Kinetic disposition, systemic bioavailability and tissue distribution of apramycin in broiler chickens

Research in VeterinaryScience 1997,62, 249-252

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Kinetic disposition, systemic bioavailability and tissue distribution of apramycin in broiler chickens N. A. AFIFI, A. R A M A D A N , Department of Pharmacology, Faculty of Veterinary Medicine, Cairo University, Giza,

P.O. Box 12211, Egypt

SUMMARY Apramycin was administered to chickens orally, intramuscularly and intravenously to determine blood concentration, kinetic behaviour, bioavailability and tissue residues. Single doses of apramycin at the rate of 75 mg kg-1 body weight were given to broiler chickens by intracrop, i.m. and i.v. routes. The highest serum concentrations of apramycin were reached 0.20 and 0.76 hours after the oral and i.m. doses with an absorption half-life.. .(t~ (ab.)) of 0.10 and 0-19 hours and . an. elimination . . half life (t~ t~) ) of 1.22 and 2.31 hours respectively. The systemic bioavadabdlty was 2.0 and 58 per cent after lntracrop and 1.m. administration, respectively, indicating poor absorption of the drug when given orally. Following i.v. injection, the kinetics of apramycin was described by a two-compartment open model with a (t)(a)) of 1.5 hours, (tl~(j3)) of 2.1 hours, Vd(ss) (volume of distribution) of 4-82 litre kg-1 and CI(B) (total body clearance) of 1-88 litre kg-1 hour -1. The serum protein-binding of apramycin was 26 per cent. The highest tissue concentrations of apramycin were present in the kidneys and liver. No apramycin residues were detected in tissues after six hours except in the liver and kidneys following intracrop dosing and kidneys following i.m. administration.

A P R A M Y C I N is an aminocyclitol broad spectrum antibiotic used for the treatment of systemic and enteric infections in a variety of species of animals. It is generally not well absorbed from the gastrointestinal tract of animals (Thomas et al 1991). Extensive studies concerning the rate of absorption, distribution and elimination of various aminoglycosides in veterinary practice have been carried out by many investigators (Podkopaev 1974, Beech et al 1977, Baggot 1978a, Riviere and Coppoc 1981, Ziv et al 1985, Shikha 1987, Pashov 1988, Aziz et al 1988, Aziza et al 1994). The extensive use of the orally administered aminoglycosides and aminocyclitols such as apramycin for treatment of enteric infectious diseases in poultry and the medical problems caused by their residues in meat, necessitates studies on the disposition of this drug in chickens. The present study was conducted to describe the ldnetic disposition, bioavailability, tissue distribution and the residual content of apramycin in chickens after oral, i.m. and i.v. dosing.

MATERIALS AND METHODS

Drug Apramycin sulphate (Apra 200(R)) was supplied by Eli Lilly, Italia.

Birds Seventy clinically healthy Hubbard chickens with body weights of 1.65 to 1.75 kg and 45-50 days old, were obtained one week before the study began. During acclimatisation and subsequent treatment periods, they were fed antibacterial-free balanced commercial rations and drinking water was freely available. The birds were housed in groups of five per cage. 0034-5288/97/030249 + 04 $18.00/0

Experimental design Pharmokinetic studies. Ten chickens were placed into two groups of five. Chickens from the first group were administered a single dose of apramycin (75 mg kg -1 body weight) orally via intracrop, and those of the second group received the drug intramuscularly. Blood samples were obtained from the wing vein before and at 15 and 30 minutes and one, two, three, four, five, six, eight, 12 and 24 hours after administration to determine the drug concentration in serum. About 1 ml of blood was collected at each sampling time. Apramycin was injected intravenously to the above chickens two weeks later at the same dose rate to study the drug bioavailability. Samples were allowed to clot and then centrifuged to obtain serum to determine the apramycin concentration and serum protein binding percentage on the same day as sample collection.

