Doxazosin 8mg 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, 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 to feel better.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding the bathroom. Keep all medications in a safe 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 instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to check if there are 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, 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 to feel better.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding the bathroom. Keep all medications in a safe 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 instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to check if there are 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 new increased doses, at bedtime to minimize the risk of dizziness or fainting.
- Avoid sudden changes in position (e.g., standing up quickly from a sitting or lying position) to prevent dizziness or fainting.
- Avoid activities that require alertness (e.g., driving, operating machinery) for at least 12 hours after the first dose or any dose increase.
- Limit or avoid alcohol consumption, as it can worsen dizziness and lower blood pressure.
- Stay hydrated, especially in hot weather or during exercise, to help prevent low blood pressure.
- Report any prolonged, painful erection (priapism) immediately to your doctor.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
For Hypertension: Initial 1 mg once daily; titrate up to 16 mg once daily. For BPH: Initial 1 mg once daily; titrate up to 8 mg once daily.
Dose Range:
1 - 16 mg
Condition-Specific Dosing:
hypertension:
Initial 1 mg once daily, maximum 16 mg once daily. Dose titration typically occurs at 1-2 week intervals.
benignProstaticHyperplasia:
Initial 1 mg once daily, maximum 8 mg once daily. Dose titration typically occurs at 1-2 week intervals.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No dosage adjustment necessary.
Moderate:
No dosage adjustment necessary.
Severe:
No dosage adjustment necessary.
Dialysis:
Doxazosin is highly protein bound and not dialyzable; no specific adjustment needed beyond standard dosing.
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:
Use with caution; not recommended in severe impairment due to extensive hepatic metabolism and lack of specific studies.
Pharmacology
Mechanism of Action
Doxazosin is a selective alpha-1 adrenergic receptor blocker. It competitively inhibits the binding of norepinephrine to alpha-1 receptors in vascular smooth muscle, leading to vasodilation and a reduction in peripheral vascular resistance, thus lowering 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:
2.8 L/kg
ProteinBinding:
Approximately 98%
CnssPenetration:
Limited
Elimination:
HalfLife:
19-22 hours (mean 22 hours)
Clearance:
Not available (primarily hepatic metabolism)
ExcretionRoute:
Fecal (approximately 63%), Renal (approximately 9%)
Unchanged:
<5% (in urine)
Pharmacodynamics
OnsetOfAction:
Within 1-2 hours (for blood pressure reduction)
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 can occur even when you are not having sex. If left untreated, this may lead to long-term sexual problems and impotence.
Other Possible Side Effects
Like all medications, this drug can cause side effects. However, many people do not experience any side effects or only have mild ones. 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
Reporting Side Effects
This is not an exhaustive list of all possible side effects. If you have questions or concerns about side effects, contact 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 can occur even when you are not having sex. If left untreated, this may lead to long-term sexual problems and impotence.
Other Possible Side Effects
Like all medications, this drug can cause side effects. However, many people do not experience any side effects or only have mild ones. 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
Reporting Side Effects
This is not an exhaustive list of all possible side effects. If you have questions or concerns about side effects, contact 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)
- Chest pain
- Shortness of breath
- Swelling in the ankles or feet
- Persistent or painful erection (priapism)
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 how your body processes the medication.
Additionally, this medication may interact with other medications or health conditions. To ensure safe use, it is crucial to:
Inform your doctor and pharmacist about all the medications you are currently taking, including prescription and over-the-counter (OTC) medications, natural products, and vitamins.
Share information about any health problems you have, as these may impact the safety and effectiveness of the medication.
Verify with your doctor that it is safe to take this medication in combination with your other medications and health conditions.
Do not start, stop, or change the dose of any medication without first consulting your doctor to avoid potential interactions or adverse effects.
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 how your body processes the medication.
Additionally, this medication may interact with other medications or health conditions. To ensure safe use, it is crucial to:
Inform your doctor and pharmacist about all the medications you are currently taking, including prescription and over-the-counter (OTC) medications, natural products, and vitamins.
Share information about any health problems you have, as these may impact the safety and effectiveness of the medication.
Verify with your doctor that it is safe to take this medication in combination with your other medications and health conditions.
Do not start, stop, or change the dose of any medication without first consulting your doctor to avoid potential interactions or adverse effects.
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 operating a vehicle 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. Monitor your blood pressure as directed by your healthcare provider.
If you are scheduled to undergo cataract surgery or any other eye procedure, consult with your doctor beforehand. For individuals taking this medication for an enlarged prostate, follow your doctor's instructions regarding 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 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.
Individuals 70 years or older should use this medication with caution, as they may be more susceptible to side effects. If you are pregnant, plan to become pregnant, or are breastfeeding, consult your doctor to discuss the potential benefits and risks to 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 operating a vehicle 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. Monitor your blood pressure as directed by your healthcare provider.
If you are scheduled to undergo cataract surgery or any other eye procedure, consult with your doctor beforehand. For individuals taking this medication for an enlarged prostate, follow your doctor's instructions regarding 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 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.
