Doxazosin 4mg Tablets
It is used to treat the signs of an enlarged prostate.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
Dec 1989
DEA Schedule
Not Controlled
Overview
What is this medicine?
Doxazosin is a medication used to treat high blood pressure and symptoms of an enlarged prostate (BPH). It works by relaxing blood vessels, which lowers blood pressure, and by relaxing muscles in the prostate and bladder, which helps urine flow more easily.
How to Use This Medicine
Taking Your Medication Correctly
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. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start feeling better.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, 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 specifically instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to inquire about drug take-back programs available in your area.
What to Do If You Miss 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. If you miss taking your medication for several days in a row, contact your doctor before restarting your medication regimen.
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. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start feeling better.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, 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 specifically instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to inquire about drug take-back programs available in your area.
What to Do If You Miss 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. If you miss taking your medication for several days in a row, contact your doctor before restarting your medication regimen.
Lifestyle & Tips
- Take the first dose and any dose increases at bedtime to minimize the 'first-dose phenomenon' (sudden drop in blood pressure).
- Avoid sudden changes in position (e.g., standing up quickly from a sitting or lying position) to prevent dizziness or fainting.
- Be cautious when driving or operating machinery, especially at the start of treatment or after dose increases, until you know how the medication affects you.
- Limit or avoid alcohol consumption, as it can worsen dizziness and low blood pressure.
- Stay hydrated, especially in hot weather or during exercise, to help prevent low blood pressure.
- Inform your doctor or dentist that you are taking doxazosin before any surgery or dental procedures, especially cataract surgery (risk of Intraoperative Floppy Iris Syndrome).
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
4 mg once daily (for hypertension or BPH, after titration)
Dose Range:
1 - 16 mg
Condition-Specific Dosing:
hypertension:
Initial: 1 mg once daily; titrate up to 16 mg once daily based on response and tolerability. Common maintenance: 2-8 mg once daily.
bph:
Initial: 1 mg once daily; titrate up to 8 mg once daily based on response and tolerability. Common maintenance: 2-8 mg once daily.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established (Safety and efficacy not established for hypertension or BPH)
Adolescent:
Not established (Safety and efficacy not established for hypertension or BPH)
Dose Adjustments
Renal Impairment:
Mild:
No dosage adjustment needed.
Moderate:
No dosage adjustment needed.
Severe:
No dosage adjustment needed.
Dialysis:
Doxazosin is highly protein bound and not dialyzable; no specific adjustment needed.
Hepatic Impairment:
Mild:
Use with caution; consider lower initial dose and slower titration.
Moderate:
Use with caution; consider lower initial dose and slower titration. Monitor closely for adverse effects.
Severe:
Not well studied; use with extreme caution or avoid. Doxazosin is extensively metabolized by the liver.
Pharmacology
Mechanism of Action
Doxazosin is a selective alpha-1 adrenergic receptor blocker. It causes vasodilation by blocking alpha-1 receptors in peripheral arterioles, leading to a reduction in peripheral vascular resistance and blood pressure. In benign prostatic hyperplasia (BPH), it relaxes the smooth muscle in the prostate and bladder neck, reducing bladder outlet obstruction and improving urine flow.
Pharmacokinetics
Absorption:
Bioavailability:
62-69%
Tmax:
2-3 hours
FoodEffect:
Minimal effect on absorption.
Distribution:
Vd:
1.6 L/kg
ProteinBinding:
Approximately 98%
CnssPenetration:
Limited
Elimination:
HalfLife:
19-22 hours
Clearance:
Not available
ExcretionRoute:
Feces (63%), Urine (9%)
Unchanged:
<5% (in urine)
Pharmacodynamics
OnsetOfAction:
1-2 hours (for blood pressure lowering)
PeakEffect:
2-6 hours
DurationOfAction:
24 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while 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
New or worsening chest pain
Shortness of breath
Swelling in the arms or legs
A painful erection (hard penis) or an erection that lasts longer than 4 hours, which may occur even when you are not having sex. If left untreated, this can lead to lasting sexual problems and impotence.
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:
Feeling dizzy, sleepy, tired, or weak
Headache
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.
