Iontophoresis of micellar composition of Lovastatin: Study of affecting factors and in-vitro permeation

j o u r n a l o f p h a r m a c y r e s e a r c h 7 ( 2 0 1 3 ) 3 2 7 e3 3 0

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Original Article

Iontophoresis of micellar composition of Lovastatin: Study of affecting factors and in-vitro permeation Jayrajsinh I. Sarvaiya a,*, Gourishankar K. Kapse b, Chintan J. Tank c a

Research Scholar, Department of Pharmacy, NIMS University, Jaipur, Rajasthan 302004, India Professor, Dakshin Solapur Taluka Shikshan Mandals College of Pharmacy, Solapur, Maharashtra 413001, India c Associate Professor, Pharmaceutical Research Centre, Noble Group of Institutions, Junagdh, Gujarat 362001, India b

article info

abstract

Article history:

Aim: The work was aimed to study in-vitro skin permeation of Lovastatin from Dodecyl-

Received 7 March 2013

trimethylammonium bromide (DTAB) containing micellar compositions by Iontophoresis.

Accepted 18 April 2013

Methods: Critical micelle concentrations (CMC) of DTAB in double distilled water containing

Available online 16 May 2013

Lovastatin were determined in various temperature conditions by conductometry to identify required minimum concentration of DTAB for preparation of stable micelles and

Keywords:

optimum solubility of Lovastatin. Micellar compositions were studied for the effect of two

Iontophoresis

vehicle systems and effect of two Iontophoresis operation factors, current strength and

Statin

type of current. In-vitro permeation study was carried out by using isolated rat skin to

DTAB

identify optimized formulation. Zeta potential, pH, assay of active ingredient and in-vitro

Micellization

permeation rate were studied during accelerated stability study of selected composition.

In-vitro permeation

Result: Maximum CMC value DTAB found to be 3.87
103 mol/L at 40  C. Accordingly, 0.0106 gm of DTAB was used per 100 ml composition which is above CMC value of DTAB at ambient room temperature. Phosphate buffer pH 7.4 as vehicle provided higher drug flux in comparison of salt containing solution as vehicle. Non-liners increase in drug permeation was observed when current density was increase from 0.1 to 0.5 mA/cm2. Continuous DC current provided significant high drug permeation from micellar composition in comparison of pulsed DC current. Conclusion: Lovastatin, a lipophilic drug can be delivered through skin effectively by Iontophoresis by using 0.5 mA/cm2 pulsed DC current from cationic surfactant containing composition. Copyright ª 2013, JPR Solutions; Published by Reed Elsevier India Pvt. Ltd. All rights reserved.

1.

Introduction

Lovastatin is one of the widely accepted HMG CO-A reductase inhibitor suggested for prescription by various government healthcare agencies.1 This first identified statin drug faces problem of lower bioavailability due to high lipophilicity and

short half life. Myopathy is one of the potential side effects of Lovastatin which is observed extensive in case of concurrent oral administration of statin drugs.2 These potential problems can be easily overcome by using transdermal delivery of Lovastatin but previously reported problem of crystallization of many statins in polymers used in transdermal drug delivery

* Corresponding author. Tel.: þ91 9638344845. E-mail address: [email protected] (J.I. Sarvaiya). 0974-6943/$ e see front matter Copyright ª 2013, JPR Solutions; Published by Reed Elsevier India Pvt. Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jopr.2013.04.032

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system is the matter of concern in controlled and precise delivery of statin drugs through such dosage forms.3 Iontophoresis is generally possible for transdermal delivery of ionized drug molecules. Many investigators have reported possibility of Iontophoresis of non-ionic lipophilic drugs by artificially generation of charge on drug molecule by use of surfactants or charge coupling by complexation.4 Micellar solubilization of drug by ionic surfactant can fulfil two aspects, one is charge generation and the other is drug solubilization. Dodecyltrimethylammonium bromide (DTAB) is a cationic surfactant. It is preferred for transdermal delivery because an anionic surfactant may damage skin more adversely than a cationic surfactant.5 Moreover, small molecular weight of DTAB (w285 Da) in comparison of other quaternary ammonium cationic surfactants make it a preferred surfactant for micelle formation for delivery of Lovastatin. The present work was aimed to investigate effect of DTAB micelles on Lovastatin permeation through skin during Iontophoresis. Study of potential formulation factors and operational factor was also intended during Iontophoresis of selected lipophilic drug.

extent. Effect of various temperature conditions, room temperature (25  C), operational temperature (37  C) and accelerated stability study condition (40  C) were studied on CMC of DTAB.

2.2.2.

