phenoxybenzamine

REMS

Management of symptoms of pheochromocytoma (particularly hypertension and sweating) caused by adrenergic (sympathomimetic) excess.
Treatment of hypertension associated with adrenergic excess, including that produced by tyramine-containing foods in patients receiving MAO inhibitor therapy.

Unlabeled Use:

Treatment of peripheral vascular disease.

Action ⬆ ⬇

Produces long-lasting blockade of alpha-adrenergic receptors in smooth muscle and exocrine glands.
Blocks epinephrine- and norepinephrine-induced vasoconstriction, resulting in hypotension and tachycardia.

Therapeutic effects:

Reduction of symptoms of pheochromocytoma.

Pharmacokinetics ⬆ ⬇

Absorption: Variably absorbed from the GI tract.

Distribution: Unknown.

Metabolism/Excretion: Mostly metabolized by the liver.

Half-Life: 24 hr.

Time/Action Profile ⬆ ⬇

(alpha-adrenergic blockade)

ROUTE	ONSET	PEAK	DURATION
PO	1–4 hr	1 wk	3–4 days

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Shock (if fluid deficits have not been corrected).

Use Cautiously in:

Coronary or cerebral arteriosclerosis;
Renal impairment;
Peptic ulcer disease;
Respiratory infection;
OB: Although safety not established, has been used safely in the 3rd trimester of pregnancy;
Geri: More susceptible to hypotensive effects; dosage recommended;
Lactation: Lactation or children.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypotension, angina, HF, tachycardia

EENT: miosis, nasal congestion

GI: diarrhea, dry mouth, nausea, vomiting

GU: inhibition of ejaculation

Neuro: confusion, dizziness, drowsiness, headache, malaise, sedation, tiredness, weakness

Interactions ⬆ ⬇

Drug-drug:

Antagonizes the effects of alpha-adrenergic stimulants.
May ↓ the pressor response to ephedrine, or phenylephrine.
Hypotension, vasodilation, and tachycardia may be exaggerated by drugs that stimulate both alpha and beta receptors, such as epinephrine.
↓peripheral vasoconstriction from high doses of dopamine.
Additive CNS depression may occur with concurrent use of antihistamines,antidepressants,alcohol, opioids, or sedative/hypnotics.

Route/Dosage ⬆ ⬇

Dosage requires individual titration

PO (Adults ): 10 mg twice daily; ↑ by 10 mg/day at 2-day intervals. Usual maintenance dose is 20–40 mg 2–3 times daily.
PO (Children ): 0.2 mg/kg or 6 mg/m² daily (not to exceed 10 mg); dosage increments may be made at 4-day intervals. Usual maintenance dose is 0.4–1.2 mg/kg/day (12–36 mg/m²/day) in 3–4 divided doses.

Availability ⬆ ⬇

(Generic available)

Capsules: 10 mg

Assessment ⬆ ⬇

Monitor BP (sitting and lying), pulse, respiratory status, and diaphoretic episodes frequently, especially during initiation of therapy.

Lab Test Considerations:

Urinary catecholamine measurements should be made periodically to determine maximal dose.

Implementation ⬆ ⬇

Concurrent use of a beta-adrenergic blocker may be necessary to control reflex tachycardia.
PO: May be administered with meals or milk if GI irritation becomes a problem. Dosage reduction may be required.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication exactly as directed at the same time each day. Do not skip or double up on missed doses. Consult health care professional before discontinuation.
Medication may cause drowsiness or dizziness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
Caution patient to make position changes slowly to minimize orthostatic hypotension. Standing for long periods or exercising during hot weather may also induce orthostatic hypotension.
Inform patient that good oral hygiene, frequent mouth rinses, and sugarless gum or candy may reduce dryness of mouth. Health care professional should be notified if dryness persists >2 wk. Regular dental care is recommended; dry mouth may increase risk of caries and periodontal disease.
Advise patient to avoid use of alcohol or OTC cold preparations without consulting health care professional.
Inform patient that medication may cause nasal congestion, inhibition of ejaculation, and constriction of pupils, which may interfere with night vision. These effects usually decrease with continued therapy. Notify health care professional if these side effects persist.
Advise patient to inform health care professional of medication regimen before treatment or surgery.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