Tissue distribution. Sixty birds were divided into two equal groups of 30 birds each. Birds of the first and second group were administered apramycin (75 mg kg -1 body weight) daily for five successive days via intracrop and i.m. routes, respectively. Five chickens were slaughtered from each group at 15 minutes, one, three, six, 12 and 24 hours after the last dose was administered. Blood and tissue samples (liver, kidney, lung, brain, intestine and breast muscle) were taken from the slaughtered birds. Blood samples were centrifuged to separate serum to determine the apramycin concentration. One gram of tissue was homogenized in 3 ml of distilled water, left to stand overnight at 4°C and was then centrifuged at 1600 rpm for 10 minutes. Analytical methods. Apramycin in blood and tissue samples was determined by the microbiological method described by Bennett et al (1966) using Bacillus subtilis (ATCC 6633) as test organism. The present study revealed that the limit of quantification of apramycin in both serum and tissues are 0.02 ~tg m1-1 and 0.05 ~tg g-l, respectively. © 1997 W. B. Saunders CompanyLtd

250

N. A. Afifi, A. Ramaclam

The serum protein binding of the drug was determined in vitro utilising the method of Lorian (1980). The percentage of protein-bound fraction was calculated as follows: Conc. of apramycin bound to serum protein

Protein binding _ percentage

x

100

Conc. of apramycin in the standard solution

calculations. The pharmacokinetic parameters of apramycin in chickens were calculated according to the method of Baggot (1978b). The oral and i.m. availability of apramycin (F %) was calculated from the ratio between the value of AUG oral and/or i.m. for each individual chicken and the value of AUG i.v. for the same individual chicken used in the i.v. administration study. Results were expressed as m e a n (SEM). Pharmacokinetic

RESULTS

Pharmacokinetics

Results of serum concentrations of apramycin after a single oral, i.m. and i.v. administration of 75 mg kg -1 body weight were shown in Fig 1. Values for kinetic constants describing the absorption and disposition of the drug in chickens after oral, i.m. and i.v. administration are incorporated in Table 1. Following i.v. injection, the drug concentration revealed a biexponential decline that can be described by a two-compartment open model. The drug was rapidly distributed and eliminated with an elimination half-life of 2-10 _+ 0.01 hours. The apparent volume of distribution exceeded one litre per kg body weight. By oral and i.m. administration, the absorption half-life and their corresponding tmax. revealed rapid absorption. The bioavailability of apramycin after oral and i.m. administration was 2-03 + 0.02 and 58-0 + 1.57 per cent, respectively (Table 1). The protein binding for apramycin was 26.0 + 2-82 per cent. Tissue distribution

,

0.1

I

,

I

1

0

,

2

,

I

3

The concentrations of apramycin in serum and tissues of slaughtered birds after a multiple intracrop dosing are presented in Table 2. The kidneys had the highest concentration followed in order by the liver, lung, intestine, breast muscle and brain. No residues were detected in lung, intestine, breast muscle and brain after 6 hours, and in liver and kidneys after 12 hours, following intracrop dosing. Results of apramycin concentrations in the serum and tissues of birds administered intramuscularly with the drug daily for five successive days are shown in Table. 3. The highest concentration of apramycin residues were present in the kidneys followed by liver, lung, breast muscle, intestine and brain. No residues could be detected in either serum or tissues, with exception of kidneys, after 24 hours. No apramycin residues could be detected in intestine and brain after 12 hours.

I

4

10

I.M.

o

TABLE 1 : Pharmacokinetic parameters of apramycin in chickens after a single i.v., i.m. and o r al administration of 75 mg kg- 1 body weight. o

0.I L

0

-

.

~

2

4

6

8

10

12

I00

I.V.