Formulation compositions

Solution of Lovastatin in double distilled, deionized water containing 10% v/v PEG 400 was used as control standard. This solution was used for passive in-vitro permeation study by mounting isolated rat skin as partitioning membrane. Modified Glickfeld diffusion cells were used for 12 h in-vitro Iontophoresis study presented in this research work.6

2.2.2.1. Compositions for study of effect of different vehicles on Iontophoresis. Enhancement ratio of in-vitro permeation of Lovastatin was studied by using three vehicle compositions as mentioned in Table 1. Iontophoresis of three compositions LVI 1, LVI 2 and LVI 3 was carried out by using DC power source (Mfg by Chromtech ltd, Thane, India). Silver/silver chloride electrodes were used in this Anodal iontophoretic experiments. 0.25 mA/cm2 density continuous current supply was kept as constant process parameters.

2.2.2.2. Compositions for study of effect of current density.

2.

Materials and methods

2.1.

Materials

Lovastatin was obtained as gift sample from hetero drugs (Hyderabad, India). DTAB was purchased from sigma Aldrich (Mumbai, India). Sodium chloride, Sodium hydroxide, Polyethylene glycol (PEG 400) and potassium dihydrogen phosphate were purchased from Astron Chemicals (Ahmedabad, India). Organic solvents used were of HPLC grade and obtained from Merck India (Mumbai, India).

Selected composition among LVI 1, LVI 2 and LVI 3 was used to study effect of three different current strengths on in-vitro Lovastatin permeation by Iontophoresis. 0.1, 0.25 and 0.5 mA/cm2 current densities were used as variable condition in Iontophoresis while keeping current pattern as continuous DC current.

2.2.2.3. Compositions for study of effect of current patterns.

2.2.

Experiments

DTAB micellar solution containing Lovastatin in phosphate buffer pH 7.4 was charged in donor compartment of modified Glickfeld diffusion cell. In one experiment, 0.5 mA/cm2 DC current source was kept in continuous mode and in the other experiment it was kept in 10 s on/off (pulsed) mode.

2.2.1.

Preformulation studies

2.2.3.

Solubility of Lovastatin was determined in solution containing critical micelle concentration of DTAB to fix the drug loading

In-vitro permeation study

Ten to twelve week old male albino rats (250 g) were sacrificed by excess of ether inhalation. After removing hairs, full-

Table 1 e Compositions for study of effect of various solvents. Composition code

Composition (100 ml)

Parameters Current density (mA/cm2)

Study of effect of solvent system Control (Passive diffusion) LVI 1 LVI 2 LVI 3 Study of effect of different current LVI 4 LVI 5 LVI 6 Study of effect of different current LVI 7 LVI 8 LST : Lovastatin.

0.1 mg LSTþ10 ml PEG400 þ q.s. water 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. water 0.1 mg LSTþ(3.87
103)mM DTAB þ0.1 M NaCl þ q.s. water 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer strengths 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer patterns 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer 0.1 mg LSTþ(3.87
103)mM DTAB þ q.s. phosphate buffer

Current pattern

e 0.25 0.25 0.25

Continuous Continuous Continuous

0.10 0.25 0.50

Continuous Continuous Continuous

0.50 0.50

Continuous Pulsed

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thickness of rat abdomen skin was surgically removed. The rat epidermis was isolated by a heat separation technique and carefully cleaned with normal saline. Finally fat tissue adhered to skin removed by wiping it with cotton swab soaked in isopropyl alcohol and dried under the vacuum followed by storing in desiccators.7e9 Skin samples were used within three days of isolation. Protocols for the use of animal for the above experiment was previously approved from the Institutional animal ethics committee, Noble Group of Institutions, Junagadh. Iontophoresis experiments were carried out at 37  2  C. All analytical works for quantification of Lovastatin were done by validated RP-HPLC analytical method by using 0.1% phosphoric acid solution and acetonitrile (65:35 v/v) as mobile phase.

2.2.4.

Stability study

Selected composition was charged for stability study under accelerated stability study condition as per ICH guideline. Selected composition was studied for Zeta potential determination, pH and assay of Lovastatin and in-vitro permeation rate.

2.3.

Results and discussion

2.3.1.

Preformulation study

DTAB was selected as a surfactant for composition for Iontophoresis experiments because single surfactant micelle possesses best solubilizing power than mixers of surfactants specially in context of micellar solubilization of drugs.10 Solubility of Lovastatin was found to be 0.1 mg in 3.7
103 mol/L of DTAB which is more than 230 folds generally observed in purified water. Fig. 1 show CMC of DTAB in 0.1 mg Lovastatin containing solution under various temperature conditions and it was evidenced that the maximum shift of CMC was up to 3.87
103 mol/L at 40  C. So, use of 3.87
103 mol/L DTAB in composition can keep Lovastatin in soluble form in core of liquid crystals formed by micelles of DTAB.

2.3.2. Effect of various factors on in-vitro permeation of Lovastatin Passive diffusion of Lovastatin allowed 3.63  0.10 mg/cm2/ h Lovastatin permeation rate after 12 h Iontophoresis with

Fig. 1 e Conductometric determination of CMC of DTAB in Lovastatin containing solution under various temperature conditions.

