Amlodipine is well absorbed by the oral route with a mean oral bioavailability around 60%; the half-life of amlodipine is about 30 h to 50 h, and steady-state plasma concentrations are achieved after 7 to 8 days of daily dosing. In the blood it has high plasma protein binding of 97.5%. Its long half-life and high bioavailability are largely in part of its high pKa (8.6); it is ionized at physiological pH, and thus can strongly attract proteins. It is slowly metabolized in the liver by CYP3A4, with its amine group being oxidized and its side ester chain being hydrolyzed, resulting in an inactive pyridine metabolite. Renal elimination is the major route of excretion with about 60% of an administered dose recovered in urine, largely as inactive pyridine metabolites. However, renal impairment does not significantly influence amlodipine elimination. 20-25% of the drug is excreted in the faeces. History
Pfizers patent protection on Norvasc lasted until 2007; total patent expiration occurred later in 2007. A number of generic versions are available. In the United Kingdom, tablets of amlodipine from different suppliers may contain different salts. The strength of the tablets is expressed in terms of amlodipine base, i.e., without the salts. Tablets containing different salts are therefore considered interchangeable. Fixed-dose combination of amlodipine and perindopril, an angiotensin converting enzyme inhibitor are also available.The medical form comes as besylate, mesylate or maleate. Veterinary use
Amlodipine is most often used to treat systemic hypertension in cats and dogs.
In cats, it is the first line of treatment due to its efficacy and few side effects. Systemic hypertension in cats is usually secondary to another abnormality, such as chronic kidney disease, and so amlodipine is most often administered to cats with kidney disease. While amlodipine is used in dogs with systemic hypertension, it is not as efficacious. Amlodipine is also used to treat congestive heart failure due to mitral valve regurgitation in dogs. By decreasing resistance to forward flow in the systemic circulation it results in a decrease in regurgitant flow into the left atrium. Similarly, it can be used on dogs and cats with left-to-right shunting lesions such as ventricular septal defect to reduce the shunt. Side effects are rare in cats. In dogs, the primary side effect is gingival hyperplasia. References
External links

"Amlodipine". Drug Information Portal. U.S. National Library of Medicine. onog