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Amlodipine for Veterinary Use
by Barbara Forney, VMD
Amlodipine is a long-acting calcium channel blocker/vasodilator. The mechanism of action is through the inhibition of calcium entry into smooth muscle cells. Amlodipine has a relative degree of vascular selectivity.
Amlodipine is used primarily for systemic hypertension in cats and to a lesser extent for heart failure and hypertension in dogs. It may be combined with angiotensin converting enzyme (ACE) inhibitors, and beta- blockers. Amlodipine is well absorbed orally although the absorption and onset of action takes place over hours. Because of the slow onset of action, hypotension and loss of appetite are not commonly seen with this drug. The oral absorption of amlodipine is not affected by the presence of food. The half life is thought to be in the range of thirty hours in the dog. Although pharmacokinetic work has not been performed in the cat, in most instances, it is given as a once a day drug.
Amlodipine is considered a very successful first line treatment for systemic hypertension in the cat. Common causes of systemic hypertension in cats include kidney disease, hyperthyroidism, cardiomyopathy, and diabetes. Some clinicians prefer to use amlodipine with ACE-inhibitor drugs in cats with renal disease because of the potential for glomerular damage. Amlodipine therapy has been shown to decrease proteinuria in the majority (69%) of cats with chronic renal disease.
Amlodipine is used in the treatment of dogs with congestive heart failure, mitral valve regurgitation, and systemic hypertension due to chronic renal disease. Systemic arterial hypertension is a frequent complication of chronic renal disease in dogs. ACE inhibitor drugs are usually the drug of choice for hypertension in the dog, and amlodipine is added as needed.
- Side effects are not common in cats but may include depression, azotemia, hypokalemia, increased heart rate, and weight loss.
- Amlodipine has been shown to be feto-toxic in laboratory animals. It is not known if it enters maternal milk.
- Amlodipine is metabolized by the liver and should be used with caution animals with decreased liver function.
- Amlodipine depresses conduction velocity and impulse formation in cardiac muscle (negative inotropic). It should be used with caution in animals with heart failure or cardiac shock.
- Although no specific drug interactions are listed, concomitant use with other drugs that lower blood pressure (diuretics, beta-blockers, and vasodilators) could lead to clinically significant hypo-tension.
- Grapefruit juice may alter the bioavailability of amlodipine; the veterinary significance seems minimal.
- Overdose with calcium channel blockers generally result in profound hypo-tension and bradycardia.
- If recognized promptly, gut emptying protocols may be of value.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at www.exclusivelyequine.com
Wedgewood Pharmacy's compounded veterinary preparations are not intended for use in food and food-producing animals.