Doxazosin Dosage

Medically reviewed by Drugs.com. Last updated on Mar 17, 2023.

Applies to the following strengths: 4 mg; 8 mg; 1 mg; 2 mg

Usual Adult Dose for:

Hypertension
Benign Prostatic Hyperplasia

Additional dosage information:

Renal Dose Adjustments
Liver Dose Adjustments
Dose Adjustments
Precautions
Dialysis
Other Comments

Usual Adult Dose for Hypertension

Immediate release:
Initial dose: 1 mg orally once a day
Maintenance dose: 1 to 16 mg orally once a day

Comments: Dosage may be doubled up to 16 mg once a day as needed to achieve desired blood pressure reduction.

Usual Adult Dose for Benign Prostatic Hyperplasia

Initial dose:

Immediate release: 1 mg orally once a day in the morning or evening
Extended release: 4 mg orally once a day with breakfast

Maintenance dose:

Immediate release: 1 to 8 mg orally once a day in the morning or evening
Extended release: 4 to 8 mg orally once a day with breakfast

Maximum dose: 8 mg orally once a day

Comments: Depending on the patient's urodynamics, symptomatic response, and tolerability, the dose may be doubled after 1 to 2 weeks (immediate release) or 3 to 4 weeks (extended release) at the previous dose.

Use: Treatment of signs and symptoms of benign prostatic hyperplasia (BPH).

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Mild to moderate liver dysfunction (Child-Pugh A or B): Use with caution
Severe liver dysfunction (Child-Pugh C): Not recommended

Dose Adjustments

Conversion from immediate release to extended release:

Skip the final evening dose of the immediate release formulation and initiate the extended release formulation at the lowest dose (4 mg once a day).

Coadministration with phosphodiesterase-5 (PDE-5) inhibitors:

Extended release: Initiate treatment at the lowest dose.

Precautions

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available

Other Comments

Administration advice:

If this drug is discontinued for several days, therapy should be restarted using the initial dosing regimen.
Extended release: Tablets should be swallowed whole; do not chew, crush, cut, or divide tablets.

Monitoring:

Cardiovascular: Blood pressure (for at least 6 hours after the initial dose and each dose increase and routinely thereafter)

Patient advice:

Advise patients how to avoid symptoms of postural hypotension and what to do if they occur. Also, encourage patients to avoid situations where injury could result if these symptoms occur.
Inform male patients about the seriousness of priapism and instruct them to seek immediate medical attention if it occurs.
Advise patients to report current or previous use of this drug to their ophthalmologist.
Extended release formulations may contain a nonabsorbable coating designed to control drug release over time. Advise patients not to be concerned if they notice tablet remains in their stools.