0.1 ~ 0

2

4

6 8 T i m e (hours)

10

12

FIG 1: Semi-logarithmic graph depicting the time-concentration course of apramycin in serum of chickens after a single oral, I.M and I,V. administration of 75 mg kg -1 body weight

Parameter

Unit

C° A o~ t~(a) K(aS.) t~(ab.) tmax. Cmax. B 13 Kel t~(13) 12 K21 Ve Vd (area) Vd (1~) Vd (B) Vd(ss) A.0_oCltB~.

gg m]--1 16.00 (0.32) gg m1-1 9,62 (0.25) hour I 0.46 (0.01) hour 1.50 (0.20) hour "1 hour hour gg ml "1 gg m1-1 6.38 (0.53) hour 1 0.34 (0.01) hour 1 0.40 (0.003) hour 2-10 (0-01) hour 1 0.01 (0.002) hour 1 / 0.39 (0.01) litre kg -1 4.70 (0.09) litre kg "1 5,62 (0-14) litre kg 1 5.62 (0.14) litre kg -1 12.09 (1.01) litre kg -1 4,82 (0.08) litre kg -1 h "1 1.88 (0-05) gg m1-1 h -1 39.93 (1.02) %

F

i.v. (n = 10)

Oral (n = 5)

i.m (n = 5)

6.66 (0.06) 0.10 (0,001) 0.20 (0.01) 0.79 (0.02) 0.41 (0.01)

3.60 (0.07) 0.19 (0.004) 0.76 (0,03) 11.06 (0.31) 6.46 (0.26)

1.21 (0.01) 1.22 (0.01)

0.53 (0.004) 2.31 (0,02)

0.81 (0.02) 2.03 (0,02)

23-18 (1.08) 58 (1.57)

AUC (oral & or i.m. for each chicken) F (%) = AUC (i.v. for each chicken) The results are the mean (SEM).

x 100

251

Apramycin in broiler chickens

TABLE 2: Serum and tissue concentrations of apramycin (pg ml "1 or g-l) after a multiple intracrop dose of 75 mg kg "1 body weight for five successive days in chickens (n = 5) Tissue 0.25 Serum Liver Kidney Lung Brain Intestine Breast muscle

0.86 (0.02) 0.31 (0.01) 1.32 (0.11) 0.27 (0.01) 0.10 (0-003) 0-18 (0.02) 0.14 (0-004)

Time of slaughter after the last dose (hours) 1 3 6 12 0.37 (0.01) 0.14 (0.01) 1.07 (0.02) 0.14 (0.01) 0.09 (0.002) 0.12 (0-01) 0.10 (0-003)

0-24 (0.01) 0.09 (0,002) 0.72 (0.01) 0-09 (0-001) 0-06 (0.001) 0.08 (0.01) 0-07 (0.003)

24

0.07

(0.002) 0.05

(o.ool) 0.48

(0-003)

- not detectable The results are the mean (SEM). TABLE 3: Serum and tissue concentrations of apramycin (pg ml "1 or g-l) after a multiple i.m. dose of 75 mg kg "1 body weight for five successive days in chickens (n = 5) Tissue 0.25 Serum Liver Kidney Lung Brain Intestine Breast muscle

3.93 (0.09) 1.65 (0.02) 7.06 (0-21) 1.38 (0-07) 0.51 (0.02) 0.65 (0.01) 0.72 (0.01)

Time of slaughter after the last dose (hours) 1 3 6 12 9.95 (0.24) 5.05 (0-08) 15.99 (0.44) 4.18 (0-08) 1-50 (0.02) 0.96 (0.01) 2.08 (0.07)

4.50 (0-09) 2.25 (0.08) 8.68 (0.27) 1.75 (0.04) 0.65 (0-01) 0-71 (0.03) 0.86 (0.03)

1.88 (0-05) 0.89 (0-02) 3.74 (0. I 0) 0.75 (0-02) 0.27 (0.01) 0-38 (0.02) 0.38 (0.004)

24

0.72 (0-02) 0.29 (0.01) 1,16 (0.05) 0-23 (0.01) -

-

-

-

0.11 (0.001)

-

0.63 (0,01) -

- not detectable The results are the mean (SEM).

