References: Tripathi KD, Essentials of Medical Pharmacology,Seventh Edition:2013, Jaypee Brothers medical Publishers (P) Ltd, Nwe Delhi. Pharmacology and pharmacotherapeutics by R.S Satoskar,21st edition,2012,popular prakashan . Rang H.P, Dale M.M, Ritter.J , Flower.R ,” Rang & Dales Pharmacology, Sixth Edition 2010. Published By : Churchill Livingstone.