Prazosin 1mg 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
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 help improve urine flow in men with an enlarged prostate and reduce nightmares in people with PTSD.
How to Use This Medicine
Taking Your Medication
To get the most benefit from your medication, it's essential to take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. You can take this medication with or without food. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature, protected from light, and in a dry place. Avoid storing it in a bathroom. Keep all medications in a secure location, out of the reach of children and pets. When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs in your area.
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. Do not take two doses at the same time or take extra doses to make up for the missed one.
To get the most benefit from your medication, it's essential to take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. You can take this medication with or without food. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature, protected from light, and in a dry place. Avoid storing it in a bathroom. Keep all medications in a secure location, out of the reach of children and pets. When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs in your area.
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. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take the first dose, and any new increased doses, at bedtime to minimize the 'first-dose phenomenon' (sudden drop in blood pressure).
- Avoid sudden changes in position (e.g., standing up quickly from sitting or lying down) to prevent dizziness or fainting.
- Be cautious when driving or operating machinery, especially when starting the medication or increasing the dose, until you know how it affects you.
- Avoid alcohol, as it can increase the blood pressure-lowering effect.
- Stay well-hydrated, especially in hot weather or during exercise.
- Report any persistent dizziness, lightheadedness, or fainting spells to your doctor.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Hypertension: Initially 1 mg orally 2-3 times daily. Titrate slowly based on response.
Dose Range:
1 - 20 mg
Condition-Specific Dosing:
Hypertension (initial):
1 mg orally 2-3 times daily
Hypertension (maintenance):
6-15 mg/day in divided doses (max 20 mg/day)
Benign Prostatic Hyperplasia (off-label):
Initially 0.5 mg-1 mg at bedtime, titrate to 2-5 mg daily
PTSD-related nightmares (off-label):
Initially 1 mg at bedtime, titrate to 2-15 mg at bedtime
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established for routine use; limited off-label use for hypertension or PTSD in specific cases, typically starting at 0.05 mg/kg/day divided 3 times daily, titrating slowly.
Adolescent:
Not established for routine use; limited off-label use for hypertension or PTSD in specific cases, typically starting at 0.05 mg/kg/day divided 3 times daily, titrating slowly.
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment needed, but monitor response.
Moderate:
No specific adjustment needed, but monitor response.
Severe:
Consider lower initial dose (e.g., 0.5 mg) and slower titration due to potential for increased sensitivity.
Dialysis:
Prazosin is not dialyzable. No specific supplemental dose needed, but monitor for exaggerated hypotensive response.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
Use with caution; consider lower initial dose and slower titration due to extensive hepatic metabolism.
Severe:
Use with caution; consider lower initial dose and slower titration due to extensive hepatic metabolism. Monitor closely for adverse effects.
Pharmacology
Mechanism of Action
Prazosin is a selective alpha-1 adrenergic receptor blocker. It competitively inhibits the binding of norepinephrine to alpha-1 receptors on vascular smooth muscle, leading to vasodilation of both arterioles and venules. This reduces peripheral vascular resistance and venous return, resulting in a decrease in blood pressure. In benign prostatic hyperplasia (BPH), it 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
Elimination:
HalfLife:
2-4 hours
Clearance:
Not available
ExcretionRoute:
Primarily bile and feces (6-10% unchanged drug), small amount via urine (approximately 10% unchanged drug)
Unchanged:
Approximately 6-10% (feces), approximately 10% (urine)
Pharmacodynamics
OnsetOfAction:
Approximately 30-60 minutes
PeakEffect:
Approximately 2-4 hours
DurationOfAction:
Approximately 6-10 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
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. Although many people do not experience any side effects or only have mild ones, it is 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.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
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. Although many people do not experience any side effects or only have mild ones, it is 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.
Seek Immediate Medical Attention If You Experience:
- Severe dizziness or lightheadedness
- Fainting (syncope)
- Rapid or irregular heartbeat
- Chest pain
- Swelling in ankles or feet
- Persistent nausea or vomiting
- Priapism (prolonged erection, rare but serious)
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, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
Potential interactions with other medications or health conditions. To ensure safe use, disclose all prescription and over-the-counter (OTC) medications, natural products, and vitamins you are taking.
* Any existing health problems, as they may affect the safety of taking this medication.
To avoid potential interactions, do not start, stop, or change the dosage of any medication without first consulting your doctor. It is crucial to verify that it is safe to take this medication in combination with your other medications and health conditions.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
Potential interactions with other medications or health conditions. To ensure safe use, disclose all prescription and over-the-counter (OTC) medications, natural products, and vitamins you are taking.
* Any existing health problems, as they may affect the safety of taking this medication.
To avoid potential interactions, do not start, stop, or change the dosage of any medication without first consulting your doctor. It is crucial to verify that it is safe to take this medication in combination with your other medications and health conditions.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
After taking your first dose, or if your dose is increased, or if you restart this medication after stopping it, do not drive or engage in activities that require you to be alert for 24 hours. Before driving or performing other tasks, 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.
Monitor your blood pressure as directed by your healthcare provider. Be aware that this medication may interfere with certain laboratory tests, so inform 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. Before using 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 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 breastfeeding, inform your doctor. You will need to discuss the potential benefits and risks of this medication to both you and your baby.
After taking your first dose, or if your dose is increased, or if you restart this medication after stopping it, do not drive or engage in activities that require you to be alert for 24 hours. Before driving or performing other tasks, 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.
