Minipress 5mg Capsules
It is used to treat high blood pressure.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Antihypertensive; Benign Prostatic Hyperplasia (BPH) Agent
Pharmacologic Class
Alpha-1 Adrenergic Blocker
Pregnancy Category
Category C
FDA Approved
Jun 1976
DEA Schedule
Not Controlled
Overview
What is this medicine?
Prazosin is a medication that helps relax blood vessels, which lowers blood pressure. It can also relax muscles in the prostate and bladder to improve urine flow in men with an enlarged prostate. It's important to take it exactly as prescribed and be aware of potential dizziness, especially when standing up.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food. Continue taking it even if you feel well, unless your doctor or healthcare provider advises you to stop.
Storing and Disposing of Your Medication
Store your medication at room temperature, protected from light and moisture. Keep it in a dry place, away from bathrooms. Ensure all medications are stored safely and out of reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you're unsure about disposal, consult your pharmacist. You may also have access to local drug take-back programs.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Avoid taking two doses at the same time or taking extra doses.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food. Continue taking it even if you feel well, unless your doctor or healthcare provider advises you to stop.
Storing and Disposing of Your Medication
Store your medication at room temperature, protected from light and moisture. Keep it in a dry place, away from bathrooms. Ensure all medications are stored safely and out of reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you're unsure about disposal, consult your pharmacist. You may also have access to local drug take-back programs.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Avoid taking two doses at the same time or taking extra doses.
Lifestyle & Tips
- Avoid sudden changes in position (e.g., rising quickly from sitting or lying down) to prevent dizziness or fainting.
- Avoid or limit alcohol consumption, as it can increase the risk of dizziness and low blood pressure.
- Be cautious when driving or operating machinery, especially when starting the medication or increasing the dose, until you know how it affects you.
- Stay hydrated, especially in hot weather or during exercise, to help prevent low blood pressure.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
Hypertension: Initial 1 mg orally 2-3 times daily; titrate slowly based on response. Usual maintenance 6-15 mg/day in divided doses. BPH: Initial 0.5 mg orally 2-3 times daily; titrate slowly. Usual maintenance 2-5 mg orally 2 times daily.
Dose Range:
0.5 - 40 mg
Condition-Specific Dosing:
Hypertension:
Initial 1 mg BID or TID; maintenance 6-15 mg/day in divided doses (max 20 mg/day, rarely up to 40 mg/day).
Benign Prostatic Hyperplasia (BPH):
Initial 0.5 mg BID or TID; maintenance 2-5 mg BID.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established for routine hypertension; off-label use for PTSD nightmares (0.5-5 mg at bedtime) or pheochromocytoma (dosing individualized).
Adolescent:
Not established for routine hypertension; off-label use for PTSD nightmares (0.5-5 mg at bedtime) or pheochromocytoma (dosing individualized).
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment, but caution advised.
Moderate:
No specific adjustment, but caution advised; slower titration may be prudent.
Severe:
No specific adjustment, but caution advised; slower titration and close monitoring recommended.
Dialysis:
Prazosin is highly protein-bound and not significantly dialyzable. No specific dose adjustment for dialysis patients, but monitor for exaggerated hypotensive response.
Hepatic Impairment:
Mild:
No specific adjustment, but caution advised.
Moderate:
Caution advised; slower titration and close monitoring recommended due to extensive hepatic metabolism.
Severe:
Caution advised; slower titration and close monitoring recommended due to extensive hepatic metabolism.
Pharmacology
Mechanism of Action
Prazosin is a selective competitive antagonist of postsynaptic alpha-1 adrenergic receptors. This blockade leads to relaxation of vascular smooth muscle, resulting in vasodilation of both arterioles and venules, thereby reducing peripheral vascular resistance and venous return. This action lowers blood pressure. In benign prostatic hyperplasia (BPH), alpha-1 blockade relaxes smooth muscle in the prostate and bladder neck, improving urine flow.
Pharmacokinetics
Absorption:
Bioavailability:
50-70%
Tmax:
2-3 hours
FoodEffect:
Food may delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
0.5 L/kg
ProteinBinding:
Approximately 95%
CnssPenetration:
Limited, but crosses the blood-brain barrier to some extent (explains off-label use for PTSD nightmares).
