI water. To test the enantiomeric purity of the levofloxacin tablet, 20 mg levofloxacin tablet powder was dissolved in the DI water to obtain the 80 μg mL −1 test solution. The enantiomeric purity of Levofloxacin was calculated using Eq. (1): Enantiomeric purity ¼ ðrU = rT Þ 100 rU ¼ peak response for D−ofloxacin rT ¼ sum of responses of all peaks
ð1Þ
2.3. Dissolution test The dissolution test followed the protocol used by Maezawa et al.(Maezawa et al., 2013; The Ministry of Health, LaW, 2006) The procedures are briefly described as follows: first, place one levofloxacin tablet in the paddle and dissolve in 900 mL 34.2 mM NaCl (pH 1.2, adjusted with HCl); second, set the paddle rotation rate at 50 rpm at 37 ± 0.5 °C; third, collect the solution at 5, 10, 15, 20, 30, 45, and 60 min after starting the dissolution procedure; fourth, determine the concentration of levofloxacin in the solution by high performance liquid chromatography. The dissolution curves generated from the generic tablets were compared with the dissolution curve of brand name tablet. The f2 values were used to indicate the similarity of dissolution curves between generic and brand name tablets. The f2 values were obtained from following equation: 100 f 2 ¼ 50 log sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi n 1X 2 1þ ðR −T t Þ n t¼1 t f2: Predict bioequivalence from dissolution and examines waivers for BE studies In this equation, f2 was the similarity factor, n was the number of time points, Rt was the mean percent drug dissolved of a reference product, and Tt was the mean percent drug dissolved of a test product. The dissolution curve of tested tablet was similar to the brand name tablet when the f2 value was large than 50.
The manufacturer of the brand-name levofloxacin was Daiichi Sankyo Company in Japan. Four manufacturers of generic levofloxacin were selected for the present study, and their products were designated as Generic A, B, C, and D. The generic levofloxacin included 3 parenteral (Generic A, B, C) and 3 oral (Generic A, B, D) formulations. US Pharmacopeia (USP) Ofloxacin Reference Standards (RS) and USP Levofloxacin RS were used for Enantiomeric purity test and in vitro activity as reference. 2.2. Enantiomeric purity test An enantiomer is one of two stereoisomers that are mirror images of each other that are not identical. D-ofloxacin and levofloxacin were enantiomer for each other. We used enantiomeric purity test to make sure that levofloxacin was the main component of the brand-name and genetic versions of levofloxacin. The HPLC system consisted of an L-2130 HTA solvent delivery pump, a L-2200 autosampler, a UV1000 wavelength detector programmable UV detector wave-length 245 nm and the computing integrator for HPLC D-2000Elite on Windows (version 1.2, Hitachi High TechnologiesCorporation, Tokyo, Japan). A Phenomenex® Luna 5 μm C18 (2) 250*4.60 mm column was applied for separation. The mobile phase was composed of 8 mM D-phenylalanine and 3 mM copper sulfate pentahydrate in DI water (solvent A) and ACN (solvent B). A 15% isocratic solvent B was performed for the analysis, and the flow rate was set at 1.0 mL per minute.
Fig. 1. Dissolution curves of oral Generic A, B, D and brand-name levofloxacin in the 34.2 mM NaCl at pH1.2. The dissolution curves of Generic A and B were not considered to be similar to that of the brand-name tablet.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx Table 2 The dissolution profiles of oral brand-name levofloxacin (Daiichi Sankyo) and generic levofloxacin products in the 34.2 mM NaCl at pH1.2. The dissolution curve of generic drug was considered to be similar to the brand name tablet when the f2 value was larger than 50. Manufacturers
Brand-name Generic A Generic B Generic D
3
The concentrations of antimicrobial agents that were tested against all bacteria ranged from 0.06 to 128 mg/L. 3. Results
Dissolution profile
% dissolved at 30 minutes
3.1. Enantiomeric purity test
f2 value
Similarity
%
Pass/Fail
Reference 24 32 NA
Reference No No NA
100.75 89.32 104.03 94.04
Pass Pass Pass Pass
A total of 3 parenteral generic formulations (Generic A, B, C) and brand-name levofloxacin (Daiichi Sankyo) were analyzed for enantiomeric purity test. All the generic and brand-name drugs showed no more than 1.0% of D-ofloxacin (Table 1). 3.2. Dissolution test
2.4. Bacterial isolates Totally 20 clinical isolates of each of P. aeruginosa, Acinetobacter baumannii, Burkholderia cepacia complex, Stenotrophomonas maltophilia, E. coli, Klebsiella pneumoniae, and Staphylococcus aureus isolates, collected randomly at the National Taiwan University Hospital (NTUH) were studied. Bacterial isolates were mostly isolated from the blood and were collected from both outpatients and inpatients in different wards. Isolates were stored in Mueller–Hinton broth with 15% glycerol and frozen at −80 °C. Extended-spectrum beta-lactamase (ESBL)-production of the bacteria was detected by the recommended phenotypic confirmatory test (Clinical and Laboratory Standards Institute, 2016).
