Effect of Some Penetration Enhancers on In-vitro Permeation of Glibenclamide

 

SD Pande^*1, SB Joshi², SB Kasture³ and VM Aurangabadkar⁴

¹Department of Pharmaceutics, Vidyabharti College of Pharmacy, Amravati-444602              

²Deptt.of Pharm. Sciences, RTM Nagpur University, Nagpur, Maharashtra            

³Sanjivani College of Pharmacy, Kopargaon, Dist. Ahemdnagar Maharashtra        

⁴MGV’S Pharmacy College, Panchvati, Nashik, Maharashtra

*Corresponding Author E-mail: shrikantdpande@rediffmail.com

ABSTRACT:

Transdermal drug delivery system is one of the novel routes for systemic delivery of drugs through the skin. The main barrier for systemic absorption of drug through the skin is the upper most layer of skin i.e. the stratum corneum. Glibenclamide is a sulfonylurea category of drug used in the treatment of type II diabetes. It is found that glibenclamide can be permeated through the skin but its permeation is low. Therefore its permeation was studied through the freshly excised rat abdominal skin as such and in presence of some penetration enhancers. Penetration enhancers are the substances that facilitate the absorption of drug through the skin by temporarily diminishing the impermeability of the skin. In the present study permeation enhancers have been used to increase the permeation of glibenclamide through the freshly excised rat abdominal skin. The permeation enhancers used are eucalyptus oil, menthol, ethyl acetate and oleic acid respectively .It is found that eucalyptus oil has more effect as compared to other enhancers used in the study. The results are reported in this article.

 

 

 

INTRODUCTION:

The transdermal drug delivery system (TDDS) has some advantages as an alternative dosage form (i) avoiding first pass metabolism, (ii) easy discontinuation of administration, and (iii) reduced side effects; however, the stratum cornea, which is the outermost layer of skin, provides a primary barrier to transdermal drug delivery. Glibenclamide has action common to all sulfonylurea drugs. Their primary effect is to potentiate glucose stimulated insulin release from functioning pancreatic ß cells¹⁷⁷ Glibenclamide is widely used as a prototype potassium channel blocking agent. About 90 to 100% of drug is absorbed from gastrointestinal tract when given orally in micronized form and 64 to 90% in nonmicronized form. The plasma concentration reaches maximum after ingestion within 1.5 to 2 hrs.  It is found that high fiber diet reduces absorption of glibenclamide.  These drugs show erratic absorption via oral route and other reasons like higher frequency towards metabolism leading to one or more than one metabolites which may or may not be active (mostly inactive), Earlier work has demonstrated that glibenclamide has a permeation through skin.^1-4

 

MATERIALS AND METHODS:

Glibenclamide was obtained as a gift sample from M/s. Cadila Pharmaceuticals Ltd., Ankaleshwar. All other chemicals used were of analytical grade. The penetration enhancers used in the study were used as such. Diffusion studies were carried out for this purpose mentioned below.

 

Diffusion studies without using penetration enhancers:

In this study locally fabricated vertical glass diffusion cell having donor area 3.46 cm² and receptor cell volume 20 ml. was used. Freshly excised rat abdominal skin was used for this study. Samples of skin were removed from the abdomen. The skin was treated with 0.32 M ammonia solution for about 30 minutes; the hairs and fats were removed with the help of forceps. The skin was washed with warm water and examined for any cuts if any. The skin sample was then cut to size and held between the two halves of diffusion cell. The stratum corneum faced the donor compartment and the dermis faced the receptor compartment. The two compartments were held together tightly with the help of rubber bands which served as a clamps. The receptor compartment was filled phosphate buffer pH 7.4. The whole assembly was placed in a 250 ml. beaker containing water. This beaker was then placed over a magnetic stirrer with heating device. The temperature of water was kept at 37 + 2⁰ C. The receptor fluid was stirred with small magnetic bar. The buffer solution was replaced at the intervals of every half an hour.

 

 

Comparison of penetration enhancers used for Glibenclamide

Time in  Hour	Pure. Drug Cumm. Rel. In mcg/cm2	Eucal. Oil Cumm. Rel. In mcg/cm2	Menthol Cumm. Rel. In mcg/cm2	Oleic acid Cumm. Rel. In mcg/cm2	Ethyl Acetate Cumm. Rel. In mcg/cm2
1	0.00 ±0.00	0.20±0.17	0.00±0.00	0.00±0.00	0.00±0.00
2	0.32 ±0.52	5.30±1.20	0.12±0.07	0.00±0.00	0.16±0.05
3	0.86 ±0.72	17.32±2.87	0.40±0.28	0.27±0.030	0.35±0.14
4	1.45 ±0.56	45.13±4.6	10.47±0.98	1.11±0.090	0.67±0.32
5	2.59 ±1.02	96.75±6.10	33.76±3.40	7.39±0.57	1.64±0.76
6	7.65 ±2.12	164.85±7.69	81.57±5.76	22.09±1.44	6.38±2.10
7	14.94 ±4.28	257.52±11.13	145.99±9.17	47.89±3.17	14.54±4.50
8	24.06 ±5.76	368.27±15.40	217.85±8.44	105.57±8.16	29.81±6.54
9	35.78 ±5.61	526.79±13.03	312.01±7.68	177.73±7.86	61.48±8.81
10	51.78 ±8.60	716.93±15.12	421.67±10.14	272.13±14.52	111.9±12.01
11	71.18 ±7.32	952.38±19.43	578.27±14.32	387.5±17.23	181.04±14.35
12	94.11 ±9.41	1244.48±23.02	760.97±19.24	525.02±22.40	273.88±19.79

* Each value is an average of three measurements ± S.D.