Elimination:
HalfLife:
2-4 hours
Clearance:
Not available
ExcretionRoute:
Primarily bile and feces (6-10% unchanged drug), minor renal excretion.
Unchanged:
6-10%
Pharmacodynamics
OnsetOfAction:
Approximately 30-60 minutes
PeakEffect:
2-4 hours
DurationOfAction:
Up to 10 hours (dose-dependent)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Attention Immediately
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Fast or abnormal heartbeat
A painful erection (priapism) or an erection that lasts longer than 4 hours, which can occur even when you are not having sex. If left untreated, this condition may lead to permanent sexual dysfunction.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Dizziness
Drowsiness
Fatigue
Weakness
Headache
Upset stomach
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice on managing side effects.
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Fast or abnormal heartbeat
A painful erection (priapism) or an erection that lasts longer than 4 hours, which can occur even when you are not having sex. If left untreated, this condition may lead to permanent sexual dysfunction.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Dizziness
Drowsiness
Fatigue
Weakness
Headache
Upset stomach
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice on managing side effects.
Seek Immediate Medical Attention If You Experience:
- Severe dizziness or lightheadedness
- Fainting (syncope)
- Rapid or irregular heartbeat
- Chest pain
- Difficulty breathing
- Swelling of the face, lips, tongue, or throat (signs of allergic reaction)
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist identify potential interactions between this medication and other substances you are taking.
* Any health problems you have, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that it is safe to take this medication with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist identify potential interactions between this medication and other substances you are taking.
* Any health problems you have, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that it is safe to take this medication with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
To ensure your safety, avoid driving or engaging in activities that require alertness for 24 hours after taking your first dose, as well as after any dose increase or when restarting the medication after a period of stopping it. Before resuming these activities, make sure you understand how this medication affects you.
To minimize the risk of dizziness or fainting, get up slowly from a sitting or lying down position. Be cautious when climbing stairs.
Follow your healthcare provider's instructions for monitoring your blood pressure.
This medication may interfere with certain laboratory tests. Be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication.
If you are scheduled to undergo cataract surgery or any other eye procedure, consult with your doctor beforehand.
Before using any over-the-counter (OTC) products that may increase blood pressure, such as cough or cold medications, diet pills, stimulants, non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, or certain natural products or aids, discuss their use with your doctor.
Also, talk to your doctor before consuming alcohol. In hot weather or during physical activity, be cautious and drink plenty of fluids to avoid dehydration.
If you are pregnant, planning to become pregnant, or are breastfeeding, inform your doctor. You will need to discuss the potential benefits and risks of this medication to both you and your baby.
To ensure your safety, avoid driving or engaging in activities that require alertness for 24 hours after taking your first dose, as well as after any dose increase or when restarting the medication after a period of stopping it. Before resuming these activities, make sure you understand how this medication affects you.
To minimize the risk of dizziness or fainting, get up slowly from a sitting or lying down position. Be cautious when climbing stairs.
Follow your healthcare provider's instructions for monitoring your blood pressure.
This medication may interfere with certain laboratory tests. Be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication.
If you are scheduled to undergo cataract surgery or any other eye procedure, consult with your doctor beforehand.
Before using any over-the-counter (OTC) products that may increase blood pressure, such as cough or cold medications, diet pills, stimulants, non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, or certain natural products or aids, discuss their use with your doctor.
Also, talk to your doctor before consuming alcohol. In hot weather or during physical activity, be cautious and drink plenty of fluids to avoid dehydration.
If you are pregnant, planning to become pregnant, or are breastfeeding, inform your doctor. You will need to discuss the potential benefits and risks of this medication to both you and your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension (very low blood pressure)
- Drowsiness
- Tachycardia (rapid heart rate)
- Shock
What to Do:
Seek immediate medical attention. Call 911 or your local emergency number. For advice, call a poison control center at 1-800-222-1222. Management typically involves supporting blood pressure with IV fluids and, if necessary, vasopressors. Keep the patient in a supine position.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil): Concomitant use can lead to additive hypotensive effects and symptomatic hypotension.
- Beta-blockers: May enhance the hypotensive effect of prazosin.
