Simultaneous Quantitation of Captopril and NSAID’s in API, Dosage Formulations and Human Serum by RP-HPLC Najma Sultana, a M. Saeed Arayne b and Safila Naveed c, * a Research Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Faculty of Pharmacy University of Karachi, Karachi-75270, Pakistan b Department of Chemistry, University of Karachi, Pakistan c Faculty of Pharmacy, Hamdard University, Karachi, Pakistan An accurate, sensitive and least time consuming reverse phase high performance liquid chromato- graphic (RP-HPLC) method for the estimation of captopril in the presence of non steroidal anti-inflamma- tory drugs in formulation and human serum has been developed and validated. Chromatographic separa- tion was conducted on prepacked Purospher star C18 (5 mm, 25 ´ 0.46 cm) column at room temperature using methanol:water (80:20 v/v) as a mobile phase, pH adjusted at 2.8 with o-phosphoric acid and at a flow rate of 1.0 mL min -1 , while UV detection was performed at 227 nm. The limit of detection and quanti- fication for captopril were 1 and 0.35 ng mL -1 , while that for (NSAID’s) i.e. flurbiprofen, ibuprofen, diclofenac sodium and mefenamic acid LOD were 0.2, 1, 2 and 0.4 ng mL -1 respectively and LOQ were 0.9, 2.9, 8 and 1 ng mL -1 Analytical recovery was > 98.1%. The method used for the quantitative analysis of commonly administered non steroidal anti-inflammatory drugs (NSAID’s) i.e. ibuprofen, flurbiprofen, diclofenac sodium and mefenamic acid alone or in combination with captopril from API (active pharma- ceutical ingredients), dosage formulations and in human serum. The established method is rapid (RT < 12 min), accurate (recovery > 98.1%), selective (no interference of excepients and other commonly used drugs and food) and sensitive (LOQ 3.5 ng mL -1 ) and reproducible (SD ± 0.003). Keywords: Captopril; Ibuprofen; Flurbiprofen; Diclofenac sodium; Mefenamic acid; RP-HPLC. INTRODUCTION Captopril (Fig. 1) is 1-[(2S)-3-mercapto-2-methyl-1- oxo-proptonyl]-L-proline, 1 the first orally active and spe- cific inhibitor of angiotensin-converting enzyme. It blocks conversion of angiotensin I to angiotensin II by inhibiting the angiotensin converting enzyme and inactivates brady- kinin, a potent vasodilator. The hypotensive activity of captopril probably results both from inhibitory action on renin-angiotensin system and simulating action on kal- likerin-kinin system. 2 At present, most commonly prescribed NSAID’s ibuprofen, flurbiprofen, diclofenac sodium, and mefenamic acid were used in these studies. These belong to arylal- kanoic acids (Fig. 2). 3-5 They are polyvalent drugs, able to modulate more than one molecular or cellular events thought to be concerned in inflammation. 6,7 One of the study showed that captopril and ibuprofen had opposing effects on sodium and water handling by the kidney. 8 A case of acute renal failure was also found by the co-administration of captopril and NSAID’s, 9 and nephro- toxicity had also been associated with concomitant ACE- 62 Journal of the Chinese Chemical Society, 2010, 57, 62-67 * Corresponding author. E-mail:safila117@yahoo.com; safila117@gmail.com Fig. 1. Captopril. Fig. 2. Arylalkanoic.