Minipress (Prazosin) - Oral

What Is Minipress?

Minipress (prazosin) is a prescription medication called an alpha-1 blocker used to treat hypertension (high blood pressure).

Minipress works by blocking the release of chemicals that stimulate the narrowing of your blood vessels, which causes your blood pressure to increase. Inhibiting this chemical allows the blood vessels to relax, contributing to lower blood pressure.

Prazosin is usually not the first line of treatment for high blood pressure. Typically, it is used with other antihypertensive agents when blood pressure is uncontrolled. 

This medication is available in capsule form to be taken orally (by mouth).

Drug Facts

Generic Name: Prazosin

Brand Name(s): Minipress

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Alpha-1 blocker

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Prazosin hydrochloride

Dosage Form(s): Capsule

What Is Minipress Used For?

Minipress, or prazosin, is approved to treat high blood pressure. It may be used alone or in addition to other medications, such as diuretics or beta-adrenergic blocking agents.

Medication should be part of a comprehensive plan to achieve blood pressure control that combines pharmacologic therapy with lifestyle adjustments, such as diet changes and exercise.

How to Take Minipress 

Take prazosin as instructed by your healthcare provider and follow their directions as stated.

Minipress is prescribed as a capsule and should be taken by mouth with water. You can take it with or without food. The general frequency of dosing of prazosin is two to three times a day. Your provider will determine the best dosage based on your blood pressure.

Prazosin can make you feel dizzy or faint after standing up too quickly from a sudden drop in blood pressure. If dizziness or lightheadedness continues after a week, contact your healthcare provider to adjust the dose or ask for an alternative medication. 

Storage

Store Minipress at room temperature (between 68 F and 77 F) and away from moisture. Storing your medication in hot and cold temperatures can prevent the medication from working correctly.

As always, ensure your medication is stored in a safe place that is out of reach for children and pets to prevent accidental consumption. Contact your pharmacy or healthcare provider to request a refill if you are low on medication.

Off-Label Uses

Other than lowering your blood pressure, your healthcare provider can prescribe Minipress to help treat other health conditions, such as:

However, the U.S. Food and Drug Administration (FDA) does not approve these uses.

How Long Does Minipress Take to Work? 

Minipress' blood pressure-lowering effects begin within two to four hours after taking it. You may not see the full benefits of taking this medication for four to six weeks.

What Are the Side Effects of Minipress?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at www.fda.gov/medwatch or 800-FDA-1088.

Common Side Effects 

The following side effects commonly reported while taking Minipress include:

  • Feeling dizzy or light-headed
  • Fainting
  • Lack of energy
  • Headache
  • Palpitations
  • Nausea

Severe Side Effects 

Do not hesitate to contact your healthcare provider right away if you are experiencing any of these severe side effects. Call 911 immediately if you feel your life is at risk or believe you require medical assistance.

Rare but serious side effects include:

  • Signs of an allergic reaction, such as hives, rashes, and shortness of breath
  • Abnormal heartbeat
  • Chest pain
  • Long-lasting painful erection, known as priapism

Long-Term Side Effects 

No long-term side effects are associated with Minipress. However, you should contact your healthcare provider if you still have dizziness or fainting episodes after one week of taking prazosin.

Do not suddenly stop taking prazosin as it can cause your blood pressure to increase rapidly. 

Report Side Effects

Minipress may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Minipress Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (capsules):
    • For high blood pressure:
      • Adults—At first, 1 milligram (mg) 2 or 3 times a day. Your doctor will slowly increase your dose as needed. However, the dose is usually not more than 20 mg per day.
      • Children—Use and dose must be determined by your doctor.

Modifications 

Before starting prazosin, talk to your healthcare provider about any concerns regarding the dosage of Minipress. If you have mild or moderate kidney or liver problems, it is safe to take prazosin at its regular dosage. 

Children can take Minipress if other blood pressure medications do not work. Your child’s healthcare provider will calculate an appropriate dosage based on your child’s weight.

There are limited studies regarding the safety of taking prazosin while pregnant or breastfeeding. Talk to your healthcare provider about other safe blood pressure medications to take while pregnant or breastfeeding.

Missed Dose

If you miss a dose, take the missed dose as soon as you remember. You must only take one dose at a time, so do not take two doses simultaneously to make up for the missed dose. Taking more Minipress than prescribed can cause your blood pressure to become dangerously low. 

Overdose: What Happens If I Take Too Much Minipress?

There are limited reports of how much Minipress can cause an overdose. However, it is generally advised not to take more than three doses within 24 hours. Taking any greater amount can put you at dangerously low blood pressure.