2.5. Susceptibility testing The minimal inhibitory concentrations (MICs) of each antimicrobial agent for the tested bacterial isolates were determined once by the agar dilution method according to the Clinical Laboratory Standards Institute (CLSI). (Clinical and Laboratory Standards Institute, 2016) All MIC tests were repeated. If discrepancies of results occurred between the 2 tests, a third test was performed. For each isolate, variation was calculated by one minus the ratio of MIC of levofloxacin from each company (MICc) divided by the MIC (MICs) of USP Levofloxacin RS [1-(MICc/MICs)]. (Jones et al., 2008) Mean variation was calculated by the sum of variations for the same organism divided by the number of the same organism.(Jones et al., 2008) With the use of a Steers replicator, 10 4 colony-forming units (CFU) of bacteria were inoculated onto Mueller– Hinton agar plates containing a series 2-fold dilution of antimicrobial agents. Following inoculation, the agar plates were incubated at 35 °C in 5% CO2 for 18–20 h. The MIC was defined as the lowest concentration of antimicrobial agent that completely inhibited the growth of bacteria.
The dissolution test was performed for 3 oral generic formulations (Generic A, B, D) and brand-name levofloxacin (Daiichi Sankyo) in acid buffer (pH = 1.2) (Fig. 1). The f2 values, the indicator of the similarity of dissolution curves between generic and brand-name tablets, were shown in Table 2. Generic A and B had different dissolution results in acid solutions with that from brand-name levofloxacin (Table 2). 3.3. Susceptibility testing The MIC ranges and mean variations of the 3 parenteral generic formulations (Generic A, B, C) and brand-name levofloxacin (Daiichi Sankyo) compared with USP levofloxacin RS are presented in Tables 3, 4 and Fig. 2. Compared with the 3 generic levofloxacin, the brandname levofloxacin had similar MIC ranges as USP levofloxacin RS did and had the smallest mean variations (−25% to +13%) compared with USP levofloxacin RS. The mean variations of the 3 generic levofloxacin were 0% to −50%, −160% to +25%, and −50% to +19%, respectively (Table 4 and Fig. 2). 4. Discussion We demonstrated that the purity of the 3 generic levofloxacin were similar with that of brand-name levofloxacin. However, variations in dissolution curves and in vitro antimicrobial activity against clinically significant pathogens were observed. Different additives in generic drugs despite the same ingredients as those of the brand-name drug might explain our findings (Agudelo et al., 2014). Differences in in vitro antimicrobial activity between generic and brand-name drugs have also been reported in other studies (Fujimura and Watanabe, 2012; Jones et al., 2008). A study showed a decrement of average 16% activity for 23 tested piperacillin/tazobactam generic lots compared with brand-name product (Jones et al., 2008). Another study also demonstrated that the potency of the generic products of vancomycin and
Table 3 Minimal inhibitory concentration (MIC) ranges of brand-name (Daiichi Sankyo) and 3 generic parenteral levofloxacin compared with that of USP levofloxacin RS. Organism
No. of isolates
Reference standard
Brand-name levofloxacin
Generic A
Generic B
Generic C
Pseudomonas aeruginosa Resistant Pseudomonas aeruginosa Acinetobacter baumannii MDR Acinetobacter baumannii Stenotrophomonas maltophilia Resistant Stenotrophomonas maltophilia Burkholderia cepacia complex Resistant Burkholderia cepacia complex Escherichia coli ESBL Escherichia coli Klebsiella pneumoniae ESBL Klebsiella pneumoniae Staphylococcus aureus Staphylococcus aureus (MRSA)
16 4 10 10 16 4 18 2 14 6 16 4 11 9
0.125–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.25 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.25 8–64
0.125–2 32–128 0.06–0.5 8–64 1–2 4–6 1–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.25–0.5 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.5 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.25 8–64
Abbreviations: ESBL, Extended-spectrum beta-lactamase; MDR, multi-drug resistant; ESBL, MIC, minimal inhibitory concentration; MRSA, methicillin-resistant Staphylococcus aureus; NA, not applicable; No., number; RS, reference standard; USP Pharmacopeia.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
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H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
Table 4 Mean MIC variations of brand-name (Daiichi Sankyo) and 3 generic parenteral levofloxacin compared with that of USP levofloxacin RS. Definitions: For each isolate, variation was calculated by one minus the ratio of MIC of levofloxacin from each company (MICg) divided by the MIC (MICu) of USP Levofloxacin RS [1 − (MICg/MIGu)]. Mean variation was calculated by the sum of variations for the same organism divided by the number of the same organism. Organism
No. of isolates
Brand-name levofloxacin
Generic A
Generic B
Generic C
Pseudomonas aeruginosa Resistant Pseudomonas aeruginosa Acinetobacter baumannii MDR Acinetobacter baumannii Stenotrophomonas maltophilia Resistant Stenotrophomonas maltophilia Burkholderia cepacia complex Resistant Burkholderia cepacia complex Escherichia coli ESBL Escherichia coli Klebsiella pneumoniae ESBL Klebsiella pneumoniae Staphylococcus aureus Staphylococcus aureus (MRSA)
16 4 10 10 16 4 18 2 14 6 16 4 11 9
13% 0% −10% 0% −6% 0% 0% 0% −7% 0% 6% −25% 0% 0%
0% 0% −50% −10% −25% 0% −17% 0% −7% 0% −31% −25% −18% −11%
25% 0% −30% −160% −50% 0% 0% 0% −29% 0% 0% −25% −9% −22%
19% 0% −40% −30% −50% 0% −6% 0% −21% 0% 0% −25% −9% 0%
Abbreviations: ESBL, Extended-spectrum beta-lactamase; MDR, multi-drug resistant; ESBL, MIC, minimal inhibitory concentration; MRSA, methicillin-resistant Staphylococcus aureus; NA, not applicable; No., number; RS, reference standard; USP Pharmacopeia.
