Prazosin Hcl 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 is also sometimes used off-label to help with nightmares, especially those 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. Take your medication as directed, with or without food. It's essential to continue taking this medication as prescribed by your doctor or healthcare provider, even if you're feeling well.
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. You may also want to explore 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. Take your medication as directed, with or without food. It's essential to continue taking this medication as prescribed by your doctor or healthcare provider, even if you're feeling well.
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. You may also want to explore 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 alcohol, as it can increase the blood pressure-lowering effect and dizziness.
- Maintain adequate hydration.
- Follow a low-sodium diet and exercise regularly as advised by your doctor for blood pressure control.
- Be cautious when driving or operating machinery until you know how the medication affects you.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Hypertension: Initial 1 mg orally 2-3 times daily. Maintenance 6-15 mg/day in divided doses. PTSD-related nightmares (off-label): Initial 1 mg orally at bedtime, titrate up to 10-15 mg at bedtime.
Dose Range:
1 - 20 mg
Condition-Specific Dosing:
hypertension:
Initial 1 mg orally 2-3 times daily. Maintenance 6-15 mg/day in divided doses. Max 20 mg/day.
ptsd_nightmares_off_label:
Initial 1 mg orally at bedtime, titrate up to 10-15 mg at bedtime, based on response and tolerability.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established for hypertension. Limited data for PTSD-related nightmares (off-label, typically 1-5 mg at bedtime, titrated).
Adolescent:
Not established for hypertension. Limited data for PTSD-related nightmares (off-label, typically 1-5 mg at bedtime, titrated).
Dose Adjustments
Renal Impairment:
Mild:
No specific dose adjustment required, but monitor response.
Moderate:
No specific dose adjustment required, but monitor response. Consider lower initial dose.
Severe:
No specific dose adjustment required, but monitor response. Consider lower initial dose and slower titration.
Dialysis:
Prazosin is not dialyzable. No specific supplemental dose needed, but monitor for exaggerated hypotensive response.
Hepatic Impairment:
Mild:
Use with caution, monitor for increased effects.
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 reduces peripheral vascular resistance and venous return to the heart, resulting in a decrease in both systolic and diastolic blood pressure. It does not affect presynaptic alpha-2 receptors, thus avoiding reflex tachycardia seen with non-selective alpha-blockers.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 60%
Tmax:
1-3 hours
FoodEffect:
Food may delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
Approximately 0.5 L/kg
ProteinBinding:
Approximately 95%
CnssPenetration:
Limited
Elimination:
HalfLife:
2-3 hours
Clearance:
Not readily available (primarily hepatic metabolism)
ExcretionRoute:
Primarily bile/feces (60-90%), minor renal excretion (6-10%)
Unchanged:
Approximately 6-10% (renal excretion)
Pharmacodynamics
OnsetOfAction:
30-60 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, including:
+ 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 side effects or only have mild 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:
Feeling dizzy, sleepy, tired, or weak
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, including:
+ 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 side effects or only have mild 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:
Feeling dizzy, sleepy, tired, or weak
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 fainting (especially with the first dose or dose increase)
- Persistent lightheadedness
- Rapid or irregular heartbeat
- Chest pain
- Difficulty breathing
- Swelling of ankles or feet
- 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 allergic reaction you experienced, including any symptoms that occurred.
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 assess potential interactions between this medication and other substances you are taking.
* Any existing health problems, as this medication may interact with certain conditions or exacerbate underlying health issues.
To ensure your safety, it is crucial to verify that this medication can be taken safely with all your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting 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 allergic reaction you experienced, including any symptoms that occurred.
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 assess potential interactions between this medication and other substances you are taking.
* Any existing health problems, as this medication may interact with certain conditions or exacerbate underlying health issues.
To ensure your safety, it is crucial to verify that this medication can be taken safely with all your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
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 operate a vehicle or engage in any activity that requires your full attention 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, stand up slowly after sitting or lying down, and exercise caution 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 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 them with your doctor.
Additionally, 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, plan 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.
After taking your first dose, or if your dose is increased, or if you restart this medication after stopping it, do not operate a vehicle or engage in any activity that requires your full attention 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, stand up slowly after sitting or lying down, and exercise caution 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 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 them with your doctor.
