Abstract
Four sensitive and rapid methods for the determination of stavudine (STV) in bulk drug and in dosage forms were developed and optimized. In titrimetry, aqueous solution of STV was treated with a known excess of bromate-bromide in HCl medium followed by estimation of unreacted bromine by iodometric back titration. Spectrophotometric methods involve the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange, indigocarmine or thymol blue followed by measurement of absorbance at 520 nm (method A), 610 nm (method B) or 550 nm (method C). In all the methods, the amount of bromate reacted corresponds to the amount of STV. Calculations in titrimetry were based on a 1:0.666 (STV:KBrO3) stoichiometry and the method was found to be applicable over 3.5-10 mg range. A linear increase in absorbance with concentration of STV was observed in the spectrophotometric methods, and the Beer's law was obeyed over the concentration ranges 0.125-1.75, 1-10 and 1-9.0 microg mL-1 STV for method A, method B and method C, respectively. The methods when applied to the determination of STV in tablets and capsules were found to give satisfactory results.
Highlights
Stavudine (STV), chemically known as 21-31-didehydro21-31-dideoxythymidine (Fig. 1), is a nucleoside analog reverse transcriptase inhibitor (NARTI) active against HIV (The Merck Index 1996)
The drug is official in United States of Pharmacopoeia (The United States Pharmacopoeia 2006). which describes high performance liquid chromatography as assay procedures for bulk drug and tablets, respectively
A number of methods based on high performance liquid chromatography (Bazy et al 2005, Verweij-van Wissen et al 2005, Contreras et al 2004), liquid chromatography-tandem mass spectrometry (Compain et al 2005, Huang et al 2004, Raices et al 2003, Fan et al 2002, Wiesner et al 2002), micellar electrokinetic chromatography (Fan and Stewart 2002), radio immuno assay (Tran et al 2003) and electrophoresis (Pereira et al 2005) are known for the quantitative determination of STV in biological matrices such as blood plasma, blood serum and human cells
Summary
Stavudine (STV), chemically known as 21-31-didehydro21-31-dideoxythymidine (Fig. 1), is a nucleoside analog reverse transcriptase inhibitor (NARTI) active against HIV (The Merck Index 1996). It is the fourth antiretroviral drug in the market and is used in the treatment of HIV infection. Three procedures (Sarma et al 2002a) have been reported for the assay of STV in pharmaceuticals using KMnO4-Fast green FCF, permanganate/periodateMBTH and iron(III)chloride-ferricyanide as reagents. A method based on oxidative-coupling reaction (Sankar et al 2002b) involving the use of iron (III)MBTH is found in the literature. These methods suffer from one or the other disadvantage like poor sensitivity, heating or extraction step and/or use of expensive chemical/organic solvent. The methods on applying to tablets and capsules yielded satisfactory results and were comparable with those of a reference method
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