Evaluation and comparison of in-vitro dissolution profiles for different brands of amoxicillin capsules

Background: Amoxicillin is an oral semi-synthetic, b-lactam antibiotic used to treat bacterial infections caused by susceptible micro organisms. It is usually prepared in capsule, tablet and powder for oral suspension form. Solid dosage forms for oral administration pose bioavailability problems related to the absorption process. The World Health Organization (WHO) has promoted the use of generic brands in order to make the cost of medicines affordable. Generic substitution could be considered when a generic copy of a reference drug contains identical amounts of the same active ingredient in the same dose formulation and route of administration. However, the presences of generic products those are not interchangeable with that of the innovator and/or with each others have been reported.
Objective: To evaluate and compare the in-vitro dissolution profiles of different generic brands of amoxicillin capsules with the innovator that are available in Ethiopian market.
Methods: Dissolution profiles for nine brands of amoxicillin capsules contained amoxicillin 500 mg which are available in Ethiopian market were determined using a method from the United States Pharmacopoeia (USP, 2009). The obtained dissolution profile data of the eight brands were evaluated and compared with the innovator brand (Amoxil^TM) using two different statistical methods: the fit factors (f1 & f2) and the dissolution efficiency (D.E.) model. Most generic brands of amoxicillin capsules (62.5% of the tested brands) are not interchangeable with the innovator brand.
Results: The calculated f1 factor for Brand A and Brand G are 10.1 and 1.1 respectively. However, for the rest six brands the f1 factors are greater than 15. The f2 factor for Brand G is 74.1 and for Brand A is 48.5 which is near to 50. Similarly, the f2 factors for the six brands are less than 50 which support the result of the f1 factors for the dissimilarity of these brands with the innovator brand. The mean dissolution efficiencies as well as the 95% confidence intervals are within ±10% only for two brands, Brand F and Brand G.
Conclusion: Most generic brands of amoxicillin capsules (62.5%) are not interchangeable with the innovator brand (Amoxil^TM).