Minipress (Prazosin)
Complete patient guide for uses, dosage, side effects, and safety information
Prescription RequiredQuick Facts
What Is Minipress Used For?
Minipress contains prazosin, which belongs to a group of medicines called alpha blockers. These medications work by relaxing the muscles in blood vessel walls and reducing resistance to blood flow.
Primary Uses
Minipress is used to treat high blood pressure (hypertension), benign prostatic hyperplasia or BPH (prostate trouble) in men waiting for prostate surgery, Raynaud’s disease where fingers become white and painful when cold, and certain types of heart failure. When treating high blood pressure or heart failure, it’s often used with other medicines.
How It Works
Alpha blockers like Minipress work by relaxing muscles in the walls of blood vessels, which reduces resistance to blood flow and lowers blood pressure. For prostate problems, it relaxes muscles in the prostate gland and increases urine flow.
How to Take Minipress
Minipress should be started at a low dose to reduce the risk of blood pressure dropping too much, which can cause dizziness, lightheadedness, or fainting.
Dosage Instructions
Start with 0.5 mg (half a 1 mg tablet) taken twice daily. Your doctor may gradually increase this dose based on your condition. For high blood pressure: usual starting dose is 0.5 mg twice daily, increasing to 1 mg two or three times daily, up to 20 mg daily in divided doses. For heart failure: start with 0.5 mg, increasing to 4 mg daily in three or four doses, up to 20 mg daily. For Raynaud’s disease: start with 0.5 mg twice daily, may increase to 1-2 mg twice daily. For prostate problems: start with 0.5 mg twice daily, may increase to 2 mg twice daily. Take at the same time each day. When starting or increasing dose, take the first dose at bedtime.
What If You Miss a Dose?
If you miss a dose and it’s within 3 hours of your next dose, skip the missed dose and take the next one as scheduled. Otherwise, take it as soon as you remember, then return to your normal schedule. If you miss two or more doses, you’ll need to restart at a low dose and build up gradually – ask your doctor how to do this.
Important: Never take a double dose to make up for a missed dose. Be especially careful if you need to get up during the night when starting treatment, as you may feel dizzy and could fall.
Available Tablet Strengths
Side Effects
Like all medications, this medicine can cause side effects. Most are mild and temporary, but some require medical attention.
Common Side Effects
These side effects occur relatively frequently and usually don’t require emergency care:
- feeling sick, vomiting or dry mouth
- constipation, diarrhea
- weakness or lack of energy
- headache or drowsiness
- stuffy nose
Seek immediate medical attention if you experience:
- fast or pounding heartbeat, chest pain
- fainting, dizziness or lightheadedness when standing up
- shortness of breath or difficulty breathing
- blurred vision
- rash, itching or other skin problems
- sharp pain in the stomach or back
- persistent painful erection of the penis which occurs without sexual arousal
- tingling or numbness of the hands or feet
- swelling of the hands, feet or ankles
- feelings of nervousness or depression
Important Warnings
There are several important conditions and situations where Minipress should not be used or requires special caution.
Who Should Not Take Minipress
Do not take Minipress if you are allergic to prazosin or any ingredients in the medicine, if you are allergic to any other alpha blocker medicine, or if you are under 12 years of age. Signs of allergic reaction include shortness of breath, wheezing, swelling of face/lips/tongue, or skin rash.
Medical Conditions to Discuss
Tell your doctor if you have heart problems such as heart failure or angina, kidney or liver problems, or allergies to other medicines, foods, preservatives, or dyes. Also inform your doctor about all other medicines you’re taking.
Pregnancy and Breastfeeding
Check with your doctor if you are pregnant, planning to become pregnant, breastfeeding, or planning to breastfeed. Tell your doctor immediately if you become pregnant while taking Minipress.
Elderly Patients: If you are 65 years or older, you should be especially careful while taking Minipress and report any side effects promptly to your doctor. Dizziness and lightheadedness symptoms can be particularly dangerous if you’re elderly and have heart disease.
Drug Interactions
Some medicines may interfere with Minipress and affect how it works. Tell your doctor about all medicines, vitamins, or supplements you’re taking.
Blood Pressure Medicines: Other blood pressure medicines may have an additive effect with Minipress and make your blood pressure too low, so their dose may need adjustment when starting Minipress.
- medicines used to lower blood pressure
- fluid tablets (diuretics)
- medicines to treat impotence (erectile dysfunction)
Alcohol & Driving
Minipress can affect your ability to drive and may interact with alcohol, so special precautions are needed.
Alcohol
Be careful to limit alcohol while taking Minipress. Dizziness, lightheadedness, or fainting is more likely if you drink alcohol. Tell your doctor if you drink alcohol.
Driving and Operating Machinery
Be careful driving or operating machinery until you know how Minipress affects you. The medicine may cause dizziness, lightheadedness, fainting, blurred vision, or drowsiness, especially after the first dose or dose increases. Make sure you know how you react before driving or doing anything that could be dangerous.
Temperature Regulation
Take extra care during exercise, hot weather, or if you have to stand for a long time, as dizziness and lightheadedness are more likely to occur in these situations.
Storage
Keep tablets in their original pack until time to take them. Store in a cool, dry place where temperature stays below 30°C. Don’t store in the bathroom, near a sink, in the car, or on window sills. Keep away from moisture, heat, and sunlight. Keep out of reach of children. Don’t use after expiry date.
Overdose Information
If you take too much Minipress, you may feel lightheaded, dizzy, have a fast or irregular heartbeat, or faint. If overdose is suspected, immediately phone the Poisons Information Centre (13 11 26), contact your doctor, or go to the nearest hospital Emergency Department, even if there are no symptoms.
Frequently Asked Questions
Minipress starts working to lower blood pressure relatively quickly, but you may need to take it for a long time for conditions like high blood pressure, heart failure, or Raynaud’s disease. For prostate problems, you’ll only need to take it until your operation.
Yes, it doesn’t matter if you take Minipress before or after food. Swallow the tablets with a glass of water or other liquid.
Do not stop taking Minipress or lower the dosage without checking with your doctor. Your doctor will reduce your dose gradually if you need to stop taking this medicine.
Be careful to limit alcohol while taking Minipress. Dizziness, lightheadedness, or fainting is more likely if you drink alcohol, stand for long periods, exercise, or are in hot weather.
Starting with a low dose of 0.5 mg twice daily reduces the risk of too great a drop in blood pressure, which can make you dizzy, lightheaded, or faint. Your doctor may gradually increase the dose as needed.
Get up slowly after sitting or lying down. If you feel dizzy or lightheaded, lie down so you don’t faint, then sit for a few moments before standing to prevent dizziness from returning. If symptoms continue, tell your doctor.
If you are 65 years or older, you should be especially careful while taking Minipress and report any side effects promptly to your doctor. Dizziness and lightheadedness can be particularly dangerous if you’re elderly and have heart disease.
Important Disclaimer
This information is intended for general educational purposes only and should not be considered medical advice. Always consult your healthcare provider or pharmacist before starting, stopping, or changing any medication.
If you think you may have a medical emergency, call your doctor or emergency services immediately.