doxazosin

Contraindicated in:

Hypersensitivity.

Use Cautiously in:

Hepatic impairment;
GI narrowing (XL only);
Patients undergoing cataract surgery (↑ risk of intraoperative floppy iris syndrome);
OB: Not a preferred antihypertensive during pregnancy ;
Pedi: Safety and effectiveness not established in children;
Geri: Appears on Beers list. ↑ risk of orthostatic hypotension in older adults. Avoid use for treatment of hypertension in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: first-dose orthostatic hypotension, arrhythmias, chest pain, edema, palpitations

Derm: flushing, rash, urticaria

EENT: blurred vision, conjunctivitis, epistaxis, intraoperative floppy iris syndrome

GI: abdominal discomfort, constipation, diarrhea, dry mouth, flatulence, nausea, vomiting

GU: ↓libido, priapism, sexual dysfunction

MS: arthralgia, myalgia

Neuro: dizziness, headache, depression, drowsiness, fatigue, nervousness, weakness.

Resp: dyspnea

Interactions ⬆ ⬇

Drug-drug:

↑risk of hypotension with sildenafil, tadalafil, vardenafil, other antihypertensives, nitrates, or acute ingestion of alcohol.
NSAIDs, sympathomimetics, or estrogens may ↓ effects of antihypertensive therapy.

Availability ⬆ ⬇

(Generic available)

Tablets: 1 mg; 2 mg; 4 mg; 8 mg
Extended-release tablets: 4 mg; 8 mg

Route/Dosage ⬆ ⬇

Hypertension

PO (Adults ): 1 mg once daily; may be gradually ↑ at 2-wk intervals to 2–16 mg/day; incidence of postural hypotension greatly ↑ at doses >4 mg/day.

Benign Prostatic Hyperplasia

PO (Adults ): Immediate release: 1 mg once daily; may be ↑ every 1–2 wk up to 8 mg/day; Extended release: 4 mg once daily (with breakfast); may be ↑ in 3–4 wk to 8 mg/day.

US Brand Names ⬆ ⬇

Action ⬆ ⬇

Dilates both arteries and veins by blocking postsynaptic alpha₁-adrenergic receptors.

Therapeutic effects:

Lowering of BP.
Increased urine flow and decreased symptoms of BPH.

Classifications ⬆ ⬇

Therapeutic Classification: antihypertensives

Pharmacologic Classification: peripherally acting antiadrenergics

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Unknown.

Protein Binding: 98–99%.

Metabolism/Excretion: Extensively metabolized by the liver.

Half-Life: 22 hr.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO‡	1–2 hr	2–6 hr	24 hr
PO-XL‡	5 wk	unknown	unknown

‡Antihypertensive effect.

‡Improved urinary flow and BPH symptoms.

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication. Advise patient to read Patient Information before starting therapy. Emphasize the importance of continuing to take this medication, even if feeling well. Instruct to take at the same time each day. Take missed doses as soon as remembered unless almost time for next dose. Do not double doses.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to avoid concurrent use of alcohol or OTC medications and herbal products without consulting health care professional, especially cough, cold, or allergy remedies.
May cause drowsiness or dizziness. Advise patient to avoid driving or other activities requiring alertness until response to medication is known.
Caution patient to change positions slowly to ↓ orthostatic hypotension. May cause syncopal episodes, especially within 1st 24 hr of therapy, with dose ↑, and with resumption of therapy after interruption.
Advise patient to notify other physicians of drug therapy.
Advise male patient to notify health care professional if priapism or erection lasts >4 hr; may lead to permanent impotence if not treated.
Emphasize the importance of follow-up visits to determine effectiveness of therapy.
Hypertension: Instruct patient and caregiver on proper technique for BP monitoring. Advise them to check BP weekly and report significant changes.
- Encourage patient to comply with additional interventions for hypertension (weight reduction, low-sodium diet, smoking cessation, moderation of alcohol consumption, regular exercise, stress management).
- Advise women of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

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Indications ⬇

Contraind./Precautions ⬆ ⬇