Phenoxybenzamine is a prescription used to treat high blood pressure caused by an adrenal tumor called pheochromocytoma. Pheochromocytoma is usually a noncancerous tumor that develops in an adrenal gland. This type of tumor usually affects one of your two adrenal glands but it can also affect both. The adrenal glands are two small endocrine glands that sit above the kidneys. They help create and distribute important hormones including cortisol and adrenaline. Adrenal hormones help balance functions such as:
- Heart rate and blood pressure
- Blood sugar
- Stress and immune response
If you have this type of condition, the tumor releases hormones that cause either episodic or persistent high blood pressure. If left untreated, pheochromocytoma can result in severe or life-threatening damage to other body systems. The tumor can develop at any age but most people with pheochromocytoma are between the ages of 20 and 50. Signs and symptoms of pheochromocytoma may include:
- Heavy sweating
- High blood pressure
- Rapid heartbeat
- Paleness in the face
- Shortness of breath
- Anxiety or a sense of doom
- Weight loss
Phenoxybenzamine is in the class of drugs called alpha-blockers. This relaxes and widens blood vessels so that blood can flow more easily. This drug is a synthetic, benzamine alpha-adrenergic antagonist with anti-hypertensive and vasodilatory properties. Phenoxybenzamine blocks alpha receptors in certain parts of the body. Alpha receptors are present in the muscle that lines the walls of blood vessels. The muscle relaxes and the blood vessels widen when the receptors are blocked by this medication. The Food and Drug Administration (FDA) has already approved this prescription. This is supplied as a capsule for oral use. Each comes as a 10 mg capsule that contains Phenoxybenzamine as an active ingredient. It is a colorless, crystalline powder that is soluble in water, chloroform, and alcohol.
How does Phenoxybenzamine work?
A pheochromocytoma is a type of tumor of the adrenal gland that causes high blood pressure. It is because the tumor produces excessive amounts of the hormones adrenaline and noradrenaline. These hormones act on alpha-adrenergic receptors that are found on the walls of blood vessels that causes blood vessels to contract and narrow. Phenoxybenzamine works by opposing the action of the hormones produced by the tumor. It blocks the alpha receptors in the blood vessel walls. In that way, it stops adrenaline and noradrenaline from acting on them. This allows the blood vessels to relax and widen which lets the blood pass more easily through the blood vessels.
There is a slow onset of drug action that takes several hours which increases over several days after regular dosing. The effects of this medication persist for 3 to 4 days after discontinuation of the drug.
How to use Phenoxybenzamine?
The prescribed dosage is based on your medical condition and response to the treatment. You must take this medication exactly as it is given by your doctor. You should not take less or more often than the prescription. Your doctor may direct you to start at a lower dose and eventually increase it. Let your doctor know if your condition worsens or does not improve.
Phenoxybenzamine is to be taken by mouth usually 2 to 3 times a day or as directed by your doctor. You may take each dose with or without food. It is important to continue taking this even if you feel well. Do not suddenly stop taking Pindolol without the consent of your doctor. To help you remember, take it at the same time and in the same way each day. Swallow the capsule as a whole with a full glass of water. Do not break, chew, or crush it. Drink plenty of fluids while having this treatment. Doing so may lessen the risk of certain side effects. If you missed a dose, take it as soon as you remember it. If it is almost time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not double the dose to make up for the missed dose.
What are the side effects of Phenoxybenzamine?
Common side effects:
- Stomach upset
- Stuffy nose
- Lack of energy
- Light-headedness especially when getting up from a lying or sitting position
- Blurred vision
- Dryness of mouth
- A decrease in pupil size
- Tired feeling
- Trouble having an orgasm
Call your doctor right away if you have these serious side effects such as:
- Fast heartbeat
Get emergency medical help if you have any signs of an allergic reaction including:
- Trouble breathing
- Swelling of your face, lips, tongue, or throat
Warnings and Precautions
- Phenoxybenzamine may occasionally cause your blood pressure to drop when you move from a lying down or sitting position. This may make you dizzy and may rarely cause fainting. To avoid this, carefully move from lying down to sitting and try getting up slowly. If you feel dizzy, sit or lie down until the symptoms pass.
- This medicine may cause fatigue. Be careful when performing potentially dangerous activities such as driving. Do it until you know how this medicine affects you.
- This is not recommended for use in pregnancy unless considered essential by your doctor.
- If you are breastfeeding women, consult your doctor first before using this drug.
- Before using Phenoxybenzamine, tell your doctor if you have a medical history of blood vessel disease, heart disease, kidney disease, and lung infections.
- Limit alcoholic beverages while having this medication.
- Inform your doctor if you have current medications including herbal supplements and vitamins.
- Do not share this or any of your medications with others even if they have the same symptoms as yours.
- Use this with caution in elderly people, those with heart disease and failure, and those with a hereditary blood disease called porphyrias.
- This should not be used in people who have ever had a stroke and those who have had a heart attack in the last 3-4 weeks.
- You should not take a dose of this drug if you are allergic to it. Let your doctor know right away before using Phenoxybenzamine.