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Alpha-adrenergic blocker (Smooth muscle relaxant)
Dogs, cats and horses
May Be Prescribed by Vets for:
Reduction of urinary sphincter tone, and treatment of hypertension due to pheochromocytoma.
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Phenoxybenzamine blocks the alpha adrenergic response to circulating epinephrine and norepinephrine. It has no effect on beta adrenergic receptors or on the parasympathetic nervous system. Phenoxybenzamine increases blood flow to the skin but does not affect cerebral or musculoskeletal blood flow. It has been shown to decrease both standing and supine blood pressure in humans.
Phenoxybenzamine is used in dogs and cats to reduce internal urethral sphincter tone. Although it is somewhat more effective in dogs than in cats, it is used in both species after a mechanical obstruction of the urethra has been relieved. It may also be used for urethral spasm secondary to bacterial urethritis. Phenoxybenzamine may be used concurrently with bethanechol .
Phenoxybenzamine is used to reduce blood pressure associated with pheochromocytoma. This rare neuroectodermal tumor of the chromaffin cells of the adrenal medulla most commonly occurs in older dogs but may also occur in cats. Approximately 50% of cases have episodic hypertension due to catecholamine secretion. These tumors are challenging to manage and treat due to the severity of the hypertension and cardiac arrhythmias. Phenoxybenzamine is used preoperatively in an attempt to regain control of blood pressure prior to surgery.
Phenoxybenzamine may be used to decrease urethral sphincter tone, in horses with an atonic bladder. It may be used with bethanacol. There are earlier reports of its use in the early stages of laminitis and for diarrhea. Phenoxybenzamine is an ARCI class 3 drug.
Common side-effects include:
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.
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This content is intended for counseling purposes only. This content is informational/educational and is not intended to treat or diagnose any disease or patient. No claims are made as to the safety or efficacy of mentioned preparations. The compounded medications featured in this content have been prescribed and/or administered by prescribers who work with Wedgewood Pharmacy. You are encouraged to speak with your prescriber as to the appropriate use of any medication. Wedgewood Pharmacy’s compounded veterinary preparations are not intended for use in food and food-producing animals. All product and company names are trademarks™ or registered® trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.