Additionally, 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, plan 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 (low blood pressure)
- Drowsiness
- Dizziness
- Syncope (fainting)
- Tachycardia (rapid heart rate)
- Shock
What to Do:
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 patient in a supine position.
Drug Interactions
Major Interactions
- PDE5 Inhibitors (e.g., sildenafil, tadalafil, vardenafil): Risk of severe hypotension and syncope due to additive vasodilatory effects. Concomitant use is generally not recommended, or use with extreme caution and dose adjustment.
Moderate Interactions
- Other Antihypertensives (e.g., beta-blockers, ACE inhibitors, diuretics): Additive hypotensive effects. Monitor blood pressure closely.
- Alcohol: May enhance hypotensive effects.
- NSAIDs (e.g., ibuprofen, naproxen): May reduce the antihypertensive effect of prazosin.
- Alpha-adrenergic agonists (e.g., pseudoephedrine, phenylephrine): May antagonize the hypotensive effect of prazosin.
- Beta-blockers: May increase the risk of first-dose syncope.
Monitoring
Baseline Monitoring
Blood Pressure (BP)
Rationale: To establish baseline and assess the need for treatment.
Timing: Prior to initiation of therapy.
Heart Rate (HR)
Rationale: To establish baseline.
Timing: Prior to initiation of therapy.
Orthostatic Blood Pressure (BP)
Rationale: To assess for baseline orthostatic changes and risk of first-dose syncope.
Timing: Prior to initiation of therapy.
Routine Monitoring
Blood Pressure (BP)
Frequency: Regularly, especially during dose titration and periodically thereafter.
Target: Individualized, typically <130/80 mmHg for hypertension.
Action Threshold: Persistent hypotension, or inadequate BP control requiring dose adjustment.
Heart Rate (HR)
Frequency: Regularly, especially during dose titration and periodically thereafter.
Target: 60-100 bpm (unless otherwise indicated)
Action Threshold: Significant bradycardia or tachycardia.
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 patient education or dose adjustment.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Palpitations
- Syncope (fainting)
- Nasal congestion
- Headache
- Drowsiness
- Fatigue
- Nausea
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, but caution is advised. Monitor the infant for signs of hypotension (e.g., lethargy, poor feeding).
Infant Risk:
Low to moderate risk (L3). Monitor for sedation, poor feeding, or hypotension.
Pediatric Use
Safety and efficacy for hypertension in pediatric patients have not been established. Use for PTSD-related nightmares is off-label and based on limited clinical experience; dosing should be individualized and carefully titrated.
Geriatric Use
Elderly patients may be more sensitive to the hypotensive effects of prazosin, particularly orthostatic hypotension. Initiate therapy with lower doses (e.g., 0.5 mg) and titrate slowly. Monitor blood pressure and symptoms closely.
Clinical Information
Clinical Pearls
- **First-Dose Syncope:** A significant risk, especially with the initial dose or dose increases. Advise patients to take the first dose at bedtime and avoid activities requiring alertness for 12-24 hours.
- **Orthostatic Hypotension:** Common side effect. Educate patients on slow position changes.
- **Off-label use for PTSD Nightmares:** Prazosin is increasingly used for PTSD-related nightmares and sleep disturbances, often at higher doses than for hypertension. This use is well-supported by clinical experience and some studies.
- **Tolerance:** Tolerance to the antihypertensive effect may develop over time, requiring dose adjustment.
- **Nasal Congestion:** A common side effect due to alpha-1 blockade in nasal vasculature.
Alternative Therapies
- Other Alpha-1 Adrenergic Blockers (e.g., terazosin, doxazosin, alfuzosin, tamsulosin)
- Other Antihypertensive Classes (e.g., ACE inhibitors, ARBs, calcium channel blockers, beta-blockers, diuretics)
- For PTSD-related nightmares: Clonidine, mirtazapine, tricyclic antidepressants, psychotherapy (e.g., CBT, EMDR).
Cost & Coverage
Average Cost:
$10 - $50 per 30 capsules (5mg)
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 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 it is a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, do not 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 details about the overdose, including the medication taken, the amount, and the time it occurred.