Prazosin

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Apr 17, 2024

Warnings

Prazosin (Minipress) Risks, Warnings, and Complications

Prazosin can cause or worsen serious health problems in some people. Talk to your doctor or pharmacist about other treatment options for your condition if you are at an increased risk of complications from this medication. Some of the risks of taking prazosin include:

ORTHOSTATIC HYPOTENSION: Taking Minipress (prazosin) and other alpha-blocker drugs can cause orthostatic hypotension (low blood pressure when going from a lying or sitting position to standing). This can result in a sudden loss of consciousness. Sometimes, fainting (syncope) is accompanied by severe tachycardia (rapid heart rate of up to 120-160 beats per minute). The risk of fainting is higher after the first dose, after a rapid dose increase, and after the addition of another antihypertensive drug in patients taking high doses of prazosin. Taking certain medications called PDE5 inhibitors, which are used to treat erectile dysfunction (ED), can have an additive blood pressure-lowering effect and cause orthostatic hypotension.
Your doctor will start you on a low dose of prazosin and gradually increase the dose. They may ask you to take the first dose in the evening before bedtime. Take the medicine at the dose prescribed. Make sure you go slowly from a seated or lying position to standing. Seek medical attention if symptomatic hypotension (severe dizziness) occurs after taking prazosin. Your doctor may lower your dose.
INTRAOPERATIVE EYE PROBLEMS: Post-marketing experience has shown that taking Minipress (prazosin) can increase the risk of intraoperative floppy iris syndrome, a complication that can occur during cataract surgery. Before any surgical procedure on your eyes, tell your surgeon you are on an alpha-blocker drug. They may ask you to temporarily discontinue prazosin before the surgery and/or modify their surgical technique.
PRIAPISM: Prazosin and other alpha-blockers can cause a condition called priapism, in which a painful or prolonged erection lasts for several hours. This is an emergency and can result in permanent damage to the penis. Seek immediate medical attention if you develop a painful erection that does not go away.

Precautions Before Starting Prazosin (Minipress)

Tell your doctor if you have ever had allergic reactions to prazosin, any of the active or inactive ingredients in prazosin capsules, other alpha-blocker drugs, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, nutritional supplements, and herbal products. This can help avoid possible drug interactions.

Give your doctor a complete medical history. Alpha receptor inhibitor therapy with prazosin may not be safe for people with certain medical problems such as narcolepsy (excessive sleepiness), liver disease, heart disease, or prostate cancer. Your doctor will weigh the potential benefits versus risks before prescribing prazosin to you.

This medication may not be safe for pregnant women. Tell your doctor if you are pregnant, could be pregnant, are planning a pregnancy, or are breast-feeding.

Precautions During Use of Prazosin (Minipress)

Keep all your medical and lab appointments while taking Minipress (prazosin). Your doctor may adjust your dose based on your response.

Prazosin can cause drowsiness, dizziness, blurred vision, and reduced mental alertness. Be careful when driving and operating machinery until you know how this medicine affects you.

You may feel dizzy or lightheaded after taking Minipress (prazosin), especially when going from a lying or sitting position to standing. Do not get out of bed too fast. Place your feet on the floor for a short while before you stand up. If you feel dizzy, sit down for a few minutes. These symptoms are more likely to occur after the first dose and after your dose is increased. They are also more likely after drinking alcohol, prolonged standing, exercising, and in hot weather. Avoid drinking alcohol while on prazosin. Tell your doctor if the symptoms continue.

Tell all your health care providers that you are on prazosin before any surgery, including eye surgery and dental procedures.

Prazosin (Minipress) Drug Interactions

Certain other drugs can affect how prazosin works. Possible interactions with other medicines can affect Minipress (prazosin) levels and increase the risk of severe adverse reactions. The following medications can have interactions with prazosin:

Beta-blockers including propranolol (Inderal, others)
Other blood pressure medications
Medications prescribed for erectile dysfunction (ED), such as tadalafil (Cialis, Adcirca), sildenafil (Viagra), and vardenafil (Staxyn, Levitra)

The above list may not describe all the potential interactions of prazosin. Give your doctor or pharmacist a list of all the medicines you are taking, including prescription drugs, nonprescription drugs, dietary supplements, and herbal remedies. Also, tell your healthcare professional if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription and over-the-counter medications.

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