Doxazosin Dosage

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Usual Adult Dose for:

Usual Geriatric Dose for:

Additional dosage information:

Usual Adult Dose for Hypertension

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

Usual Adult Dose for Benign Prostatic Hyperplasia

Initial dose:
Immediate-release: 1 mg orally once a day.
Extended-release: 4 mg orally once a day with breakfast

Maintenance dose:
Immediate-release: 1 to 8 mg orally once a day.
Extended-release: 4 to 8 mg orally once a day with breakfast. Depending on the patient's symptomatic response and tolerability, the dose may be increased to 8 mg (the maximum recommended dose). The recommended titration interval is 3 to 4 weeks.

If switching from immediate-release doxazosin to doxazosin extended-release tablets, therapy should be initiated with the lowest dose (4 mg once daily). Prior to starting therapy with doxazosin extended-release tablets, the final evening dose of immediate-release doxazosin should not be taken. If doxazosin extended-release is discontinued for several days, therapy should be restarted using the 4 mg once daily dose.

Usual Geriatric Dose for Hypertension

Initial dose: 0.5 mg orally once a day.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Doxazosin should be used with caution in patients with hepatic impairment.

The extended-release form of doxazosin is not recommended for use in BPH patients with severe liver impairment.

Dose Adjustments

Depending on the individual patient's standing blood pressure response (based on measurements taken at 2 to 6 hours postdose and 24 hours post- dose), dosage of the immediate-release preparations may then be increased to 2 mg and thereafter if necessary to 4 mg, 8 mg and 16 mg to achieve the desired reduction in blood pressure. Depending on the individual patient's urodynamics and BPH symptomatology, dosage may be increased to 2 mg and thereafter to 4 mg and 8 mg once daily. The recommended titration interval for immediate-release formulations is 1 to 2 weeks.

Precautions

Use of doxazosin in patients with altered liver function should be undertaken with particular caution, if at all, as excretion is almost wholly hepatic.

Postural effects are most likely to occur 2 to 6 hours after a dose. Therefore blood pressure measurements should be taken during this time period after the first dose and with each increase in dose. Increases in dose beyond 4 mg increase the likelihood of excessive postural effects including syncope, postural dizziness/vertigo and postural hypotension.

Safety and effectiveness have not been established in pediatric patients (less than 18 years of age).

Dialysis

Doxazosin is not dialyzable as it is highly protein bound.

Other Comments

The maximum recommended dose for BPH is 8 mg once a day. If doxazosin administration is discontinued for several days, therapy should be restarted using the initial dosing regimen.

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