DISCUSSION

Apramycin, an aminocyclitol antibiotic, has been recommended for the treatment of intestinal bacterial infections in animals (Pankhurst et al 1975, Moore and Ryden 1977, Walton 1978). The present study showed that the plasma concentrations of apramycin in chickens were greater than minimum inhibitory concentrations (MIC) of most sensitive organisms, which ranged from 1 to 8 pg m1-1 (Moore and Ryden 1977) till one to six and one to eight hours after i.v. and i.m. administration of 75 mg kg -1 body weight. On the other hand, Cruickshank et al (1975) considered that a bacterium may be sensitive to an antibiotic if the MIC is not more than ¼-~ of its average concentration in blood. Serum concentration data were best fitted to a two-compartment pharmacokinetic model after i.v. dosing with a distribution phase completed by 0.33 hours. Our findings are similar to those reported by Aziza et al (1994) in chickens and Ziv et al (1985) and Shikha (1987) in calves. Apramycin was rapidly distributed in tissues afer i.v. injection as indicated by the value of t~(c0 (1-5 hours). On comparing this value with those of other aminoglycosides, it showed relatively similarity (Chisholm et al 1968, Rodriguez et al 1971, Carbon et al 1978, Aziz et al 1988). The biological elimination half-life (t~(~)) of. apramycin, in chickens was 1.22, 2.31 and 2.10 hours after lntracrop, a.m. and i.v. administration. On comparing these values with those of other aminoglycosides, it showed relative similarity. The biological half-life

of gentamicin was 30 minutes (Luft and Kleit 1974) and 75 minutes in dogs (Baggot 1978b); 61 minutes in juvenile dogs (Riviere and Coppoc 1981); 2.54 hours in horses (Pedersoli et al 1980), and 1.61 hours in calves (Aziz et al 1988). This variation in elimination half-life of aminoglycosides in different species could be explained OH the basis of variation of protein binding capacity of different drugs in different species (Gorden et al 1972). The apparent volume of distribution at steady state of a drug (Vd(ss)) is an indication of its diffusion in body tissue (Gilman et al 1980). The mean Vd(ss) value in chickens was 4-82 litre kg -1. Apramycin showed high V c, volume of distribution Vd(ss) and V(area) (4.7, 4-8 and 5.6 litre kg q, respectively) in chickens. These values were similar to those observed by Aziza et al (1994) in chickens and by Shikha (1978), Ziv et al (1985) and E1-Gamal (1992) in calves. The relatively higher values of V c and Vd(ss) were indicative of a drug which was more extensively distributed in extravascular tissues. On .the other hand, apramycin showed a high body clearance rate (1.88 litre kg -1 h -1) in chickens which was consistent with its short elimination half-life value. Confirmation of this phenomenon was observed by higher CI(B ) values for some aminoglycosides in dogs in relation to their lower t~ values (Baggot 1978). These values were higher than values of aminoglycosides such as kanamycin (Baggot 1978a); gentamicin (Gyselycneck et al 1971, Pedersoli et al 1980, Riviere and Coppoc 1981) and apramycin (Aziz et al 1988) in dogs, horse, man and calves for which (CI(B)) values were 0.24, 0-25, 0.35 and 0.88 litre kg -1 h -1, respectively. The bioavailability of apramycin after i.m. injection in chickens was higher with approximately 58 per cent of it being absorbed. This value was similar to that observed by Aziz et al (1988) in calves, which ranged from 60 to 66 per cent and Aziza et al (1994) in chickens which was 85 per cent. On the other hand, the bioavallability of apramycin after intracrop administration was very low with approximately 2-03 per cent of the drug being absorbed. Similar results were reported by Thomson et al (1991) and Aziza et al (1994) who found that apramycin is normally not well absorbed from the intestinal tract of broiler chickens. The capacity of apramycin to bind with serum protein of chickens was only 26 per cent. The highest concentrations of apramycin were present in the kidneys and liver after daily intracrop and i.m. administration for five days. This observation was supported by Thomson et al (1991). The high volume of distribution and low protein binding of this drug in chickens is reflected by its persistance in tissues for a longer time. This is due to the shorter half-life of drug elimination. In conclusion, poultry farms must give at least two days premarketing withdrawal time for apramycin to ensure that the drug is eliminated from the tissues.

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Received February 27, 1996 Accepted November I4, 1996