Hatch-Waxman Act Drug Price Competition and Patent Term Restoration Act of 1984, 1984. Public Law 98–417, 98 Stat. 1585–1605," 1984; Frank, 2007). This Act obviated the necessity of conducting clinical trials for generic manufacturers to show the same safety and efficacy tests as brand-name manufacturers, but required bioequivalence to the active ingredients of the original brand-name drugs (Frank, 2007). Drug peak plasma concentration and area under the plasma drug concentration versus time curve, presenting drug rate and extent of absorption, respectively, are bioequivalence measures (Davit et al., 2009). Dissolution testing (The Ministry of Health, LaW, 2006) and highperformance liquid chromatography assay for purity (Nambiar et al., 2012) are also used to compare generic and brand-name drugs by some authorities. The US FDA reviewed 12 years of bioequivalence data, including 2070 single-dose clinical bioequivalence studies of orally administered generic drug products from 1996 through 2007, and concluded that the generic drug formulations are therapeutically equivalent to their brand-name counterparts (Davit et al., 2009). Nevertheless, another study in Japan noted different dissolution profiles between generic and brand-name drugs (Maezawa et al., 2013). In addition to the bioequivalence studies, numerous methods have been employed to assess whether generic antibiotics performed well
teicoplainin is lower than that of the branded drugs by 14.6% and 17.3%, respectively (Fujimura and Watanabe, 2012). Thus, hospital formularies should be cautious when applying generic products. Worldwide use of generic drugs has become a trend because generic drugs can significantly decrease drug expenses in national medical expenditures (Generic Pharmaceutical Association, 2012; Hughes and Ferner, 2010). In UK, the rate of generic prescribing has risen from 35% in the community in the mid-1900s to 83% in 2008 (NHS Information Centre, PSU, 2009). Furthermore, the Health (Pricing and Supply of Medical Goods) Act 2013 commenced on the Jun 24, 2013 was legislated to establish a list of groups of interchangeable medicinal products which may be substituted for each other in order to enable savings to be made for patients or the Health Service Executive, or both (Department of Health, 2013), and annual savings of 72 million pounds are expected after the implement of this act (Hughes and Ferner, 2010). Likewise, generic drugs account for only 18.6% in 1984, but 63% of all US prescriptions for drugs in 2007 (Frank, 2007), and have saved the US health care system approximately 1.07 trillion from 2002 through 2011 with 192.8 billion in savings achieved in 2011 (Generic Pharmaceutical Association, 2012). Such changes could be attributed to the Drug Price Competition and Patent Restoration Act of 1984, or the
-0.64% -1.11% -0.82% -0.04%
total -40% -40%
Variation All S. maltophilia
-20%
-5%
Variation All B. cepacia
-15%
Variation All KP
0%
0% -15% -15%
-5% 0%
Variation All P. aeruginosa
0% -15% -20%
Variation All E. coli Variation All AB
0%
-5% -5%
-30%
Variation All S. aureus
-95%
-100%
Generic C Generic B Generic A Brand-name
-5%
15% 20% 10%
-5% -5%
-35% -30%
-80%
-60%
-40%
-5%
-20%
0%
20%
Fig. 2. Mean variations of brand-name and 3 generic levofloxacin compared with that of USP levofloxacin RS for test bacterial isolates. MIC, minimal inhibitory concentration; AB, Acinetobacter baumannii; KP, Klebsiella pneumoniae, reference standard; USP, US Pharmacopeia.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
as the brand-name ones, such as in vitro antibacterial potency against the target bacteria by MIC (Fujimura and Watanabe, 2012; Jones et al., 2008), in vivo efficacy by bactericidal efficacy (Vesga et al., 2010), the neutropenic mouse infection model (Rodriguez et al., 2010; Zuluaga et al., 2010), neutropenic guinea pig infection model (Agudelo et al., 2014) and rabbit endocarditis model (Tattevin et al., 2013). Some results demonstrated that bioequivalence of generic products of antibiotics do not guarantee therapeutic equivalence evaluated by neutropenic animal models (Agudelo et al., 2014; Rodriguez et al., 2010; Vesga et al., 2010; Zuluaga et al., 2010), but some did not (Rodriguez et al., 2015; Tattevin et al., 2013). Thus, therapeutic equivalence could not be reliably predicted from pharmaceutical equivalence of generic products. Judicious use of generic antibiotics is recommended given the benefit of reduced cost and the drawback of possible therapeutic nonequivalence. There are some limitations in our study to be acknowledged. First, we only tested generic levofloxacin by 3 manufacturers in Taiwan. However, given being the top 3 in the market, it is reasonable to test generic levofloxacin produced by these 3 manufacturers. Second, we employed only enantiomeric purity test, dissolution test, and in vitro activity against clinically significant pathogens to assess the similarity between generic and brand-name levofloxacin, but not animal models or post-marketing clinical study on healthy volunteers. Because differences in in vitro activity have existed, it is possible that differences in in vivo activity also existed. Further comparisons in animal models and prospective clinical studies are warranted. Lastly, we did not measure additives in both generic and brand-name drugs which might explain our findings. In summary, we have shown the differences in in vitro antimicrobial activity against clinically significant pathogens and dissolution test between generic and brand-name levofloxacin. Periodic monitoring of manufacture lots and therapeutic response of patients treated with generic levofloxacin are suggested. Acknowledgement This work was funded by Daiichi Sankyo, Inc.. The funder had no role in study design, data collection and interpretation, or the decision to submit the work for publication. References Agudelo M, Rodriguez CA, Pelaez CA, Vesga O. Even apparently insignificant chemical deviations among bioequivalent generic antibiotics can lead to therapeutic nonequivalence: the case of meropenem. Antimicrob Agents Chemother 2014;58:1005–18. Berg MJ, Gross RA, Tomaszewski KJ, Zingaro WM, Haskins LS. Generic substitution in the treatment of epilepsy: case evidence of breakthrough seizures. Neurology 2008;71: 525–30. Bureau of National Health Insurance, DoH, Executive Yuan. Universal Health Coverage in Taiwa; 2012. Clinical and Laboratory Standards Institute. Clinical and Laboratory Standards Institute (CLSI) Performance standards for antimicrobial susceptibility testing. 26th informational supplement; 2016. Davit BM, Nwakama PE, Buehler GJ, Conner DP, Haidar SH, Patel DT, et al. Comparing generic and innovator drugs: a review of 12 years of bioequivalence data from the United States Food and Drug Administration. Ann Pharmacother 2009;43:1583–97.
