Comparative in vitro and in vivo Bioequivalence Analysis of some Brands of film coated Atorvastatin (a BCS Class II Compound) tablets marketed in Nigeria

The study is aimed at assessing the bioequivalence/quality of different brands of atorvastatin calcium 10mg tablets marketed in Nigeria. Physical parameters of the tablets, drug content, dissolution and pharmacokinetics data were assessed. The in vivo bioavailability study was carried out using a single dose randomized two period cross-over designs measuring the concentrations in plasma. Plasma samples before dosing and at various time intervals up to 48 hours after dosing were analysed using High- Performance Liquid Chromatography together with UV detector. Pharmacokinetics parameters (Cmax and AUC) were determined and subjected to statistical analysis. All brands complied with the official specification for uniformity of weight and disintegration time. Assay of atorvastatin tablets revealed that all samples contained atorvastatin calcium as their active ingredient between 91.4- 102.1% (w/w) of labelled potency. The dissolution profiles showed inter brand variability. Four brands attained 70% dissolution within 45 minutes, however, at 60 minutes, all the brands released over 80% of the drug. In vivo bioavailability study showed that three out of the four brands were bioequivalent to the innovator brand and can be substituted for each other in their prescription. Chemical equivalence does not indicate bioequivalence and one brand substituted on assumption of chemical equivalence with another brand may not give the desired onset of action and therapeutic effectiveness. Moreover, dissolution test might not be enough for ascertaining bioequivalence of atorvastatin and in vivo tests may be required to ensure the quality of marketed brands of atorvastatin.