INTRODUCTION Simvastatin, a 3-hydroxy-3-methyl glutaryl co-enzyme A reductase inhibitor, is chemically designated as [(1S, 3R, 7R, 8S, 8aR)] -8-[2-[2R, 4R) -4-hydroxy-6-oxo-oxan-2-2yl [-3, 7-dimethyl - 1, 2, 3, 7, 8, 8a–hexahydronaphthalen-1-yl]2, 2- dimethyl butanoate 1 . It belongs to a class of drug known as statins that exert their effect by reduction of LDL levels through a mevalonic acid-like moiety that competitively inhibits HMG-CoA reductase. Simvastatin is well tolerated and quite effective in the treatment of dyslipidemia and prevention of ischemic heart disease. The role of simvastatin in reducing mortality and incidence of coronary events has been well documented 2 . Hypercholesterolemic individuals treated with simvastatin showed a reduction in the levels of pro- inflammatory cytokines 3 . Simvastatin has been found to reduce inflammation, decrease leukocyte Biomedical & Pharmacology Journal Vol. 5(1), 105-109 (2012) Novel Extractive Ultraviolet Spectrophotometric Determination of Serum Simvastatin Concentration NDUBUISI N. NWOBODO¹*, PAUL O. OKONKWO² and NICHOLAS C. OBITTE³ ¹Department of Pharmacology & Therapeutics, Ebonyi State University (Abakaliki). ²Department of Pharmacology & Therapeutics, University of Nigeria Teaching Hospital, Ituku (Ozalla). ³Department of Pharmaceutical Chemistry, University of Nigeria (Nsukka). (Received: April 08, 2012; Accepted: May 13, 2012) ABSTRACT This study is aimed at developing and describing a simple, precise, reliable and novel spectrophotometric technique for the determination of serial serum concentration of simvastatin in vivo. Double beam ultraviolet spectrophotometer is employed to determine absorbance readings for corresponding serial concentration of standard stock solution. The absorbance of test sample obtained from serum is then determined and the concentration of test sample deduced from the calibration curve. The calibration curve of simvastatin is found to be linear within Beer-Lambert’s law limits at concentration range of 0.1-20μg/ml. This is represented mathematically in the linear regression equation, y = 0.0174x-0.016. The maximal absorbance wavelength (λmax) is shown to be 280nm. The spectrophotometric technique described in this study has been shown to be quite appropriate, accurate and highly sensitive in detecting very low serum concentrations of simvastatin in vivo; and can be routinely employed clinically for therapeutic drug monitoring. Key words: Absorbance, Concentration, Simvastatin, Therapeutic drug monitoring, Ultraviolet spectrophotometer. rolling and adherence in apolipoprotein-E deficient mice 4,5 . There is need for therapeutic drug monitoring in the course of simvastatin therapy. There are various methods reported in the literature for determination of simvastatin such as high performance liquid chromatography with ultraviolet detection 6 , liquid chromatography coupled with tandem mass spectroscopy 7 and ultraviolet spectrophotometry 8 . Other analytical methods have also been reported for determination of simvastatin 9-11 . However, these techniques are mostly employed in the determination of simvastatin in bulk and pharmaceutical dosage forms. Those that can be employed in the determination of simvastatin in serum or biological fluids, are not suitable for routine analysis because they require sophisticated instruments that are not readily available, involve numerous steps and tedious processes resulting to insufficient sensitivity. The review of literature revealed that no method has been reported for determination of simvastatin in