Table 2 e In-vitro permeation study data by Iontophoresis of different compositions. Composition Q24 (mg/cm2) Jss (mg/cm2/hr) k(cm/hr) E.R. Control LVI 1 LVI 2 LVI 3 LVI 4 LVI 5 LVI 6 LVI 7 LVI 8

44.36 72.32 69.43 89.98 66.59 77.87 120.42 118.43 211.36

 4.02  4.10  4.85  4.72  4.12  3.85  5.98  5.21  10.0

3.63  0.10 6.10  0.48 5.60  0.71 6.58  0.70 6.12  0.45 6.47  0.42 11.06  0.70 10.94  0.71 19.47  1.81

0.0036 0.0061 0.0058 0.0065 0.0061 0.0064 0.0110 0.0109 0.0194

1 1.68 1.59 1.81 1.68 1.78 3.04 3.00 5.35

Q24: Cumulative drug permeated, Jss: Steady state flux, k: Diffusion coefficient, E.R: Enhancement ratio. Values presented are mean  s.d; n ¼ 3.

44.36  4.02 mg/cm2 cumulative permeation of drug. Phosphate buffer pH 7.4 as vehicle system provided highest drug permeation with Permeation Enhancement Ratio (E.R.) 1.80 in comparison of passive diffusion (Table 2) (Fig. 2). Lesser E.R. was observed in case of NaCl containing solution may be due to counter ion effect produced by Cl of NaCl on DTAB micelles. Effect of counter ions can be more above CMC of surfactant leading to rapid change in zeta potential of micelle containing composition.11 Lovastatin solubility in water is slightly high in alkaline pH and absence of effective counter ions for DTAB micelles contributed in high E.R of LVI 3 composition. Lovastatin permeation rate was increased by increase in current density in Iontophoresis study. E.R. under influence of 0.5 mA and 0.1 mA was obtained 3.07 and 1.7 respectively. It depicted high current density requirement for transportation of DTAB liquid crystals to skin surface and skin pores. Here generation of convective flow was evaded under influence of high current strength and corresponding micelle mobilization. Iontophoresis delivery is generally considered safe against skin burn with 0.5 mA current density as ceiling limit of current exposure hence study in current strength above 0.5 mA was futile.12 Skin is considered as a ‘parallel resistor-capacitor’ model which is capable of neutralizing effect of pulsed and continuous current effects on most of the ionic drugs.13 Lovastatin permeation plot of experiment under pulsed current obtained and

Fig. 2 e Comparative drug permeation profile of different compositions by iontophoresis.

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Table 3 e Accelerated stability study results of LVI 8 composition.

Acknowledgement

Assay of active ingredient (%)

We acknowledge financial support of Shakti Pharmatech Pvt Ltd, Ahmedabad, India and analytical testing support by Sophisticated Analytical Instrumentation Facility centre (SAIF), Saurashtra University, Rajkot, India.

pH

Zeta potential (mV)

Initial observation (of unconstrained samples) 101.25 ± 0.2 7.4 þ 47 Observations after 10 days 101.20 ± 0.1 7.4 þ 47 Observations after 30 days 99.83 ± 0.2 7.4 þ46 Observations after 60 days 99.71 ± 0.4 7.4 þ46 Observations after 90 days 99.05 ± 0.6 7.4 þ44

In-vitro drug Permeation (mg/cm2/hr) 19.47  0.84 19.54  0.97 19.01  1.03 18.98  1.01 19.11  1.10

Values presented in assay of Lovastatin and flux study are mean  s.d; n ¼ 3.

presented in Fig. 2 highlight different relation of skin than skins electromigration neutralization capacity by showing significant high Lovastatin permeation in presence of pulsed current (LVI 8). High drug flux might be due to counter of enhanced skin depolarization by 10 s ‘off’ mode in Iontophoresis.

2.3.3.

Stability study

Zeta potential is not only colloidal system stability marker but it is indicator of micelles solubilization capacity towards lipophilic drugs and oily matters.14 Stability study results have shown very slight change (decreased from þ47 to þ44) in zeta potential of micellar composition indicating negligible aggregation of micelles which is quite possible in absence of electrolytes as colloid stabilizers (Table 3). The slight change in zeta potential did not affect drug permeation profile significantly (p < 0.05). Other studied parameters were remained almost constant indicating stability of Lovastatin in DTAB micellar composition.

2.4.

Conclusion

Lovastatin, a lipophilic drug can be delivered through skin effectively by Iontophoresis by using 0.5 mA/cm2 pulsed DC current from cationic surfactant containing composition. Presence of electrolyte as counter ion negatively effects permeation of drug from micellar composition during Iontophoresis.

Conflicts of interest All authors have none to declare.

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