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Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
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Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin Hsin-Yun Sun a, Hsiao-Wei Liao b, Meng-Huei Sheng c, Hui-Min Tai a, Ching-Hua Kuo b,d, Wang-Huei Sheng a,⁎ a
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan Jia-Nan University of Pharmacy and Science, Tainan, Taiwan d Department of Pharmacy, National Taiwan University Hospital, Taipei, Taiwan b c
a r t i c l e
i n f o
Article history: Received 30 January 2016 Received in revised form 18 March 2016 Accepted 23 April 2016 Available online xxxx Keywords: Generic Brand-name Levofloxacin Bioequivalence
a b s t r a c t Generic agents play a crucial role in reducing the cost of medical care in many countries. However, the therapeutic equivalence remains a great concern. Our study aims to assess the in vitro antimicrobial activity and bioequivalence between generic and brand-name levofloxacin. Enantiomeric purity test, dissolution test, and in vitro antimicrobial susceptibility against seven clinically important pathogens by the agar dilution method were employed to assess the similarity between four generic products and brand-name levofloxacin (Daiichi Sankyo). All the generic and brand-name levofloxacin passed enantiomeric purity test. The results of dissolution tests were not similar among the generic products and the brand-name levofloxacin. Compared with the generic products, the brand-name levofloxacin had the smallest mean variations (−25% to 13%) with reference standard (United States Pharmacopeia levofloxacin Reference Standards). Variations were observed particularly in dissolution profiles and in vitro activity between generic products and brand-name levofloxacin. © 2016 Elsevier Inc. All rights reserved.
1. Introduction World Health Organization (WHO) and drug regulatory agencies support the use of generic medicines since they reduce spending on prescription drugs significantly (Generic Pharmaceutical Association, 2012; World Health Organization, 1998). It is estimated that generic products save 1.07 trillion US dollars in the US healthcare system from 2002 to 2011(Generic Pharmaceutical Association, 2012), and offer irreplaceable therapeutic options in countries lacking or not having affordable access to the brand-name products (World Health Organization, 1998). For the United States Food and Drug Administration (FDA), it is required for a generic product to demonstrate that its product is bioequivalent to the corresponding brand-name product “Drug Price Competition and Patent Term Restoration Act of 1984, 1984. Public Law 98–417, 98 Stat. 1585–1605,” 1984). Bioequivalence means that the generic drug and the reference drug will reach the systemic circulation at an equivalent relative rate and extent (Davit et al., 2009). WHO defines two products as therapeutically equivalent if they are pharmaceutically equivalent and their effects with respect to both efficacy and safety are essentially the same without direct proof (World Health Organization, 1998), and Taiwan followed the same regulations (Taiwan Generic Pharmaceutical Association, 2010).
⁎ Corresponding author. Tel.: +886-2-23123456x63885; fax: +886-2-23971412. E-mail address: [email protected] (W.-H. Sheng).