Monitor your blood pressure as directed by your healthcare provider. Be aware that this medication may interfere with certain laboratory tests, so inform 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. Before using 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 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 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)
- Dizziness
- Drowsiness
- Tachycardia (rapid heart rate)
- Shock
- Loss of consciousness
What to Do:
In case of suspected overdose, seek immediate medical attention. Call 911 or your local emergency number. For poison control, call 1-800-222-1222. Management typically involves supporting blood pressure with intravenous fluids and vasopressors if needed. Keep the person lying down with legs elevated.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil): Concomitant use can lead to additive hypotensive effects, potentially causing symptomatic hypotension. Avoid or use with extreme caution, starting with lowest doses of both agents and separating administration times.
- Other antihypertensives (e.g., beta-blockers, diuretics, ACE inhibitors, ARBs, calcium channel blockers): Additive hypotensive effects. Requires careful monitoring and dose adjustment.
Moderate Interactions
- NSAIDs (e.g., ibuprofen, naproxen): May reduce the antihypertensive effect of prazosin.
- Alcohol: May enhance the hypotensive effects of prazosin.
- Alpha-adrenergic agonists (e.g., pseudoephedrine, phenylephrine): May antagonize the hypotensive effect of prazosin.
- Antipsychotics (e.g., clozapine): Increased risk of orthostatic hypotension.
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Blood Pressure (sitting and standing)
Rationale: To establish baseline and assess for orthostatic hypotension before initiating therapy.
Timing: Prior to first dose
Heart Rate
Rationale: To establish baseline and monitor for reflex tachycardia.
Timing: Prior to first dose
Renal Function (SCr, BUN)
Rationale: To assess baseline kidney function, especially in patients with comorbidities, as severe impairment may warrant lower initial dose.
Timing: Prior to initiation, if clinically indicated
Hepatic Function (ALT, AST, bilirubin)
Rationale: To assess baseline liver function, especially in patients with comorbidities, as severe impairment may warrant lower initial dose.
Timing: Prior to initiation, if clinically indicated
Routine Monitoring
Blood Pressure (sitting and standing)
Frequency: Regularly during dose titration (e.g., daily for first few days, then weekly) and periodically thereafter (e.g., monthly to quarterly) once stable.
Target: Individualized, typically <130/80 mmHg for hypertension, or symptom improvement for BPH/PTSD.
Action Threshold: Significant orthostatic drop (>20 mmHg systolic or >10 mmHg diastolic), symptomatic hypotension, or inadequate blood pressure control.
Heart Rate
Frequency: During dose titration and periodically thereafter.
Target: 60-100 bpm (unless otherwise indicated)
Action Threshold: Persistent tachycardia or bradycardia outside normal limits.
Symptoms of Orthostatic Hypotension
Frequency: Daily, especially during initial therapy and dose increases.
Target: Absence of dizziness, lightheadedness, syncope.
Action Threshold: Presence of symptoms, requiring dose adjustment or patient education.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Fainting (syncope)
- Palpitations
- Headache
- Nausea
- Fatigue
- Nasal congestion
Special Patient Groups
Pregnancy
Prazosin is Pregnancy Category C. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects, but there are no adequate and well-controlled studies in pregnant women.
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 American Academy of Pediatrics considers it compatible with breastfeeding. Monitor the infant for signs of hypotension (e.g., lethargy, poor feeding).
Infant Risk:
Low risk; monitor for sedation or hypotension.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established for hypertension. Off-label use for hypertension or PTSD-related nightmares in children and adolescents has been reported, but requires careful titration and monitoring due to potential for exaggerated hypotensive response.
Geriatric Use
Elderly patients may be more sensitive to the hypotensive effects of prazosin, particularly the 'first-dose phenomenon' and orthostatic hypotension. Start with lower doses (e.g., 0.5 mg) and titrate slowly. Monitor blood pressure closely, especially standing blood pressure.
Clinical Information
Clinical Pearls
- **First-Dose Phenomenon**: Prazosin can cause a sudden and severe drop in blood pressure (orthostatic hypotension), sometimes leading to syncope (fainting), especially with the first dose or when the dose is increased. To minimize this, administer the first dose and any subsequent dose increases at bedtime.
- **Titration**: Dose titration should be slow and gradual to allow for adaptation and minimize adverse effects.
- **Off-label Uses**: Prazosin is widely used off-label for PTSD-related nightmares and benign prostatic hyperplasia (BPH) due to its alpha-1 blocking properties.
- **Fluid Status**: Patients should be adequately hydrated to reduce the risk of hypotension.
- **Cataract Surgery**: Intraoperative Floppy Iris Syndrome (IFIS) has been observed during cataract surgery in some patients treated with alpha-1 blockers. Inform ophthalmologists of prazosin use.
Alternative Therapies
- Other alpha-1 blockers (e.g., terazosin, doxazosin, tamsulosin, alfuzosin, silodosin)
- Other classes of antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers, calcium channel blockers, diuretics)
- For BPH: 5-alpha reductase inhibitors (e.g., finasteride, dutasteride), anticholinergics, beta-3 agonists, surgical options.
- For PTSD: SSRIs (e.g., sertraline, paroxetine), SNRIs, psychotherapy (e.g., CBT, EMDR).
Cost & Coverage
Average Cost:
Varies widely, typically $10-$50 per 30 capsules (1mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. 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 it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with 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 detailed information about the overdose, including the medication taken, the amount, and the time it occurred.