Overview
11 DESCRIPTION Doxazosin mesylate is a quinazoline compound that is a selective inhibitor of the alpha 1 subtype of alpha-adrenergic receptors. The chemical name of doxazosin mesylate is 1-(4-amino-6,7- dimethoxy-2-quinazolinyl)-4-(1,4-benzodioxan-2-ylcarbonyl) piperazine methanesulfonate.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Benign Prostatic Hyperplasia (BPH) The symptoms associated with benign prostatic hyperplasia (BPH), such as urinary frequency, nocturia, weak stream, hesitancy, and incomplete emptying are related to two components, anatomical (static) and functional (dynamic). The static component is related to an increase in prostate size caused, in part, by a proliferation of smooth muscle cells in the prostatic stroma. However, the severity of BPH symptoms and the degree of urethral obstruction do not correlate well with the size of the prostate. The dynamic component of BPH is associated with an increase in smooth muscle tone in the prostate and bladder neck.
Indications
- 1 INDICATIONS AND USAGE Doxazosin tablets are an alpha 1 adrenergic antagonist indicated for: • Signs and symptoms of Benign Prostatic Hyperplasia (BPH) • Treatment of HypertensionTreatment of Hypertension 1.1 Benign Prostatic Hyperplasia (BPH) Doxazosin tablets are indicated for the treatment of the signs and symptoms of BPH. 1.2 Hypertension Doxazosin tablets are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions.
Common Doses
- 1 mg
- 8 mg
- 16 mg
- 2 mg
Dosage
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.
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 )
Side Effects
- 6 ADVERSE REACTIONS The most commonly reported adverse reactions from clinical trials are Fatigue, malaise, hypotension, and dizziness. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Apotex Corp at 1-800-706-5575 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
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 tablets 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.