However, generic substitution continues to be a debate among healthcare professionals, members of the pharmaceutical industry, consumers, and government officials. Concern regarding its efficacy remains, especially when a breakthrough seizure or increased seizure frequency was reported after switching to a generic without other provoking factors in some patients, who were well controlled on a brand antiepileptic drugs (Berg et al., 2008), or observation of increased warfarin doses and decreased international normalized ratio response was reported (Halkin et al., 2003). Several systematic review and metaanalysis were performed to evaluate clinical equivalence of generic and brand-name drugs used in cardiovascular disease (Kesselheim et al., 2008), seizure control (Kesselheim et al., 2010; Yamada and Welty, 2011), and the use of generic warfarin (Dentali et al., 2011). These studies concluded that brand-name products used in cardiovascular disease are not superior to generic products (Kesselheim et al., 2008), that there was no association between loss of seizure control and generic substitution (Kesselheim et al., 2010; Yamada and Welty, 2011), and that generic warfarin products may be as safe and effective as brand name products (Dentali et al., 2011). Nevertheless, closer monitoring was suggested when switching brands, as variations in individual response may be seen (Dentali et al., 2011; Kesselheim et al., 2010). Several studies compare the generic and brand-name antimicrobial agents, such as meropenem (Agudelo et al., 2014; Fujimura and Watanabe, 2012), vancomycin (Hadwiger et al., 2012; Nambiar et al., 2012; Tattevin et al., 2013; Vesga et al., 2010), teicoplanin (Fujimura and Watanabe, 2012), ciprofloxacin (Rodriguez et al., 2015), oxacillin
http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015 0732-8893/© 2016 Elsevier Inc. All rights reserved.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
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H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
Table 1 Results of enantiomeric purity test of levofloxacin produced by brand-name (Daiichi Sankyo) and 3 generic manufacturers. All the generic and brand-name drugs showed no more than 1.0% of D-ofloxacin. Products
D-ofloxacin/levofloxacin (%) (mean ± STD)
Results
Brand-name Generic A Generic B Generic C
0.251±0.019 0.366±0.020 0.123±0.004 0.233±0.026
Pass Pass Pass Pass
(Rodriguez et al., 2010), gentamicin (Zuluaga et al., 2010), and amoxicillin (Del Tacca et al., 2009; Kassaye and Genete, 2013). Of these studies, some showed no significant differences (Hadwiger et al., 2012; Nambiar et al., 2012; Rodriguez et al., 2015; Tattevin et al., 2013) while the others demonstrated differences (Del Tacca et al., 2009; Fujimura and Watanabe, 2012; Kassaye and Genete, 2013; Mastoraki et al., 2008; Rodriguez et al., 2010; Vesga et al., 2010; Zuluaga et al., 2010). The National Health Insurances (NHI) program in Taiwan, launched in 1995, has successfully provided universal and quality healthcare to the people at affordable costs (Bureau of National Health Insurance, DoH, Executive Yuan, 2012). To make the cost of medicines affordable in the long run, use of generic drugs is an attractive way for disinvestment (Hughes and Ferner, 2010). Generic products account for 63% of all US prescriptions for drugs in 2007 (Frank, 2007), and 83% in the community in England in 2008 (Duerden and Hughes, 2010). Levofloxacin is a fluoroquinolone antimicrobial agent with excellent antimicrobial activity against many clinically significant pathogens, such as Pseudomonas aeruginosa, Escherichia coli, and Streptococcus pneumoniae, etc. Levofloxacin has both oral and parental formulations with good bioavailability. This is convenient for physicians to use it in both inpatient and outpatient settings. Therefore, generic products for levofloxacin are used worldwide. The present study aimed to evaluate the similarity between generic and brand-name levofloxacin in Taiwan by enantiomeric purity test, dissolution test, and in vitro activity against clinically significant pathogens by the agar dilution method. 2. Materials and methods 2.1. Manufacturers of antimicrobial agents
The USP Ofloxacin RS and USP Levofloxacin RS standards were prepared separately in methanol at a concentration of 1000 μg mL −1 as stock solution. And the 100 μg mL −1 working solution was prepared by diluting the stock solution with the DI water. To test the enantiomeric purity of the levofloxacin tablet, 20 mg levofloxacin tablet powder was dissolved in the DI water to obtain the 80 μg mL −1 test solution. The enantiomeric purity of Levofloxacin was calculated using Eq. (1): Enantiomeric purity ¼ ðrU = rT Þ 100 rU ¼ peak response for D−ofloxacin rT ¼ sum of responses of all peaks
ð1Þ
2.3. Dissolution test The dissolution test followed the protocol used by Maezawa et al.(Maezawa et al., 2013; The Ministry of Health, LaW, 2006) The procedures are briefly described as follows: first, place one levofloxacin tablet in the paddle and dissolve in 900 mL 34.2 mM NaCl (pH 1.2, adjusted with HCl); second, set the paddle rotation rate at 50 rpm at 37 ± 0.5 °C; third, collect the solution at 5, 10, 15, 20, 30, 45, and 60 min after starting the dissolution procedure; fourth, determine the concentration of levofloxacin in the solution by high performance liquid chromatography. The dissolution curves generated from the generic tablets were compared with the dissolution curve of brand name tablet. The f2 values were used to indicate the similarity of dissolution curves between generic and brand name tablets. The f2 values were obtained from following equation: 100 f 2 ¼ 50 log sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi n 1X 2 1þ ðR −T t Þ n t¼1 t f2: Predict bioequivalence from dissolution and examines waivers for BE studies In this equation, f2 was the similarity factor, n was the number of time points, Rt was the mean percent drug dissolved of a reference product, and Tt was the mean percent drug dissolved of a test product. The dissolution curve of tested tablet was similar to the brand name tablet when the f2 value was large than 50.