Common symptoms of extremely low blood pressure include:

  • Dizziness or lightheadedness
  • Fainting
  • Nausea
  • Dehydration and unusual thirst
  • Inability to concentrate
  • Blurred vision
  • Cold, clammy, and pale skin
  • Rapid, shallow breathing
  • Fatigue
  • Mood changes 

What Happens If I Overdose on Minipress?

If you think you or someone else may have overdosed on Minipress, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Minipress, call 911 immediately.

Precautions

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It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Dizziness, lightheadedness, or fainting may occur after you use this medicine, especially when you get up from a lying or sitting position. Getting up slowly may help lessen this problem. If you feel dizzy, lie down so you do not faint. Then sit for a few moments before standing to prevent the dizziness from returning.

You may also have dizziness, lightheadedness, or fainting if you drink alcohol, stand for a long time, exercise or if the weather is hot. While you are taking this medicine, be careful to limit the amount of alcohol you drink. Drink plenty of fluids if you exercise or sweat more than usual while you are using this medicine.

Prazosin may cause some people to become dizzy, drowsy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy, drowsy, or are not alert.

Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.

Call your doctor right away if you have a prolonged erection of the penis while you are using this medicine. It must be treated right away to prevent permanent impotence.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Minipress?

You should not take Minipress if any of these conditions apply to you:

  • An allergy to alpha-1 blockers, such as prazosin, doxazosin, and terazosin
  • A history of fainting easily when standing too quickly or moving to an upright position
  • Stressed or mixed urinary incontinence, as prazosin may cause your urination problems to worsen 
  • Older than 65 years (prazosin is not recommended to treat high blood pressure in this population). Your healthcare provider will most likely prescribe a safer medication to help lower your blood pressure.
  • If you're planning to have cataract surgery, Minipress can put you at risk of floppy iris syndrome. Floppy iris syndrome is when the iris loses its structural form. It can cause complications during cataract surgery. Tell your eye doctor that you are taking prazosin before surgery. 

What Other Medications Interact With Minipress?

When taking Minipress, you must be aware that medications or supplements can worsen your side effects or make the drug less effective.

Some medications can increase the blood pressure-lowering effects and enhance certain side effects. These include:

What Medications Are Similar?

Other alpha-1 blockers that can help lower your blood pressure are:

  • Terazosin
  • Cardura (doxazosin)

Even though alpha-1 blockers can help lower your blood pressure, they are not the first line of treatment used to treat high blood pressure. Instead, alpha-1 blockers are combined with other blood pressure medications when your blood pressure is difficult to control.

Common first-line treatment medications include: 

This is a list of drugs also prescribed for hypertension. Your healthcare provider will determine your proper treatment regimen based on your current blood pressure control.

Frequently Asked Questions

  • Is it safe to take Minipress with my other blood pressure medications?

    Prazosin is safe to take with most other blood pressure medications. However, you should not take Minipress with other alpha-1 blockers, as it can put you at risk for adverse side effects. It is best to contact your healthcare provider as they can safely prescribe other blood pressure medications.

  • When would be the best time to take Minipress?

    Since dizziness and drowsiness are common side effects, taking your first dose of prazosin at bedtime is recommended. After a few days, your body should get used to the medication, and the side effects will gradually disappear. Then, you can take the medication whenever it is most convenient.

  • Can Minipress be used to help with my PTSD?

    Yes, prazosin can be used off-label to help people with post-traumatic stress disorder to aid them during sleep by preventing nightmares. This is an off-label use, meaning the FDA does not approve it. Talk to your healthcare provider about whether this is an option for you.

  • Can I drink alcohol while taking Minipress?

    No, you should avoid drinking alcohol because it can cause your blood pressure to fall extremely low and put you at risk of a fainting episode. 

How Can I Stay Healthy While Taking Minipress?

To stay healthy while taking Minipress, it is important to take this medication as instructed by your healthcare provider.

Even if you feel better, you must continue to take prazosin as prescribed. Suddenly stopping prazosin can cause your blood pressure to rise rapidly. Moreover, since prazosin can make you feel dizzy or faint, avoid being in hot temperatures, standing for long periods, or drinking alcohol, as these circumstances can enhance these side effects.

Lifestyle changes like light exercise and a low-sodium diet can help you achieve your blood pressure goals and feel better faster. Changing your lifestyle can be difficult, so start small and gradually work your way up. Your healthcare provider can let you know what level of activity and lifestyle change would be right for you.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.


The author would like to recognize and thank Alexya Rosas for contributing to this article.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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