Doxazosin

Indications

Doxazosin is used for: Hypertension, Benign Prostatic Hyperplasia

Adult Dose

Oral Hypertension Adult: Initially, 1 mg at bedtime, may be doubled at 1-2 wk intervals according to response. Maintenance: Up to 4 mg once daily. Max: 16 mg/day. Extended-release: Initially, 4 mg once daily, may increase to max 8 mg once daily after 4 wk. Benign prostatic hyperplasia Adult: Initially, 1 mg at bedtime, may be doubled at 1-2 wk intervals according to response. Maintenance: 2-4 mg/day. Max: 8 mg/day. Extended-release: Initially, 4 mg once daily, may increase to max 8 mg once daily after 4 wk. Hepatic impairment: Use with caution in mild-to-moderate hepatic dysfunction; do not use in severe impairment

Child Dose

Renal Dose

Administration

May be taken with or without food. Give first dose and increase at bedtime to avoid syncope

Contra Indications

Patient w/ history of orthostatic hypotension; benign prostatic hyperplasia and concomitant congestion of the upper urinary tract, chronic urinary tract infection or bladder stones; monotherapy in patients w/ either overflow bladder or anuria w/ or w/o progressive renal insufficiency.

Precautions

Prostatic carcinoma should be ruled out before starting therapy. Hepatic impairment. Pregnancy and lactation. Patient Counselling May impair ability to drive and operate machinery. Monitoring Parameters Monitor BP and renal function. Lactation: Unknown whether drug is excreted in milk; use with caution

Pregnancy-Lactation

Pregnancy Not indicated for use in females or for the treatment of hypertension; the limited available data in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage; no adverse developmental outcomes were observed in animal reproduction studies with oral administration to pregnant rats and rabbits at doses of up to 10 and 4 times, respectively, the 12 mg/day recommended dose; postnatal development was delayed in rats at a dose of 8 times the 12 mg/day recommended dose Lactation Present in human milk; there is no information on effects on breastfed infant or effects on milk production

Interactions

Concomitant admin w/ phosphodiesterase type 5 (PDE-5) inhibitors (e.g. sildenafil) may lead to symptomatic hypotension. Potentiates the BP lowering activity of other α-blockers and other antihypertensives.

Adverse Effects

Side effects of Doxazosin : >10% Dizziness (5-19%), Fatigue (8-12%), Headache (6-10%) 1-10% Vertigo (7%), Upper respiratory tract infection (URTI) (5%), Edema (3-4%), Rhinitis (3%), Dyspnea (1-3%), Abdominal pain (2%), Hypotension (1-2%), Nausea (1-2%), Orthostatic hypotension (dose related) (0.3-2%), Anxiety (1%), Palpitations (1%)

Mechanism of Action

Hypertension: Blocks postsynaptic alpha1 receptors; alpha blockade causes arterial, arteriolar, and venous dilation; decreases total peripheral resistance and blood pressure Benign prostatic hyperplasia (BPH): Blocks alpha1 receptors in prostatic stromal and bladder tissues; reduces sympathetic tone-induced urethral stricture responsible for BPH symptoms