A New Analytical Q-Absorbance Ratio Method Development and Validation for Simultaneous Estimation of Lamivudine and Isoniazid

A new UV spectrophotometric absorption ratio method was developed and validated for the simultaneous estimation of lamivudine and isoniazid. The method involved Q-absorption ratio analysis using two wavelengths, with one being the of lamivudine (272？nm, ) and the other being the isoabsorptive point of both drugs (246？nm, ). Beer’s law was obeyed in the concentration range between 5 and 30？μg/mL for both lamivudine and isoniazid. The results of analysis have been validated statistically and by recovery studies as per ICH guidelines. The accuracy ranged between 99.65 and 101.91% and Sandell’s sensitivity ranged between 0.0229 and 0.0347？μg/cm2. The method was found to be simple, precise, reproducible, rapid, and economical. Hence, it could be used in the analysis of laboratory samples and marketed formulations containing these two drugs in the future. 1. Introduction A recent WHO report on tuberculosis (TB) in 2012 has shown that there were an estimated 8.7 million incident cases of TB in 2011 (13% coinfected with HIV). There were also 1.4 million deaths from TB, 990,000 deaths among HIV-negative individuals and 430,000 among people who were HIV-positive [1]. Many TB carriers who are infected with HIV are 30 to 50 times more likely to develop active TB than those without HIV [2]. HIV infected individuals are not only at a greater risk for acquiring TB but also reactivation of latent TB infection is greatly increased due to the fact that the very cells that hold the latent TB in check (the CD4+ T lymphocytes) are precisely the cells that are rendered dysfunctional in HIV-infected individuals. There are evidences to believe that the main factor for the resurgence of TB has been the human immunodeficiency virus (HIV) [3]. Lamivudine (LAM), a leading antiretroviral drug, also known as 3TC, is chemically 2(1H)-pyrimidinone, 4-amino-1-[2-(hydroxymethyl)-1, 3-oxathiolan-5-yl]-, (2R-cis) (Figure 1) with molecular formula C8H11N3O3S and molecular weight 229.26 [4]. This deoxycytidine analogue is phosphorylated intracellularly and inhibits HIV reverse transcriptase as well as hepatitis B virus DNA polymerase. Most human DNA polymerases are not affected and systemic toxicity of 3TC is low [5]. Isoniazid (INH), a first line antitubercular, is chemically 4-pyridinecarboxylic acid hydrazide or isonicotinic acid hydrazide (Figure 2), having molecular formula C6H7N3O and molecular weight 137.14 [4]. It acts by inhibiting the synthesis of mycolic acids which get attached to arabinogalactan to form part of mycobacterial cell wall. It is an essential component of all