Doxazosin 2mg 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
C
FDA Approved
Dec 1990
DEA Schedule
Not Controlled
Overview
What is this medicine?
Doxazosin is a medication that helps relax blood vessels, which lowers blood pressure. It also relaxes muscles in the prostate and bladder, making it easier to urinate for men with an enlarged prostate. It's often taken once a day.
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 and 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 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 any 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 and 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 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 any 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 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.
- Avoid activities requiring mental alertness for the first 12-24 hours after the initial dose or dose increase.
- Limit alcohol intake, as it can worsen dizziness and low blood pressure.
- Stay hydrated, especially in hot weather or during exercise.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Hypertension: Initial 1 mg once daily, titrated up to 16 mg once daily. BPH: Initial 1 mg once daily, titrated up to 8 mg once daily.
Dose Range:
1 - 16 mg
Condition-Specific Dosing:
hypertension:
Initial 1 mg once daily, titrate to 2 mg, 4 mg, 8 mg, and 16 mg once daily at 1-2 week intervals based on response and tolerability.
bph:
Initial 1 mg once daily, titrate to 2 mg, 4 mg, and 8 mg once daily at 1-2 week intervals based on response and tolerability.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No dose adjustment typically needed.
Moderate:
No dose adjustment typically needed.
Severe:
No dose adjustment typically needed.
Dialysis:
Doxazosin is highly protein bound and not dialyzable. No specific adjustment 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. Monitor closely for adverse effects.
Severe:
Not recommended due to lack of data and potential for increased exposure.
Pharmacology
Mechanism of Action
Doxazosin is a selective alpha-1 adrenergic receptor blocker. It competitively inhibits the binding of norepinephrine and epinephrine to alpha-1 adrenergic receptors on 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:
1.6 L/kg
ProteinBinding:
Approximately 98%
CnssPenetration:
Limited
Elimination:
HalfLife:
22 hours (range 19-24 hours)
Clearance:
Not available
ExcretionRoute:
Fecal (63%), Renal (9%)
Unchanged:
Less than 5% (renal)
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 (priapism) or an erection that lasts longer than 4 hours, which can occur even when 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. 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:
Dizziness
Drowsiness
Fatigue
Weakness
* Headache
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 (priapism) or an erection that lasts longer than 4 hours, which can occur even when 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. 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:
Dizziness
Drowsiness
Fatigue
Weakness
* Headache
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 or loss of consciousness.
- Persistent headache.
- Chest pain or palpitations.
- Swelling in the ankles or feet.
- Priapism (prolonged, painful 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. Be sure to describe the symptoms you experienced as a result of the allergy.
If you have liver disease, as this may affect the use of this medication.
To ensure safe use, it is crucial to discuss the following with your doctor and pharmacist:
All medications you are currently taking, including prescription and over-the-counter drugs, natural products, and vitamins.
Any existing health problems, as this medication may interact with other drugs or health conditions.
Before making any changes to your medication regimen, consult with your doctor to confirm that it is safe to:
Start taking this medication
Stop taking this medication
* Change the dosage of this medication or any other medication you are taking.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the symptoms you experienced as a result of the allergy.
If you have liver disease, as this may affect the use of this medication.
To ensure safe use, it is crucial to discuss the following with your doctor and pharmacist:
All medications you are currently taking, including prescription and over-the-counter drugs, natural products, and vitamins.
Any existing health problems, as this medication may interact with other drugs or health conditions.
Before making any changes to your medication regimen, consult with your doctor to confirm that it is safe to:
Start taking this medication
Stop taking this medication
* Change the dosage of this medication or any other medication you are taking.
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 your initial dose, as well as after any dose increase or when restarting the medication after a period of discontinuation. Before operating a vehicle or performing tasks that demand attention, 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 seated or lying position, and exercise caution when navigating stairs.
As directed by your healthcare provider, regularly monitor your blood pressure.
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, it is crucial to follow your doctor's recommendations 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 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.
Individuals aged 70 years or older should exercise caution when using this medication, as they may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is essential to discuss the benefits and risks of this medication with your doctor to make an informed decision regarding your health and the health of your baby.
To ensure your safety, avoid driving or engaging in activities that require alertness for 24 hours after your initial dose, as well as after any dose increase or when restarting the medication after a period of discontinuation. Before operating a vehicle or performing tasks that demand attention, 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 seated or lying position, and exercise caution when navigating stairs.
As directed by your healthcare provider, regularly monitor your blood pressure.
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, it is crucial to follow your doctor's recommendations 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 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.
