What is Phenoxybenzamine used for?
Phenoxybenzamine is used to treat high blood pressure and heavy sweating due to a certain tumor of the adrenal glands (pheochromocytoma). Phenoxybenzamine belongs to a class of drugs known as alpha blockers. It works by relaxing and widening blood vessels so that blood can flow more easily.
How should I take Phenoxybenzamine?
Take this medication by mouth with or without food, usually 2 to 3 times daily or as directed by your doctor.
Dosage is based on your medical condition and response to therapy.
Use this medication regularly in order to get the most benefit from it. To help you remember, take it at the same times each day. It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick.
Do not suddenly stop taking this medication without consulting your doctor. Your condition may become worse when the drug is suddenly stopped. Your dose may need to be gradually decreased.
Inform your doctor if your condition worsens (e.g., your routine blood pressure readings increase).
How do I store Phenoxybenzamine?
Phenoxybenzamine is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Phenoxybenzamine in the bathroom or the freezer. There may be different brands of Phenoxybenzamine that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.
You should not flush Phenoxybenzamine down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.
Precautions & warnings
What should I know before using Phenoxybenzamine?
Before taking phenoxybenzamine, tell your doctor or pharmacist if you are allergic to it; or to other alpha blockers (e.g., phentolamine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: blood vessel disease (e.g., cerebral arteriosclerosis, coronary artery disease), heart disease (e.g., congestive heart failure), kidney disease, lung infections, certain eye problems (cataracts, glaucoma).
This drug may make you dizzy or drowsy. Alcohol or marijuana can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana.
Before having surgery (including cataract/glaucoma eye surgery), tell your doctor or dentist if you are taking or have ever taken this medication, and about all the other products you use (including prescription drugs, nonprescription drugs, and herbal products).
Caution is advised when using this drug in the elderly because they may be more sensitive to its effects, especially dizziness.
During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.
It is unknown if this drug passes into breast milk. Consult your doctor before breast-feeding.
Is it safe during pregnancy or breast-feeding?
There are no adequate studies in women for determining risk when using this Phenoxybenzamine during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking Phenoxybenzamine. Phenoxybenzamine is pregnancy risk category __ according to the US Food and Drug Administration (FDA).
FDA pregnancy risk category reference below:
- A=No risk,
- B=No risk in some studies,
- C=There may be some risk,
- D=Positive evidence of risk,
What side effects can occur from Phenoxybenzamine?
Stomach upset, nausea, stuffy nose, drowsiness, dizziness or decrease in pupil size may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.
To lower your risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if any of these unlikely but serious side effects occur: fast heartbeat, fainting, sexual problems in males (e.g., trouble ejaculating), weakness.
For males, in the very unlikely event that you have a painful or prolonged erection lasting 4 or more hours, stop using this drug and seek immediate medical attention, or permanent problems could occur.
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.
What drugs may interact with Phenoxybenzamine?
Some products that may interact with this drug are: drugs to treat erectile dysfunction-ED or pulmonary hypertension (e.g., sildenafil, tadalafil), epinephrine, other alpha blockers (e.g., prazosin), other drugs for high blood pressure (e.g., diuretics, ACE inhibitors, beta blockers).
Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana, drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).
Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.
Some products have ingredients that could raise your blood pressure. Tell your pharmacist what products you are using, and ask how to use them safely (especially cough-and-cold products, diet aids, or NSAIDs such as ibuprofen/naproxen).
Phenoxybenzamine may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.
Does food or alcohol interact with Phenoxybenzamine?
Phenoxybenzamine may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.
What health conditions may interact with Phenoxybenzamine?
Phenoxybenzamine may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.
The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this Phenoxybenzamine.
What is the dose of Phenoxybenzamine for an adult?
Usual Adult Dose for Pheochromocytoma
Initial dose: 10 mg orally twice daily
Maintenance dose: 20 to 40 mg orally 2 to 3 times daily until an optimal dosage (as judged by blood pressure control) is obtained.
The dosage should be adjusted to fit the needs of each patient. Increases in dosage should be made every other day, with careful observation of the patient after each increase. The dosage should be adjusted to a point where symptomatic relief and/or objective improvement are obtained, or until the side effects from blockade cannot be tolerated.
Caution is recommended in patients with marked cerebral or coronary arteriosclerosis or renal damage.
The adrenergic blocking effect may aggravate symptoms of respiratory infections.
Concomitant use of a beta-blocking agent may be necessary if tachycardia is excessive.
What is the dose of Phenoxybenzamine for a child?
The dosage has not been established in pediatric patients. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.
How is Phenoxybenzamine available?
Phenoxybenzamine is available in the following dosage forms and strengths:
- Oral capsule.
What should I do in case of an emergency or overdose?
In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.
What should I do if I miss a dose?
If you miss a dose of Phenoxybenzamine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Phenoxybenzamine HCL. https://www.webmd.com/drugs/2/drug-6758/phenoxybenzamine-oral/details. Accessed April 3, 2018.
Phenoxybenzamine Dosage. https://www.drugs.com/dosage/phenoxybenzamine.html. Accessed April 3, 2018.
Review Date: April 11, 2018 | Last Modified: April 11, 2018