Although rare, some people may experience severe and potentially life-threatening side effects while 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
New or worsening chest pain
Shortness of breath
Swelling in the arms or legs
A painful erection (hard penis) or an erection that lasts longer than 4 hours, which may occur even when you are not having sex. If left untreated, this can lead to lasting sexual problems and impotence.
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:
Feeling dizzy, sleepy, tired, or weak
Headache
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, especially when standing up
- Fainting (syncope)
- Palpitations or rapid heartbeat
- Chest pain
- Swelling in ankles or feet
- Priapism (a painful erection lasting more than 4 hours â seek immediate medical attention)
- Severe allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
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.
If you have liver disease, as this may affect the safety and efficacy of the medication.
To ensure safe treatment, it is crucial to disclose all of your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
Vitamins
Additionally, inform your doctor about any existing health problems. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances or health conditions.
Remember to always consult with your doctor before:
Starting any new medication
Stopping a medication
Changing the dosage of a medication
This will help prevent potential adverse interactions and ensure your safety while taking this 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.
If you have liver disease, as this may affect the safety and efficacy of the medication.
To ensure safe treatment, it is crucial to disclose all of your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
Vitamins
Additionally, inform your doctor about any existing health problems. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances or health conditions.
Remember to always consult with your doctor before:
Starting any new medication
Stopping a medication
Changing the dosage of a medication
This will help prevent potential adverse interactions and ensure your safety while taking this medication.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
When starting this medication, or after any dose increase, or if you restart it after stopping, avoid driving or engaging in activities that require alertness for 24 hours. Before driving or performing other tasks, ensure 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.
Follow your doctor's instructions for monitoring your blood pressure.
If you are scheduled for cataract surgery or any other eye procedure, consult with your doctor beforehand.
For individuals taking this medication for an enlarged prostate, adhere to your doctor's recommendations for regular rectal exams to check the prostate gland and blood tests, including the prostate-specific antigen (PSA) test.
If you have high blood pressure and are taking this medication, discuss with your doctor 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, and certain natural products or aids.
If you are 70 years old or older, use this medication with caution, as you may be more susceptible to side effects.
Inform your doctor if you are pregnant, plan to become pregnant, or are breastfeeding, as you will need to discuss the potential benefits and risks to both you and your baby.
When starting this medication, or after any dose increase, or if you restart it after stopping, avoid driving or engaging in activities that require alertness for 24 hours. Before driving or performing other tasks, ensure 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.
Follow your doctor's instructions for monitoring your blood pressure.
If you are scheduled for cataract surgery or any other eye procedure, consult with your doctor beforehand.
For individuals taking this medication for an enlarged prostate, adhere to your doctor's recommendations for regular rectal exams to check the prostate gland and blood tests, including the prostate-specific antigen (PSA) test.
If you have high blood pressure and are taking this medication, discuss with your doctor 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, and certain natural products or aids.
If you are 70 years old or older, use this medication with caution, as you may be more susceptible to side effects.
Inform your doctor if you are pregnant, plan to become pregnant, or are breastfeeding, as you will need to discuss the potential benefits and risks to both you and your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension (very low blood pressure)
- Dizziness
- Fainting (syncope)
- Tachycardia (rapid heart rate)
What to Do:
In case of suspected overdose, seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Management typically involves placing the patient in a supine position with legs elevated to restore blood pressure. If this is insufficient, vasopressors may be administered. Volume expanders may also be considered. Doxazosin is highly protein bound and not dialyzable.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil, avanafil): Concomitant use can lead to symptomatic hypotension due to additive vasodilatory effects. If co-administration is necessary, patients should be stable on alpha-blocker therapy before initiating a PDE5 inhibitor at the lowest dose.
- Other alpha-blockers (e.g., prazosin, terazosin, tamsulosin): Additive hypotensive effects.
Moderate Interactions
- Antihypertensive agents (e.g., ACE inhibitors, ARBs, beta-blockers, diuretics, calcium channel blockers): Additive hypotensive effects; monitor blood pressure closely.
- CYP3A4 inhibitors (strong, e.g., ketoconazole, clarithromycin, ritonavir): May increase doxazosin plasma concentrations, increasing risk of adverse effects. Monitor for hypotension.
- Beta-blockers: Increased risk of first-dose syncope when initiating doxazosin in patients on beta-blockers.