Individuals aged 70 years or older should exercise caution when using this medication, as they may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is essential to discuss the benefits and risks of this medication with your doctor to make an informed decision regarding your health and the health of your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension (very low blood pressure)
- Dizziness
- Fainting
- Tachycardia (rapid heart rate)
What to Do:
Call 911 or your local emergency number immediately. Management is primarily supportive, including placing the patient in a supine position with legs elevated, and administering intravenous fluids and vasopressors if needed. Call 1-800-222-1222 for Poison Control.
Drug Interactions
Major Interactions
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil): Risk of symptomatic hypotension. Administer PDE5 inhibitors at least 4-6 hours after doxazosin dose.
Moderate Interactions
- Other antihypertensives (e.g., beta-blockers, diuretics, ACE inhibitors): Additive hypotensive effects.
- Alpha-adrenergic agonists (e.g., pseudoephedrine, phenylephrine): May antagonize the hypotensive effect of doxazosin.
- CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin, ritonavir): May increase doxazosin exposure, increasing risk of hypotension.
- General anesthetics: May enhance hypotensive effects.
Minor Interactions
- NSAIDs: May reduce the antihypertensive effect of doxazosin.
Monitoring
Baseline Monitoring
Blood Pressure (sitting and standing)
Rationale: To establish baseline and assess for orthostatic hypotension, especially with the first dose.
Timing: Prior to initiation of therapy.
Symptoms of BPH (if applicable)
Rationale: To establish baseline and monitor treatment efficacy.
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 hypertension).
Action Threshold: Significant orthostatic drop (>20 mmHg systolic or >10 mmHg diastolic) or symptomatic hypotension.
Symptoms of BPH (e.g., AUA symptom score)
Frequency: Periodically, especially during dose titration.
Target: Improvement in symptom score.
Action Threshold: Lack of improvement or worsening symptoms.
Symptoms of orthostatic hypotension (dizziness, lightheadedness, syncope)
Frequency: Daily, especially during the first few weeks of therapy and with dose increases.
Target: Absence of symptoms.
Action Threshold: Presence of symptoms, requiring dose adjustment or discontinuation.
Symptom Monitoring
- Dizziness
- Lightheadedness
- Fainting (syncope)
- Palpitations
- Headache
- Fatigue
- Nasal congestion
- Peripheral edema
Special Patient Groups
Pregnancy
Category C. Use 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 developmental toxicity observed in animal studies.
Second Trimester:
Limited human data, animal data suggest potential risk.
Third Trimester:
Limited human data, animal data suggest potential risk.
Lactation
L3 (Moderately Safe). Doxazosin is excreted in human milk in small amounts. The effects on the breastfed infant are unknown. Use with caution; monitor infant for drowsiness or hypotension.
Infant Risk:
Low to moderate risk. Monitor for drowsiness, poor feeding, or signs of hypotension.
Pediatric Use
Safety and effectiveness have not been established in pediatric patients. Not recommended for use in this population.
Geriatric Use
Use with caution in elderly patients due to increased sensitivity to hypotensive effects and a higher risk of falls. Consider lower initial doses and slower titration. Monitor closely for orthostatic hypotension.
Clinical Information
Clinical Pearls
- The 'first-dose phenomenon' (marked hypotension, especially orthostatic, and syncope) can occur within 30-90 minutes of the initial dose or a dose increase. To mitigate this, administer the first dose and any subsequent dose increases at bedtime.
- Patients should be advised to avoid situations where injury could result if syncope occurs (e.g., driving, operating machinery) for the first 12-24 hours after the initial dose or dose increase.
- Doxazosin is effective for both hypertension and BPH, offering a dual benefit for men with both conditions.
- Intraoperative Floppy Iris Syndrome (IFIS) has been observed during cataract surgery in some patients on or previously treated with alpha-1 blockers. Inform ophthalmologists of doxazosin use.
- Titration is crucial to minimize adverse effects. Do not increase the dose more frequently than every 1-2 weeks.
Alternative Therapies
- Other alpha-1 blockers (e.g., prazosin, terazosin, tamsulosin, alfuzosin, silodosin)
- Other antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers, calcium channel blockers, diuretics)
- 5-alpha reductase inhibitors (e.g., finasteride, dutasteride for BPH)
- PDE5 inhibitors (e.g., tadalafil for BPH)
- Combination therapy for BPH (e.g., alpha-blocker + 5-alpha reductase inhibitor)
Cost & Coverage
Average Cost:
Price range varies, typically $10-$50 per 30 tablets (2mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (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 consult with your pharmacist. If you have any questions or concerns about this 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 detailed information about the overdose, including the medication taken, the amount, and the time it occurred.