The Canadian federal circuit court has upheld the validity of a innovator Pfizer ‘s patent CA1321393 (Expiry: August, 2010)- which covers a process for preparing the besylate salt of amlodipine characterised by the steps of reacting amlodipine base with a solution of benzenesulphonic acid or its ammonium salt in an inert solvent and recovering the besylate salt of amlodipine.
Pharmascience may appeal the decision to the Federal Court of Appeal of Canada. In a ruling Judge Roger T. Hughes of the Canadian Federal Court stopped Canada’s Minister of Health from approving Pharmascience s generic copy of Norvasc (Amlodipine) until Pfizer’s patent expires The invalidity challenges to this patent in Canada by other generic manufacturers are still pending. The decision by Canadian Federal Court prevents Pharmascience from launching a generic version of the drug until the Canadian patent expires in 2010. Norvasc sales plunged 52 per cent to $513 million in the quarter.
Amlodipine (3-ethyl-5-methyl-2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5- pyridinedicarboxylate) is a long-acting calcium channel blocker (dihydropyridine) used as an anti-hypertensive and in the treatment of angina. As other calcium channel blockers, amlodipine acts by relaxing the smooth muscle in the arterial wall, decreasing peripheral resistance and hence reducing blood pressure; in angina it increases blood flow to the heart muscle.
Amlodipine is marketed as Norvasc® in North America and as Istin® in the United Kingdom by Pfize. The patent on Amlodipine has alredy expired in USA in 2007 and number of generic version of this drug are availabe in U.S market
