Prazosin 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
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 used to lower high blood pressure. It works by relaxing blood vessels, allowing blood to flow more easily. It can also be used off-label for certain conditions like enlarged prostate or nightmares related to PTSD.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided to you. Take your medication as directed, with or without food, and continue taking it even if you start to feel better. It's essential to follow your doctor's or healthcare provider's advice on dosage and duration of treatment.
Storing and Disposing of Your Medication
Store your medication at room temperature, protected from light, and in a dry place. Avoid storing it in a bathroom. Keep all medications in a safe 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, check with your pharmacist for guidance on the best disposal method or look into 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. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided to you. Take your medication as directed, with or without food, and continue taking it even if you start to feel better. It's essential to follow your doctor's or healthcare provider's advice on dosage and duration of treatment.
Storing and Disposing of Your Medication
Store your medication at room temperature, protected from light, and in a dry place. Avoid storing it in a bathroom. Keep all medications in a safe 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, check with your pharmacist for guidance on the best disposal method or look into 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. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Avoid sudden changes in position (e.g., standing up quickly from sitting or lying down) to prevent dizziness or fainting, especially with the first dose or dose increases.
- Avoid activities requiring mental alertness, such as driving or operating machinery, until you know how the medication affects you.
- Avoid alcohol, as it can increase dizziness and lightheadedness.
- Maintain adequate hydration.
- Follow a low-sodium diet and exercise regimen as advised by your doctor for blood pressure control.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Initial 1 mg orally two or three times daily; maintenance 6-15 mg/day in divided doses.
Dose Range:
1 - 40 mg
Condition-Specific Dosing:
hypertension:
Initial 1 mg orally two or three times daily. Dosage may be slowly increased to a total daily dose of 6-15 mg given in divided doses. Some patients may benefit from doses as high as 20 mg/day. Max 40 mg/day.
benign_prostatic_hyperplasia_off_label:
Initial 0.5 mg to 1 mg orally at bedtime. Titrate slowly based on response and tolerability, typically up to 2-5 mg once daily.
ptsd_nightmares_off_label:
Initial 1 mg orally at bedtime. Titrate slowly based on response and tolerability, typically up to 10-15 mg at bedtime.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established for hypertension. Off-label for PTSD-related nightmares: 0.5-1 mg orally at bedtime, titrate slowly to effect (e.g., 2-5 mg).
Adolescent:
Not established for hypertension. Off-label for PTSD-related nightmares: 0.5-1 mg orally at bedtime, titrate slowly to effect (e.g., 2-10 mg).
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment, use with caution.
Moderate:
No specific adjustment, use with caution; consider lower initial dose and slower titration.
Severe:
No specific adjustment, use with caution; consider lower initial dose and slower titration.
Dialysis:
Prazosin is not dialyzable. No specific adjustment, use with caution.
Hepatic Impairment:
Mild:
No specific adjustment, use with caution.
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.
Pharmacology
Mechanism of Action
Prazosin is a selective alpha-1 adrenergic receptor antagonist. It competitively blocks postsynaptic alpha-1 adrenergic receptors, leading to vasodilation of both arterioles and venules. This results in a reduction in peripheral vascular resistance and a decrease in both systolic and diastolic blood pressure. It also reduces preload and afterload.
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/feces (6-10% unchanged), minor renal excretion (6-10% unchanged)
Unchanged:
6-10%
Pharmacodynamics
OnsetOfAction:
Approximately 30 minutes
PeakEffect:
2-4 hours
DurationOfAction:
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 may lead to lasting sexual problems and impotence.
Other Possible Side Effects
Like all medications, this drug can cause side effects, although many people may not experience any or may only have mild symptoms. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical help:
Feeling dizzy, sleepy, tired, or weak
Headache
* Upset stomach
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor for advice. 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 may lead to lasting sexual problems and impotence.
Other Possible Side Effects
Like all medications, this drug can cause side effects, although many people may not experience any or may only have mild symptoms. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical help:
Feeling dizzy, sleepy, tired, or weak
Headache
* Upset stomach
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor for advice. 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 fainting (especially after the first dose or dose increase)
- Persistent lightheadedness
- Rapid or irregular heartbeat
- Swelling in ankles or feet
- Difficulty breathing
- 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, 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 identify potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken safely with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication, including this one.
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 identify potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken safely with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication, including this one.
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 cessation. Before resuming driving or other tasks, make sure you understand how this medication affects you.
To minimize the risk of dizziness or fainting, stand up slowly when getting up from a sitting or lying down position, and exercise caution when navigating stairs.
As directed by your healthcare provider, regularly monitor your blood pressure.
Be aware that this medication may interfere with certain laboratory tests. 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 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.