 

 

The UV absorbance of receptor solution at the wavelength of estimation of drug was checked every time the sample was withdrawn. The process was repeated till the receptor solution showed negligible absorbance (it required about 3-4 hours). After it the skin sample was ready for experiment. This was done to avoid interference of the material from dermis. Rat abdominal skin having 3.46 cm² was cut. The skin sample was carefully mounted between donor and receptor compartments of vertical glass diffusion cell. A saturated suspension of drug in Phosphate buffer 7.4 placed in donor compartment. Samples were withdrawn from the receptor compartment for 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 hours. Every time a previously warmed Phosphate buffer was replaced with equal volume. The samples were analyzed spectrophotometrically at respective wavelength as mentioned previously.

 

Diffusion studies using penetration enhancers:

Penetration Enhancer Study: The Penetration enhancers used were from terpene class and chemicals which have got enhancement effect. Eucalyptus oil, menthol, oleic acid and ethyl acetate were used as penetration enhancers. For penetration enhancement study, skin samples of rat abdominal skin was treated first i.e. the neat penetration enhancer applied to skin (10%). Menthol was dissolved in small amount of ethanol and then 0.1 ml was applied (in 10% conc.) to skin. Other liquids enhancers were used as such and applied neat to rat abdominal skin. The penetration enhancers were applied neat only when the rat abdominal skin was clamped carefully in between two compartments with stratum corneum facing donor compartment and dermis facing receptor compartment. The saturated solution of drug was placed and the assembly put on magnetic stirrer as mentioned above. The samples (2ml) were withdrawn for 12 hours with an interval of one hour and equal volume replaced as done in control samples (without penetration enhancers). The samples were analyzed spectrophotometrically. A control was assigned a value of 1.00 the amount of drug diffused through the skin was plotted against time and readings shown in table.

 

RESULTS AND DISCUSSIONS:

In the present study menthol and eucalyptus oil has been used as a penetration enhancer and other two chemicals were oleic acid and ethyl acetate.  Rat abdominal skin was used for diffusion studies.  There is no one species of animals whose cutaneous diffusion barrier to a range of permeants has been shown identical to that of man. From a permeability point of view; the stratum corneum is big barrier which is similar to thickness in man and rat.  The rat epidermis and skin are two third as thick as human skin.  The relatively thick stratum corneum is due to composition of epidermis which is over 50% stratum corneum by thickness.  Though rat skin is more permeable than human skin, the ease and convenience of handling and low cost of animal made rat as a good model for the present study.

 

Eucalyptus oil is an essential oil used in medicines as analgesic.  Eucalyptus oil contains chiefly eucalyptol a terpene compound. It has been used as a penetration enhancer in different studies.^5-8  In the present study it was found to show best permeability for glibenclamide.  This was calculated by enhancement ratio calculated by formula.

 

                                     Amount permeated after treatment

                                     of enhancer in specific time

Enhancement ratio =   Amount permeated before treatment

                                      of enhancer in specific time

 

In the present study the enhancement ratio for Glibenclamide was found to be 13.2236 when eucalyptus oil was used as a penetration enhancer, while, menthol, oleic acid and ethyl acetate have enhancement ratios of   6.44, 5.54 and 2.91 respectively.  The order of decrease in enhancement of activity was found to be Eucalyptus oil >Menthol > Oleic acid > Ethyl acetate. Ethyl acetate was found to increase the permeation by nearly three times but all other enhancers used could increase the rate of permeation of glibenclamide at least more than five times. It has been suggested that mechanism of action of terpenes involves the disruption of intercellular lipids of stratum corneum.  It appears that for hydrophilic drugs, the primary effect of terpene enhancer treatment is to increase drug diffusivity, but also increase the drug partitioning into stratum corneum⁹. Oleic acid is an unsaturated fatty acid with a cis configuration, effect of oleic acid is associated with the linked structure owing to the cis bond.  It is stated that it reduces the order of intercellular lipid domain.  The lipid protein partition (LPP) theory has suggested that a penetration enhancer may act by one or more of the three main mechanisms.  (1) Disruption of the highly ordered structure of stratum corneum lipids. (2) Interaction with intercellular proteins and (3) Improved partitioning of drugs, co enhancers or co solvent into stratum corneum.  Infrared studies by Potts and Coworkers have revealed that the oleic acid acts by disruption of inter cellular Lipid domain¹⁰. More recent studies implied that oleic acid may coexist as pools in the ordered stratum corneum lipid bilayers. Pooling may provide a pathway of diminished resistance for drug transport with diffusion dependent on permeant’s nature.  Such defects in the lipoidal barrier of stratum corneum may explain the increased permeation of hydrophilic or even ionised molecule. Ethyl acetate is generally recognised as safe (GRAS) by FDA.  Ethyl acetate may be modifying the barrier in several ways simultaneously.  It has been suggested that ethyl acetate extracts lipid from stratum corneum which would lower the diffusional resistance of the skin.  In fact it is used as a delipidizing agent to remove sebum in clinical studies and shows ‘drying’ effect.  This effect may be responsible for enhancement the permeation enhancers were used to see the effect of the enhancers on the permeation profile of drugs under study.  Four penetration enhancers were used i.e. eucalyptus oil, menthol, oleic acid and ethyl acetate.  Thus it is seen from the results that eucalyptus oil has profound effect on penetration of glibenclamide through freshly excised rat abdominal skin. If the transdermal formulation is to be prepared then eucalyptus oil can be used as a good penetration enhancer in the formulation

 

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Received on 01.06.2009          Modified on 23.07.2009

Accepted on 26.08.2009         © RJPT All right reserved