Moderate Interactions
- Other antihypertensives (e.g., diuretics, ACE inhibitors, ARBs, CCBs): Additive hypotensive effects.
- Alcohol: May potentiate orthostatic hypotensive effects.
- NSAIDs (e.g., ibuprofen, naproxen): May reduce the antihypertensive effect of prazosin.
- Alpha-adrenergic agonists (e.g., phenylephrine, pseudoephedrine): May antagonize the hypotensive effect of prazosin.
Monitoring
Baseline Monitoring
Blood Pressure (supine and standing)
Rationale: To establish baseline and assess for orthostatic hypotension risk.
Timing: Prior to initiation and before each dose titration.
Heart Rate
Rationale: To establish baseline and monitor for reflex tachycardia.
Timing: Prior to initiation and during dose titration.
Renal Function (BUN, Creatinine)
Rationale: To assess baseline kidney function, though dose adjustment is generally not required for mild-moderate impairment.
Timing: Prior to initiation.
Liver Function Tests (LFTs)
Rationale: To assess baseline hepatic function, as prazosin is extensively metabolized by the liver.
Timing: Prior to initiation.
Routine Monitoring
Blood Pressure (supine and standing)
Frequency: Frequently during initial titration (e.g., daily for first week), then periodically (e.g., weekly to monthly) once stable.
Target: Individualized, typically <130/80 mmHg for hypertension.
Action Threshold: Significant orthostatic drop (>20 mmHg systolic or >10 mmHg diastolic) or symptomatic hypotension; inadequate BP control.
Heart Rate
Frequency: Periodically, especially during titration.
Target: 60-100 bpm (unless otherwise indicated).
Action Threshold: Persistent tachycardia or bradycardia.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Syncope (fainting), especially 'first-dose syncope'
- Palpitations
- Headache
- Nausea
- Fatigue
Special Patient Groups
Pregnancy
Prazosin is classified as Pregnancy Category C. Animal studies have shown adverse effects on the fetus, but there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Trimester-Specific Risks:
First Trimester:
Potential for fetal harm based on animal data; human data limited.
Second Trimester:
Potential for fetal harm based on animal data; human data limited.
Third Trimester:
Potential for fetal harm based on animal data; human data limited. Risk of neonatal hypotension if used close to delivery.
Lactation
Prazosin is excreted in small amounts into breast milk. The amount is generally considered low and unlikely to cause adverse effects in a healthy, full-term infant. However, monitor the infant for signs of hypotension (e.g., lethargy, poor feeding).
Infant Risk:
L3 (Moderately safe; low levels in milk, generally considered compatible with monitoring).
Pediatric Use
Safety and efficacy have not been established for routine use in pediatric patients for hypertension. It is used off-label for specific conditions like PTSD-related nightmares or pheochromocytoma, with dosing individualized and close monitoring.
Geriatric Use
Elderly patients may be more sensitive to the hypotensive effects of prazosin, particularly orthostatic hypotension and first-dose syncope. A lower initial dose and slower titration are recommended. Monitor blood pressure closely, especially standing blood pressure.
Clinical Information
Clinical Pearls
- First-dose syncope is a known adverse effect; to minimize risk, administer the initial dose at bedtime and titrate the dose slowly.
- Advise patients to rise slowly from a sitting or lying position to prevent orthostatic hypotension.
- Tolerance to the hypotensive effect may develop over time, requiring dose adjustments.
- Prazosin can be effective for PTSD-related nightmares, often prescribed off-label for this indication.
- Patients should be advised to report any prolonged or painful erection (priapism), though this is rare with prazosin.
Alternative Therapies
- Other alpha-1 adrenergic blockers (e.g., terazosin, doxazosin, alfuzosin, tamsulosin, silodosin) for hypertension or BPH.
- For hypertension: Thiazide diuretics, ACE inhibitors, Angiotensin Receptor Blockers (ARBs), Calcium Channel Blockers (CCBs), Beta-blockers.
- For BPH: 5-alpha-reductase inhibitors (e.g., finasteride, dutasteride), anticholinergics (for overactive bladder symptoms), phosphodiesterase-5 inhibitors (e.g., tadalafil).
Cost & Coverage
Average Cost:
Varies, typically low for generic per 30 capsules
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (for generic formulations)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.