The manufacturer of the brand-name levofloxacin was Daiichi Sankyo Company in Japan. Four manufacturers of generic levofloxacin were selected for the present study, and their products were designated as Generic A, B, C, and D. The generic levofloxacin included 3 parenteral (Generic A, B, C) and 3 oral (Generic A, B, D) formulations. US Pharmacopeia (USP) Ofloxacin Reference Standards (RS) and USP Levofloxacin RS were used for Enantiomeric purity test and in vitro activity as reference. 2.2. Enantiomeric purity test An enantiomer is one of two stereoisomers that are mirror images of each other that are not identical. D-ofloxacin and levofloxacin were enantiomer for each other. We used enantiomeric purity test to make sure that levofloxacin was the main component of the brand-name and genetic versions of levofloxacin. The HPLC system consisted of an L-2130 HTA solvent delivery pump, a L-2200 autosampler, a UV1000 wavelength detector programmable UV detector wave-length 245 nm and the computing integrator for HPLC D-2000Elite on Windows (version 1.2, Hitachi High TechnologiesCorporation, Tokyo, Japan). A Phenomenex® Luna 5 μm C18 (2) 250*4.60 mm column was applied for separation. The mobile phase was composed of 8 mM D-phenylalanine and 3 mM copper sulfate pentahydrate in DI water (solvent A) and ACN (solvent B). A 15% isocratic solvent B was performed for the analysis, and the flow rate was set at 1.0 mL per minute.
Fig. 1. Dissolution curves of oral Generic A, B, D and brand-name levofloxacin in the 34.2 mM NaCl at pH1.2. The dissolution curves of Generic A and B were not considered to be similar to that of the brand-name tablet.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx Table 2 The dissolution profiles of oral brand-name levofloxacin (Daiichi Sankyo) and generic levofloxacin products in the 34.2 mM NaCl at pH1.2. The dissolution curve of generic drug was considered to be similar to the brand name tablet when the f2 value was larger than 50. Manufacturers
Brand-name Generic A Generic B Generic D
3
The concentrations of antimicrobial agents that were tested against all bacteria ranged from 0.06 to 128 mg/L. 3. Results
Dissolution profile
% dissolved at 30 minutes
3.1. Enantiomeric purity test
f2 value
Similarity
%
Pass/Fail
Reference 24 32 NA
Reference No No NA
100.75 89.32 104.03 94.04
Pass Pass Pass Pass
A total of 3 parenteral generic formulations (Generic A, B, C) and brand-name levofloxacin (Daiichi Sankyo) were analyzed for enantiomeric purity test. All the generic and brand-name drugs showed no more than 1.0% of D-ofloxacin (Table 1). 3.2. Dissolution test
2.4. Bacterial isolates Totally 20 clinical isolates of each of P. aeruginosa, Acinetobacter baumannii, Burkholderia cepacia complex, Stenotrophomonas maltophilia, E. coli, Klebsiella pneumoniae, and Staphylococcus aureus isolates, collected randomly at the National Taiwan University Hospital (NTUH) were studied. Bacterial isolates were mostly isolated from the blood and were collected from both outpatients and inpatients in different wards. Isolates were stored in Mueller–Hinton broth with 15% glycerol and frozen at −80 °C. Extended-spectrum beta-lactamase (ESBL)-production of the bacteria was detected by the recommended phenotypic confirmatory test (Clinical and Laboratory Standards Institute, 2016).
2.5. Susceptibility testing The minimal inhibitory concentrations (MICs) of each antimicrobial agent for the tested bacterial isolates were determined once by the agar dilution method according to the Clinical Laboratory Standards Institute (CLSI). (Clinical and Laboratory Standards Institute, 2016) All MIC tests were repeated. If discrepancies of results occurred between the 2 tests, a third test was performed. For each isolate, variation was calculated by one minus the ratio of MIC of levofloxacin from each company (MICc) divided by the MIC (MICs) of USP Levofloxacin RS [1-(MICc/MICs)]. (Jones et al., 2008) Mean variation was calculated by the sum of variations for the same organism divided by the number of the same organism.(Jones et al., 2008) With the use of a Steers replicator, 10 4 colony-forming units (CFU) of bacteria were inoculated onto Mueller– Hinton agar plates containing a series 2-fold dilution of antimicrobial agents. Following inoculation, the agar plates were incubated at 35 °C in 5% CO2 for 18–20 h. The MIC was defined as the lowest concentration of antimicrobial agent that completely inhibited the growth of bacteria.