Minor Interactions
- Alcohol: May enhance hypotensive effects.
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 and before each dose increase.
Renal Function (SCr, BUN)
Rationale: To assess baseline kidney function, though no dose adjustment is typically needed for renal impairment.
Timing: Prior to initiation.
Liver Function Tests (ALT, AST, bilirubin)
Rationale: To assess baseline liver function, especially if hepatic impairment is suspected, as doxazosin is extensively metabolized by the liver.
Timing: Prior to initiation, if clinically indicated.
Routine Monitoring
Blood Pressure (sitting and standing)
Frequency: Regularly, especially during dose titration and periodically thereafter.
Target: Individualized target blood pressure (e.g., <130/80 mmHg for hypertension); minimal orthostatic drop.
Action Threshold: Significant orthostatic hypotension (e.g., >20 mmHg systolic or >10 mmHg diastolic drop) or symptomatic hypotension; consider dose reduction or discontinuation.
Symptoms of Orthostatic Hypotension
Frequency: Daily, especially during initial therapy and dose increases.
Target: Absence of dizziness, lightheadedness, syncope.
Action Threshold: Recurrent or severe symptoms; consider dose reduction or discontinuation.
BPH Symptom Score (e.g., AUA Symptom Score)
Frequency: Periodically, to assess efficacy for BPH.
Target: Improvement in urinary symptoms.
Action Threshold: Lack of improvement or worsening symptoms; consider alternative therapy.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Fainting (syncope)
- Palpitations
- Headache
- Fatigue
- Nasal congestion
- Priapism (prolonged, painful erection)
Special Patient Groups
Pregnancy
Category C. Doxazosin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects at high doses, 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, but human data are limited.
Second Trimester:
Potential for fetal harm based on animal data, but human data are limited.
Third Trimester:
Potential for fetal harm based on animal data, but human data are limited. Alpha-blockers may theoretically affect fetal blood pressure.
Lactation
L3 (Moderately Safe). Limited data suggest doxazosin is excreted into human milk in small amounts. The clinical significance of this is unknown. Monitor breastfed infants for signs of hypotension (e.g., lethargy, poor feeding). Use with caution.
Infant Risk:
Low risk of adverse effects in breastfed infants, but monitor for drowsiness or hypotensive effects.
Pediatric Use
Safety and efficacy have not been established in pediatric patients for either hypertension or BPH. Not recommended for routine use in this population.
Geriatric Use
Geriatric patients may be more susceptible to the hypotensive effects of doxazosin, particularly orthostatic hypotension and syncope. Start with the lowest dose (1 mg) and titrate slowly, monitoring blood pressure closely, especially standing blood pressure.
Clinical Information
Clinical Pearls
- The 'first-dose phenomenon' (marked postural hypotension, sometimes with syncope) is a known risk, especially with the initial dose or dose increases. To mitigate this, advise patients to take the first dose and any dose increases at bedtime.
- Doxazosin is effective for both hypertension and BPH, offering a dual benefit for men with both conditions.
- Patients should be warned about the rare but serious adverse effect of priapism (prolonged, painful erection) and instructed to seek immediate medical attention if it occurs.
- Caution is advised when co-administering with PDE5 inhibitors due to the risk of severe hypotension. Patients should be stable on doxazosin before initiating a PDE5 inhibitor at the lowest dose.
- Intraoperative Floppy Iris Syndrome (IFIS) has been observed during cataract surgery in some patients on alpha-1 blockers. Inform the ophthalmologist prior to surgery.
Alternative Therapies
- Other alpha-1 blockers (e.g., terazosin, prazosin, tamsulosin, alfuzosin, silodosin)
- For Hypertension: ACE inhibitors, Angiotensin Receptor Blockers (ARBs), Calcium Channel Blockers (CCBs), Diuretics, Beta-blockers.
- For BPH: 5-alpha reductase inhibitors (e.g., finasteride, dutasteride), Anticholinergics (for overactive bladder symptoms), Beta-3 adrenergic agonists (e.g., mirabegron), minimally invasive procedures, surgery (e.g., TURP).
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets (generic 4mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (for 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 this 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, including the amount taken and the time it happened, to facilitate prompt and effective treatment.