Emtricitabine

An HPLC method has been developed for simultaneous estimation of tenofovir disoproxil and emtricitabine in bulk and in their tablet dosage form. Separation and analysis of both drugs was achieved on Supelco C18 (250 x 4.6 mm; 5 µm particle size) analytical column with temperature set at 25˚C. The best chromatographic condition was found as an isocratic mobile phase consisting of 0.2 M ammonium acetate (pH 4.5) and methanol in a ratio of 65: 35 (% v/v) at a flow rate of 1.2 ml/min for 6 minutes. The retention of emtricitabine and tenofovir disoproxil was found to be 3.020 min and 4.264 min, respectively. The method was validated according to the International Conference on Harmonization guidelines and various validation parameters (system suitability, selectivity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness) were determined. The results of validation parameters are satisfactory. Applicability of the developed and validated HPLC method was checked in tablet dosage form.

The main objective of the study is to formulate emtricitabine, a nucleoside reverse transcriptase inhibitor used in the treatment of Human Immuno deficiency Virus (HIV) infections as a niosomal formulation to improve the Central Nervous System (CNS) penetration of the drug and evaluate its CNS penetration using in vitro blood-brain barrier penetration study using immobilized artificial membrane phosphatidylcholine column chromatography. Emtricitabine encapsulated niosomes were prepared by thin layer evaporation (TLE)-paddle stirring method with Span 60 as main surfactant. Cholesterol (CHL), Solulan C24 (SOL) and N-palmitoyl glucosamine (NPG) were also included in the niosomal formulations. The ratio of Span 60:CHL:SOL:NPG was 50:40:10:10 with total concentration of components as 38 mM.  The hydration temperature was maintained at 65 0C. Sonication method was employed for size reduction of the niosomes. The formulation was evaluated for CNS penetration by in vitro blood-brain barrier penetration study using immobilized artificial membrane phosphatidylcholine column chromatography. The Scanning electron microscopic images showed good formation of the niosomal vesicles. The mean particle size and encapsulation efficiency were found to be 154±4 nm and 64.45±1.14% respectively. In vitro blood-brain barrier (BBB) penetration of emtricitabine from drug loaded NPG niosomes using immobilized artificial membrane phosphatidylcholine column chromatography showed an improved CNS penetration of the drug with (kIAM/MW4) X 1010 values of 2.79±0.05 at pH 5.5 and 8.48±0.18 at pH 7.0. The results showed an increased CNS penetration when the drug was encapsulated in niosomes and may be considered as a potential alternative to improve brain targeting of emtricitabine and thus minimize HIV Associated Neurocognitive Disorders (HAND).

An accurate, precise and reproducible high performance liquid chromatographic method was developed for quantitative estimation of emtricitabine, efavirenz and tenofovir disoproxil fumarate simultaneously in tablet dosage forms. Separation of the drugs was achieved within 15.0 min on a Xterra RP-18 column (150 x 4.6 mm; 5µ) by gradient elution using mixtures of ammonium acetate buffer and acetonitrile as the mobile phase. The analytes in the eluate were monitored at 260 nm. The retention times obtained for emtricitabine, efavirenz and tenofovir disoproxil fumarate were 4.611, 9.098 and 7.512 min respectively. The calibration curves were linear over the range of 20.11-60.33 µg/mL for emtricitabine, 60.28-180.45 µg/mL for efavirenz and 30.13-90.18 µg/mL for tenofovir disoproxil fumarate. The performance of the method was validated according to ICH guidelines. The method was found to be suitable for accurate determination of these drugs in tablet dosage forms without any interference from excipients or endogenous substances.