The dissolution test was performed for 3 oral generic formulations (Generic A, B, D) and brand-name levofloxacin (Daiichi Sankyo) in acid buffer (pH = 1.2) (Fig. 1). The f2 values, the indicator of the similarity of dissolution curves between generic and brand-name tablets, were shown in Table 2. Generic A and B had different dissolution results in acid solutions with that from brand-name levofloxacin (Table 2). 3.3. Susceptibility testing The MIC ranges and mean variations of the 3 parenteral generic formulations (Generic A, B, C) and brand-name levofloxacin (Daiichi Sankyo) compared with USP levofloxacin RS are presented in Tables 3, 4 and Fig. 2. Compared with the 3 generic levofloxacin, the brandname levofloxacin had similar MIC ranges as USP levofloxacin RS did and had the smallest mean variations (−25% to +13%) compared with USP levofloxacin RS. The mean variations of the 3 generic levofloxacin were 0% to −50%, −160% to +25%, and −50% to +19%, respectively (Table 4 and Fig. 2). 4. Discussion We demonstrated that the purity of the 3 generic levofloxacin were similar with that of brand-name levofloxacin. However, variations in dissolution curves and in vitro antimicrobial activity against clinically significant pathogens were observed. Different additives in generic drugs despite the same ingredients as those of the brand-name drug might explain our findings (Agudelo et al., 2014). Differences in in vitro antimicrobial activity between generic and brand-name drugs have also been reported in other studies (Fujimura and Watanabe, 2012; Jones et al., 2008). A study showed a decrement of average 16% activity for 23 tested piperacillin/tazobactam generic lots compared with brand-name product (Jones et al., 2008). Another study also demonstrated that the potency of the generic products of vancomycin and
Table 3 Minimal inhibitory concentration (MIC) ranges of brand-name (Daiichi Sankyo) and 3 generic parenteral levofloxacin compared with that of USP levofloxacin RS. Organism
No. of isolates
Reference standard
Brand-name levofloxacin
Generic A
Generic B
Generic C
Pseudomonas aeruginosa Resistant Pseudomonas aeruginosa Acinetobacter baumannii MDR Acinetobacter baumannii Stenotrophomonas maltophilia Resistant Stenotrophomonas maltophilia Burkholderia cepacia complex Resistant Burkholderia cepacia complex Escherichia coli ESBL Escherichia coli Klebsiella pneumoniae ESBL Klebsiella pneumoniae Staphylococcus aureus Staphylococcus aureus (MRSA)
16 4 10 10 16 4 18 2 14 6 16 4 11 9
0.125–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.25 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.25 8–64
0.125–2 32–128 0.06–0.5 8–64 1–2 4–6 1–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.25–0.5 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.125–0.5 8–64
0.25–2 32–128 0.06–0.25 8–64 0.5–2 4–6 0.5–4 32–64 0.03–0.5 8–64 0.06–2 8–16 0.25 8–64
Abbreviations: ESBL, Extended-spectrum beta-lactamase; MDR, multi-drug resistant; ESBL, MIC, minimal inhibitory concentration; MRSA, methicillin-resistant Staphylococcus aureus; NA, not applicable; No., number; RS, reference standard; USP Pharmacopeia.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
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H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
Table 4 Mean MIC variations of brand-name (Daiichi Sankyo) and 3 generic parenteral levofloxacin compared with that of USP levofloxacin RS. Definitions: For each isolate, variation was calculated by one minus the ratio of MIC of levofloxacin from each company (MICg) divided by the MIC (MICu) of USP Levofloxacin RS [1 − (MICg/MIGu)]. Mean variation was calculated by the sum of variations for the same organism divided by the number of the same organism. Organism
No. of isolates
Brand-name levofloxacin
Generic A
Generic B
Generic C
Pseudomonas aeruginosa Resistant Pseudomonas aeruginosa Acinetobacter baumannii MDR Acinetobacter baumannii Stenotrophomonas maltophilia Resistant Stenotrophomonas maltophilia Burkholderia cepacia complex Resistant Burkholderia cepacia complex Escherichia coli ESBL Escherichia coli Klebsiella pneumoniae ESBL Klebsiella pneumoniae Staphylococcus aureus Staphylococcus aureus (MRSA)
16 4 10 10 16 4 18 2 14 6 16 4 11 9
13% 0% −10% 0% −6% 0% 0% 0% −7% 0% 6% −25% 0% 0%
0% 0% −50% −10% −25% 0% −17% 0% −7% 0% −31% −25% −18% −11%
25% 0% −30% −160% −50% 0% 0% 0% −29% 0% 0% −25% −9% −22%
19% 0% −40% −30% −50% 0% −6% 0% −21% 0% 0% −25% −9% 0%
Abbreviations: ESBL, Extended-spectrum beta-lactamase; MDR, multi-drug resistant; ESBL, MIC, minimal inhibitory concentration; MRSA, methicillin-resistant Staphylococcus aureus; NA, not applicable; No., number; RS, reference standard; USP Pharmacopeia.
Hatch-Waxman Act Drug Price Competition and Patent Term Restoration Act of 1984, 1984. Public Law 98–417, 98 Stat. 1585–1605," 1984; Frank, 2007). This Act obviated the necessity of conducting clinical trials for generic manufacturers to show the same safety and efficacy tests as brand-name manufacturers, but required bioequivalence to the active ingredients of the original brand-name drugs (Frank, 2007). Drug peak plasma concentration and area under the plasma drug concentration versus time curve, presenting drug rate and extent of absorption, respectively, are bioequivalence measures (Davit et al., 2009). Dissolution testing (The Ministry of Health, LaW, 2006) and highperformance liquid chromatography assay for purity (Nambiar et al., 2012) are also used to compare generic and brand-name drugs by some authorities. The US FDA reviewed 12 years of bioequivalence data, including 2070 single-dose clinical bioequivalence studies of orally administered generic drug products from 1996 through 2007, and concluded that the generic drug formulations are therapeutically equivalent to their brand-name counterparts (Davit et al., 2009). Nevertheless, another study in Japan noted different dissolution profiles between generic and brand-name drugs (Maezawa et al., 2013). In addition to the bioequivalence studies, numerous methods have been employed to assess whether generic antibiotics performed well
