A simple, sensitive and reproducible method was developed and validated for the simultaneous estimation of diethylcarbamazine and levocetirizine in its tablet formulation by reverse phase high performance liquid chromatography using Waters1515 HPLC with UV detector at the max of 224 nm, using Princeton Sphere-100 C18 (2504. 30 g/ml 0.1 to 1 g/ml for diethylcarbamazine and levocetirizine, respectively. Hence this method can be applied for quantification of different formulations containing diethylcarbamazine and levocetirizine simultaneously. Keywords: C18 column, diethylcarbamazine, levocetirizine, RP-HPLC, validation Diethylcarbamazine (DEC) is a piperazine anthelmintic agent indicated for the treatment of individual patients with lymphatic filariasis, tropical pulmonary eosinophilia and loiasis. The chemical name of the drug is N,N-diethyl-4-methylpiperazine-1-carboxamide citrate. It acts by inhibiting arachidonic acid metabolism and it is a polar compound. Levocetirizine (LEVC) is a third generation non-sedative antihistamine developed from second-generation antihistamine; cetirizine. Chemically LEVC is active enantiomer of cetirizine. The chemical name is 2-(2-(4-((R)-(4-chlorophenyl)-phenyl-methyl) piperazin-1-yl) ethoxy) acetic acid dihydrochloride. It is more effective with fewer side effects than second generation drugs. It works by blocking histamine receptors and it is polar compound in nature. Both drugs have good pharmacological actions. Many formulations are marketed individually or combination with other drugs. UV/Vis spectrophotometric methods[3C5], high performance liquid chromatographic (HPLC) methods[6C9], liquid chromatography-tandem mass spectroscopic (LC-MS/MS) method and gas chromatographic (GC) method are available for estimation of DEC and LEVC in formulations individually or in combination with other compounds or in plasma samples. DEC and LEVC combined formulation is recently available marketed product. Literature survey showed that no HPLC method is available for estimation of these drugs simultaneously. The present study aims in developing RP-HPLC method for simultaneous estimation of these compounds in formulations. All the chemicals buy 4311-88-0 used were of HPLC grade. Potassium dihydrogen orthophosphate was obtained from Qualigens fine chemicals, orthophosphoric acid and acetonitrile were obtained from Rankem Fine Chemicals, Mumbai, India. All the drugs DEC citrate, LEVC dihydrochloride and losartan potassium (IS) were purchased from Sigma Aldrich chemicals, Bangalore, India. Tablets of Levodec (equivalent to 150 mg of DEC and 2.5 mg of LEVC, Reign (India) Formulations Pvt. Ltd, Mettupalayam, India) were purchased from a local pharmacy. The ultra pure water used was collected from Millipore system. The method development was performed with Waters 1515 HPLC system (Dual max 2487 UV detector), Rheodyne 7725i injector with 20-l loop and the output signal was monitored and integrated using Breeze software (3.30 version), Shimadzu UV 1700 spectrophotometer for optimizing the wave length. Sartorious digital balance, Systronics pH meter and ultra sonicator were used. Shimadzu Prominence HPLC (LC-20AT pump, SPD-20A detector) was used for determining the ruggedness of the method. Mobile phase used was 20 M potassium dihydrogen orthophosphate buffer adjusted to pH 3.2 and acetonitrile with 50:50% v/v, it was filtered and degassed by ultra sonication. Standard solutions of DEC, LEVC and IS were prepared separately at a concentration of 1 1 mg/ml and further dilutions were made to prepare working standard solutions used for validation studies. IS was maintained in each standard solution at a concentration of 50 g/ml prepared buy 4311-88-0 from 1 mg/ml. All the dilutions were made with mobile phase. Twenty tablets were powdered and average weight equivalent to one tablet was weighed and dissolved by adding mobile phase and sonicated for 30 min. It was filtered buy 4311-88-0 to remove the matrix by using Whatman filter paper of pore size 1 and made up the volume UPK1B to 100 ml with mobile phase (solution A). From solution A, 1 ml was taken and made up the volume to 10 ml with mobile phase (solution B). From solution B, 1 ml was taken and 0.5 ml of 1 1 mg/ml of IS stock solution were mixed and made up the volume to 10 ml with mobile phase. Separation of compounds was carried out by using reverse phase columns (Princeton SPHERE 100 C18, 2504.6 mm id, 5, Hibar? C18 2504.6 mm id, 5) and Princeton SPHER-100 C18 (2504.6mm 5 ), was selected as the stationary phase, with a flow rate maintained at 1 ml/min with isocratic solvent pumping system. The analysis was done at ambient temperature (~20). 20 l of sample was injected.