Int. Res J Pharm. App Sci., 2013; 3(5):120-126 ISSN: 2277-4149 Bhandary et al., 2013 120 International Research Journal of Pharmaceutical and Applied Sciences (IRJPAS) Available online at www.irjpas.com Int. Res J Pharm. App Sci., 2013; 3(5):120-126 NON-COMPARTMENTAL PHARMACOKINETICS MODELING OF AMLODIPINE IN RATS Ashesh Bhandary 1, 2 , Arpana Pradhan Bhandary 1 , Gulam Muhammad Khan 2 and Bijay Aryal 3 * . 1 Research and Development Department, Time Pharmaceuticals P.Ltd, Mukundapur, Nawalparasi, Nepal. 2 Department of Pharmacy, School of Health and Allied Sciences, Pokhara University, Kaski, Nepal. 3 Department of Clinical Pharmacology, Chitwan Medical College P.Ltd, Bharatpur-10, Chitwan, Nepal. Corresponding Author: : Dr.Bijay Aryal, PhD, Email: aryal.bijay@cmc.edu.np Abstract: In the present study, we did the non –compartmental pharmacokinetics study of amlodipine using high performance liquid chromatography with ultraviolet detector (HPLC-UV) in wistar rats. Rats were allocated to two groups; intravenous group (IV study n=6) and oral group (PO study n=6).In both groups, surgical procedures were carried out under Ketamine HCL (40 mg/kg) and Diazepam (1.5mg/kg) general anesthesia (intramuscular injection).The blood samples were collected at different time interval and were analyzed using HPLC-UV system. Results showed that Amlodipine had a short terminal half-life with relatively high distribution volumes during the steady and terminal phases, and with low plasma clearance. Furthermore, the availability ratio of amlodipine through the intravenous route was higher than that through the oral route, indicating that first pass metabolism and hepatic blood flow are important factor of drug elimination of amlodipine. Bioavailability was estimated to be 78.60 ± 21.33% based on the AUCinf ratios of oral and intravenous administration. Keywords: Wistar rats, amlodipine, pharmacokinetics parameters and bioavailability. Introduction Rat is an attractive model for many biomedical researches. Availability of various breeds and knockouts that emulate disease states or altered metabolism advocate its importance in pharmacological or pharmacokinetic studies. Being small in size, it requires relatively small quantity of expensive new chemical entities to conduct pharmacokinetic studies 1, 2 . Various methods are available to collect blood from a rat for pharmacokinetic studies. Among these, a timed-sacrifice or tail-bleed methods are widely used. However, the timed- Sacrifice generates inevitable inter-animal variation, whereas tail-bleed limits to fewer samples with low blood volume 3, 4 . Big vessels cannulation generates multiple samples with precision and ease has been successfully applied in rat 5 . The surgical techniques allow low stressed sample collection from a small animal. Direct drug injection to big vessels established pharmacokinetics studies with high precision and accuracy 6 . Amlodipine is a dihydropyridine calcium antagonist (calcium ion antagonist or slow-channel blocker) that inhibits the movement of calcium ions into vascular smooth muscle cells and cardiac muscle cells 7, 8 . Experimental data suggest amlodipine binds to both dihydropyridine and nondihydropyridine binding sites. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels 9 .Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells. Negative inotropic effects, or decreased heart muscle contractility, can be detected in vitro, but such effects have not been seen in intact animals at therapeutic doses. Serum calcium concentration is not affected by amlodipine 10 . Within the physiologic pH range, amlodipine is an ionized compound (pKa = 8.6), and its interaction with the calcium channel receptor is characterized by a gradual rate of association and dissociation with the receptor binding site, resulting in a gradual onset of effect 11, 12 .In the present study, we did the non –compartmental pharmacokinetics study of amlodipine using high performance liquid chromatography with ultraviolet detector (HPLC-UV) in wistar rats. Materials and methods After getting ethical approval from thesis committee of Department of Pharmacy, School of Health and Allied Sciences, Pokhara University on May 14, 2013, the research work has been conducted at Research and Development Department of Time Pharmaceuticals P.Ltd. Chemicals and Reagents Amlodipine (purity 99.96%) and Hydrochlorothiazide (Purity 100.78%) has been received as gift samples from Time Pharmaceuticals P.Ltd. Acetronitrile, Potassium dihydrogen phosphate, Orthophosphoric acid were pursed from Merck, Darmstadt, Germany. Double distilled water was obtained from Fisher Scientific, United Kingdom and all other chemicals used were of HPLC grade. Apparatus and Chromatographic Conditions The HPLC-UV system used was an Agilent 1260 series. System control and data analysis were carried out using Agilent HPLC software (Agilent Chemstation V.B.30.01, Germany). HPLC columns Phenomenex ® C18 (phenomenex, CA, USA), 250 mm × 4.6 mm, 5 μm particle size and guard column (C18, 4.0 X 2.0mm, Shimadazu, Research Article