Additionally, consult with your doctor before consuming alcohol. In hot weather or during physical activity, be cautious and drink plenty of fluids to prevent dehydration.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. It is crucial 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 cessation. Before resuming driving or other tasks, make sure you understand how this medication affects you.
To minimize the risk of dizziness or fainting, stand up slowly when getting up from a sitting or lying down position, and exercise caution when navigating stairs.
As directed by your healthcare provider, regularly monitor your blood pressure.
Be aware that this medication may interfere with certain laboratory tests. 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 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.
Additionally, consult with your doctor before consuming alcohol. In hot weather or during physical activity, be cautious and drink plenty of fluids to prevent dehydration.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. It is crucial to discuss the potential benefits and risks of this medication to both you and your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension (low blood pressure)
- Drowsiness
- Dizziness
- Syncope (fainting)
- Tachycardia (rapid heart rate)
What to Do:
Call 911 or your local emergency number immediately. For non-emergencies, call Poison Control at 1-800-222-1222. Treatment is supportive, including placing the patient in a supine position, administering fluids, and if necessary, vasopressors.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil): Risk of symptomatic hypotension.
- Other alpha-blockers (e.g., tamsulosin, doxazosin): Increased risk of hypotension.
Moderate Interactions
- Beta-blockers (e.g., propranolol, metoprolol): Additive hypotensive effects.
- Diuretics (e.g., hydrochlorothiazide, furosemide): Additive hypotensive effects.
- Antihypertensive agents (e.g., ACE inhibitors, ARBs, CCBs): Additive hypotensive effects.
- Alcohol: May enhance hypotensive effects.
Minor Interactions
- NSAIDs (e.g., ibuprofen, naproxen): May reduce antihypertensive effect of prazosin.
Monitoring
Baseline Monitoring
Blood Pressure (sitting and standing)
Rationale: To establish baseline and assess for orthostatic hypotension before initiating therapy.
Timing: Prior to initiation of therapy.
Heart Rate
Rationale: To establish baseline.
Timing: Prior to initiation of therapy.
Routine Monitoring
Blood Pressure (sitting and standing)
Frequency: Regularly, especially during dose titration and periodically thereafter.
Target: Individualized based on treatment goals (e.g., <130/80 mmHg for most adults).
Action Threshold: Significant orthostatic drop (>20 mmHg systolic or >10 mmHg diastolic) or symptomatic hypotension.
Heart Rate
Frequency: Regularly, especially during dose titration.
Target: 60-100 bpm (unless otherwise indicated).
Action Threshold: Significant bradycardia or tachycardia.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Fainting (syncope)
- Palpitations
- Headache
- Nausea
- Weakness
- Fatigue
- Nasal congestion
- Edema
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.
Lactation
Prazosin is excreted in small amounts into breast milk. The American Academy of Pediatrics considers it compatible with breastfeeding. Monitor breastfed infants for signs of hypotension or drowsiness.
Infant Risk:
Low risk; monitor for drowsiness or hypotension.
Pediatric Use
Safety and effectiveness in pediatric patients for hypertension have not been established. Off-label use for PTSD-related nightmares is reported, but dosing should be carefully titrated by a specialist.
Geriatric Use
Geriatric patients may be more sensitive to the hypotensive effects of prazosin, particularly the 'first-dose phenomenon'. A lower initial dose and slower titration are recommended. Monitor closely for orthostatic hypotension.
Clinical Information
Clinical Pearls
- The 'first-dose phenomenon' (marked postural hypotension, occasionally with syncope) can occur within 30-90 minutes of the initial dose or a dose increase. To minimize this, the first dose (and any subsequent dose increases) should be taken at bedtime.
- Advise patients to avoid activities requiring mental alertness for the first few hours after the initial dose or dose increase.
- Prazosin is often used as an add-on therapy for hypertension, not typically as monotherapy.
- Off-label use for PTSD-related nightmares is well-supported by clinical experience and some studies, often leading to significant improvement in sleep quality and nightmare frequency.
Alternative Therapies
- Other alpha-1 adrenergic blockers (e.g., doxazosin, terazosin)
- Thiazide diuretics (e.g., hydrochlorothiazide)
- ACE inhibitors (e.g., lisinopril, enalapril)
- Angiotensin Receptor Blockers (ARBs) (e.g., losartan, valsartan)
- Beta-blockers (e.g., metoprolol, atenolol)
- Calcium Channel Blockers (CCBs) (e.g., amlodipine, nifedipine)
Cost & Coverage
Average Cost:
$10 - $30 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 2 (Generic)
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 medical attention. When seeking help, be prepared to provide details about the medication, including the amount taken and the time it happened, to facilitate prompt and effective treatment.