teicoplainin is lower than that of the branded drugs by 14.6% and 17.3%, respectively (Fujimura and Watanabe, 2012). Thus, hospital formularies should be cautious when applying generic products. Worldwide use of generic drugs has become a trend because generic drugs can significantly decrease drug expenses in national medical expenditures (Generic Pharmaceutical Association, 2012; Hughes and Ferner, 2010). In UK, the rate of generic prescribing has risen from 35% in the community in the mid-1900s to 83% in 2008 (NHS Information Centre, PSU, 2009). Furthermore, the Health (Pricing and Supply of Medical Goods) Act 2013 commenced on the Jun 24, 2013 was legislated to establish a list of groups of interchangeable medicinal products which may be substituted for each other in order to enable savings to be made for patients or the Health Service Executive, or both (Department of Health, 2013), and annual savings of 72 million pounds are expected after the implement of this act (Hughes and Ferner, 2010). Likewise, generic drugs account for only 18.6% in 1984, but 63% of all US prescriptions for drugs in 2007 (Frank, 2007), and have saved the US health care system approximately 1.07 trillion from 2002 through 2011 with 192.8 billion in savings achieved in 2011 (Generic Pharmaceutical Association, 2012). Such changes could be attributed to the Drug Price Competition and Patent Restoration Act of 1984, or the
-0.64% -1.11% -0.82% -0.04%
total -40% -40%
Variation All S. maltophilia
-20%
-5%
Variation All B. cepacia
-15%
Variation All KP
0%
0% -15% -15%
-5% 0%
Variation All P. aeruginosa
0% -15% -20%
Variation All E. coli Variation All AB
0%
-5% -5%
-30%
Variation All S. aureus
-95%
-100%
Generic C Generic B Generic A Brand-name
-5%
15% 20% 10%
-5% -5%
-35% -30%
-80%
-60%
-40%
-5%
-20%
0%
20%
Fig. 2. Mean variations of brand-name and 3 generic levofloxacin compared with that of USP levofloxacin RS for test bacterial isolates. MIC, minimal inhibitory concentration; AB, Acinetobacter baumannii; KP, Klebsiella pneumoniae, reference standard; USP, US Pharmacopeia.
Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015
H-Y. Sun et al. / Diagnostic Microbiology and Infectious Disease xxx (2016) xxx–xxx
as the brand-name ones, such as in vitro antibacterial potency against the target bacteria by MIC (Fujimura and Watanabe, 2012; Jones et al., 2008), in vivo efficacy by bactericidal efficacy (Vesga et al., 2010), the neutropenic mouse infection model (Rodriguez et al., 2010; Zuluaga et al., 2010), neutropenic guinea pig infection model (Agudelo et al., 2014) and rabbit endocarditis model (Tattevin et al., 2013). Some results demonstrated that bioequivalence of generic products of antibiotics do not guarantee therapeutic equivalence evaluated by neutropenic animal models (Agudelo et al., 2014; Rodriguez et al., 2010; Vesga et al., 2010; Zuluaga et al., 2010), but some did not (Rodriguez et al., 2015; Tattevin et al., 2013). Thus, therapeutic equivalence could not be reliably predicted from pharmaceutical equivalence of generic products. Judicious use of generic antibiotics is recommended given the benefit of reduced cost and the drawback of possible therapeutic nonequivalence. There are some limitations in our study to be acknowledged. First, we only tested generic levofloxacin by 3 manufacturers in Taiwan. However, given being the top 3 in the market, it is reasonable to test generic levofloxacin produced by these 3 manufacturers. Second, we employed only enantiomeric purity test, dissolution test, and in vitro activity against clinically significant pathogens to assess the similarity between generic and brand-name levofloxacin, but not animal models or post-marketing clinical study on healthy volunteers. Because differences in in vitro activity have existed, it is possible that differences in in vivo activity also existed. Further comparisons in animal models and prospective clinical studies are warranted. Lastly, we did not measure additives in both generic and brand-name drugs which might explain our findings. In summary, we have shown the differences in in vitro antimicrobial activity against clinically significant pathogens and dissolution test between generic and brand-name levofloxacin. Periodic monitoring of manufacture lots and therapeutic response of patients treated with generic levofloxacin are suggested. Acknowledgement This work was funded by Daiichi Sankyo, Inc.. The funder had no role in study design, data collection and interpretation, or the decision to submit the work for publication. References Agudelo M, Rodriguez CA, Pelaez CA, Vesga O. Even apparently insignificant chemical deviations among bioequivalent generic antibiotics can lead to therapeutic nonequivalence: the case of meropenem. Antimicrob Agents Chemother 2014;58:1005–18. Berg MJ, Gross RA, Tomaszewski KJ, Zingaro WM, Haskins LS. Generic substitution in the treatment of epilepsy: case evidence of breakthrough seizures. Neurology 2008;71: 525–30. Bureau of National Health Insurance, DoH, Executive Yuan. Universal Health Coverage in Taiwa; 2012. Clinical and Laboratory Standards Institute. Clinical and Laboratory Standards Institute (CLSI) Performance standards for antimicrobial susceptibility testing. 26th informational supplement; 2016. Davit BM, Nwakama PE, Buehler GJ, Conner DP, Haidar SH, Patel DT, et al. Comparing generic and innovator drugs: a review of 12 years of bioequivalence data from the United States Food and Drug Administration. Ann Pharmacother 2009;43:1583–97.
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Please cite this article as: Sun H-Y, et al, Bioequivalence and in vitro antimicrobial activity between generic and brand-name levofloxacin, Diagn Microbiol Infect Dis (2016), http://dx.doi.org/10.1016/j.diagmicrobio.2016.04.015