Doxazosin

Brand names: Cardura, Doxazosin Mesylate, Doxazosin mesylate, Doxazosin, DOXAZOSIN

Warnings

No boxed warning. Contraindicated in patients with "hypersensitivity to doxazosin, other quinazolines, or any other ingredient." Key warnings: "postural hypotension with or without syncope may occur," especially with the first dose; risk of "Intraoperative Floppy Iris Syndrome" during cataract surgery in patients on or previously treated with alpha1-blockers; BPH patients should be screened for prostate cancer before starting therapy; alpha1 antagonists "have been associated with priapism (painful penile erection)."

Contraindications

4 CONTRAINDICATIONS The use of doxazosin tablets is contraindicated in patients with a hypersensitivity to doxazosin, other quinazolines (e.g., prazosin, terazosin), or any of its components. Hypersensitivity to doxazosin, other quinazolines, or any other ingredient in doxazosin tablets. ( 4 )

Overdose

10 OVERDOSAGE Experience with doxazosin overdosage is limited. Two adolescents, who each intentionally ingested 40 mg doxazosin with diclofenac or acetaminophen, were treated with gastric lavage with activated charcoal and made full recoveries. A two-year-old child who accidently ingested 4 mg doxazosin was treated with gastric lavage and remained normotensive during the five-hour emergency room observation period. A six-month-old child accidentally received a crushed 1 mg tablet of doxazosin and was reported to have been drowsy. A 32-year-old female with chronic renal failure, epilepsy, and depression intentionally ingested 60 mg doxazosin (blood level = 0.9 mcg/mL; normal values in hypertensives = 0.02 mcg/mL); death was attributed to a grand mal seizure resulting from hypotension. A 39-year-old female who ingested 70 mg doxazosin, alcohol, and Dalmane ® (flurazepam) developed hypotension which responded to fluid therapy. The oral LD 50 of doxazosin is greater than 1000 mg/kg in mice and rats. The most likely manifestation of overdosage would be hypotension, for which the usual treatment would be intravenous infusion of fluid. As doxazosin is highly protein bound, dialysis would not be indicated.

Drug interactions

7 DRUG INTERACTIONS Strong cytochrome P450 (CYP) 3A inhibitors may increase exposure to doxazosin and increased risk of hypotension ( 7.1 ) Concomitant administration of doxazosin with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension. ( 7.2 ) 7.1 CYP 3A Inhibitors In vitro studies suggest that doxazosin is a substrate of CYP 3A4. Strong CYP3A inhibitors may increase exposure to doxazosin. Monitor blood pressure and for symptoms of hypotension when doxazosin is used concomitantly with strong CYP3A inhibitors [see Clinical Pharmacology (12.3) ] . 7.2 Phosphodiesterase-5 (PDE-5) Inhibitors Concomitant administration of doxazosin with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension. Monitor blood pressure and for symptoms of hypotension [see Warnings and Precautions (5.1) ] .

Uses

Doxazosin mesylate tablets are indicated for: - Treatment of the "signs and symptoms of Benign Prostatic Hyperplasia (BPH)" - "Treatment of Hypertension," to lower blood pressure and reduce the risk of cardiovascular events.

Dosage forms & strengths

Tablet Tablet, Multilayer, Extended Release TABLET

DOXAZOSIN 1 mg DOXAZOSIN 2 mg DOXAZOSIN 4 mg DOXAZOSIN 8 mg DOXAZOSIN MESYLATE 1 mg DOXAZOSIN MESYLATE 2 mg DOXAZOSIN MESYLATE 4 mg DOXAZOSIN MESYLATE 8 mg Doxazosin Mesylate 1 mg Doxazosin Mesylate 2 mg Doxazosin Mesylate 4 mg Doxazosin Mesylate 8 mg DOXAZOSIN MESYLATE 8 mg/1 DOXAZOSIN MESYLATE 4 mg/1 DOXAZOSIN MESYLATE 2 mg/1 DOXAZOSIN MESYLATE 1 mg/1

2 DOSAGE AND ADMINISTRATION For the treatment of BPH: Initiate therapy at 1 mg once daily. Dose may be titrated at 1 to 2-week intervals, up to 8 mg once daily. ( 2.2 ) For the treatment hypertension: Initiate therapy at 1 mg once daily. Dose may be titrated as needed, up to 16 mg once daily. ( 2.3 ) 2.1 Dosing Information Following the initial dose and with each dose increase of doxazosin tablets, monitor blood pressure for at least 6 hours following administration. If doxazosin tablets administration is discontinued for several days, therapy should be restarted using the initial dosing regimen. 2.2 Benign Prostatic Hyperplasia The recommended initial dosage of doxazosin tablets is 1 mg given once daily either in the morning or evening. Depending on the individual patient’s urodynamics and BPH symptomatology, the dose may be titrated at 1 to 2 week intervals to 2 mg, and thereafter to 4 mg and 8 mg once daily. The maximum recommended dose for BPH is 8 mg once daily. Routinely monitor blood pressure in these patients. 2.3 Hypertension The initial dosage of doxazosin tablets is 1 mg given once daily. Daily dosage may be doubled up 16 mg once daily, as needed, to achieve the desired reduction in blood pressure.