EXTRACTIVE SPECTROPHOTOMETRIC METHODS FOR THE ASSAY OF OSELTAMIVIR PHOSPHATE, FAMCICLOVIR AND ACYCLOVIR IN PURE AND DOSAGE FORMS

For the determination of oseltamivir phosphate (OSP), acyclovir (ACL), and famciclovir (FMV) medicines in pure form and their formulations, quick, accurate, and simple spectrophotometric procedures have been established. The procedures were relied on the formation of ion-pair complexes between the drugs and anionic dyes (OSP with bromothymol blue (BTB), ACL with methyl red (MTR) and FMV with methyl orange (MTO)) in an acidic medium, separately. The yellow OSP-bromothymol blue complex, orange ACL-methyl red complex and orange-yellow FMV-methyl orange complex formed were quantitatively extracted with chloroform and their absorbance measured at 416, 416 and 488 nm wavelengths, respectively. The limits of detection and quantification were found to be 0.5, 1.5, 1.0 µg mL-1 and 1.7, 5.0 and 3.3 µg mL-1 for the OSP, ACL and FMV, respectively. The linearity was established from 1-5, 2-12 and 5-14 µg mL-1 for OSP, ACL and FMV, respectively. R2 (regression coefficient) values were above 0.996 for all the three drugs. Recovery (accuracy) results were found within 98.0 % to 102 %. The developed methods comply with the ICH guidelines. The developed methods were successfully used to measure OSP, ACL and FMV in both their pure and in formulation forms.