Individuals 70 years or older should use this medication with caution, as they may be more susceptible to side effects. If you are pregnant, plan to become pregnant, or are breastfeeding, consult your doctor to discuss the potential benefits and risks to you and your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension (extremely low blood pressure)
- Dizziness
- Fainting
- Tachycardia (rapid heart rate)
What to Do:
In case of overdose, immediately seek emergency medical attention or call Poison Control at 1-800-222-1222. Management involves supporting the cardiovascular system, including placing the patient in a supine position with legs elevated, and administering intravenous fluids and vasopressors if necessary. Dialysis is not effective.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil): Concomitant use can lead to symptomatic hypotension (e.g., dizziness, lightheadedness, syncope). Patients should be stable on alpha-blocker therapy before initiating a PDE5 inhibitor, and PDE5 inhibitors should be started at the lowest dose.
Moderate Interactions
- Other antihypertensive agents (e.g., beta-blockers, calcium channel blockers, diuretics, ACE inhibitors): Additive hypotensive effects may occur, requiring careful monitoring of blood pressure.
- CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin, ritonavir): May increase doxazosin plasma concentrations, potentially increasing hypotensive effects. Monitor for increased adverse effects.
- CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin): May decrease doxazosin plasma concentrations, potentially reducing efficacy. Monitor for reduced therapeutic effect.
Minor Interactions
- NSAIDs: May reduce the antihypertensive effect of doxazosin.
- Estrogens: May cause fluid retention, potentially antagonizing the antihypertensive effect.
Monitoring
Baseline Monitoring
Blood Pressure (sitting and standing)
Rationale: To establish baseline blood pressure and assess for orthostatic hypotension before initiating therapy.
Timing: Prior to first dose and before each dose increase.
Liver Function Tests (LFTs)
Rationale: Doxazosin is extensively metabolized by the liver; baseline assessment is prudent, especially in patients with suspected hepatic impairment.
Timing: Prior to initiation in patients with pre-existing liver conditions or risk factors.
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 hypertension).
Action Threshold: Significant orthostatic drop (>20 mmHg systolic or >10 mmHg diastolic) or symptomatic hypotension warrants dose adjustment or discontinuation.
Symptoms of Orthostatic Hypotension (dizziness, lightheadedness, syncope)
Frequency: Daily, especially during initial therapy and dose increases.
Target: Absence of symptoms.
Action Threshold: Presence of symptoms warrants patient education, dose adjustment, or re-evaluation of therapy.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Syncope (fainting)
- Palpitations
- Fatigue
- Headache
- Nasal congestion
- Peripheral edema
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.
Trimester-Specific Risks:
First Trimester:
Limited human data; animal studies suggest potential for developmental toxicity at high doses.
Second Trimester:
Limited human data; potential for fetal hypotension.
Third Trimester:
Limited human data; potential for fetal/neonatal hypotension.
Lactation
Limited data suggest doxazosin is excreted in human milk in small amounts. Use with caution. The decision to breastfeed should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and the benefits of treatment to the mother.
Infant Risk:
L3 (Limited data; possible risk). Monitor breastfed infants for signs of hypotension (e.g., lethargy, poor feeding).
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Not recommended for use in children.
Geriatric Use
Elderly patients may be more sensitive to the hypotensive effects of doxazosin, particularly orthostatic hypotension. Initiate therapy with the lowest dose and titrate slowly. Monitor blood pressure closely.
Clinical Information
Clinical Pearls
- The 'first-dose phenomenon' (marked postural hypotension, dizziness, or syncope) can occur, especially with the initial dose or dose increases. To mitigate this, administer the first dose and any subsequent dose increases at bedtime.
- Advise patients to avoid situations where injury could result if syncope occurs (e.g., driving, operating machinery) for 12 hours after the initial dose or dose increases.
- Doxazosin is effective for both hypertension and BPH, offering a dual benefit for some patients.
- Extended-release (XL) formulations are available, which may reduce the risk of first-dose phenomenon and improve tolerability due to slower absorption.
- Patients should be educated on the symptoms of orthostatic hypotension and advised to rise slowly from a sitting or lying position.
Alternative Therapies
- Other Alpha-1 Adrenergic Blockers (for BPH and/or Hypertension): Terazosin, Prazosin, Tamsulosin, Alfuzosin, Silodosin.
- For Hypertension: ACE inhibitors, Angiotensin Receptor Blockers (ARBs), Calcium Channel Blockers (CCBs), Thiazide diuretics, Beta-blockers.
- For BPH: 5-alpha reductase inhibitors (e.g., finasteride, dutasteride), Anticholinergics (for overactive bladder symptoms), PDE5 inhibitors (e.g., tadalafil for BPH symptoms).
Cost & Coverage
Average Cost:
Varies widely, typically $10-$50 per 30 tablets (8mg generic)
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 details. 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 information about the medication taken, the amount, and the time it happened.