Quantitative analysis of tenofovir by titrimetric, extractive ion-pair spectophotometric and charge- transfer complexation methods

Purpose: Tenofovir disoproxil is an antiretroviral agent belonging to the class of nucleoside reversetranscriptase inhibitors (NRTI's) used in the management of HIV infection in adults. This study is aimed at developing and validating four simple, sensitive and cost-effective analytical methods for ascertaining the drug's quality. Methods: Tenofovir disoproxil forms a complex of 1:1 molar ratio with fumaric acid that was employed in its aqueous titration with sodium hydroxide. Non-aqueous titration was also employed for its determination. Extractive ion-pair spectrophotometric technique using methyl orange was similarly employed to evaluate quantitatively the amount of tenofovir in the formulation. The drug was further assayed by forming a charge-transfer complex with chloranilic acid and the coloured complex assayed spectrophotometrically. Results: Recovery experiments carried out by the proposed methods showed that aqueous titration gave mean recovery of 97.7 % while non-aqueous titration gave 97.5 % recovery. The technique of extractive ion-pair spectrophotometry similarly gave 98.7 % mean recovery while charge transfer spectrophotometry gave 99.6 % for the same parameter. Conclusion: These results show that the proposed methods are accurate, precise and sensitive. In addition to being simple and cost-effective, they can conveniently be used for the assay of tenofovir which has yet no official assay procedure. This investigation, therefore, contributes to the knowledge on the development of assay techniques for a drug that is already extensively distributed in the market. © Pharmacotherapy Group.