Pregnancy Risk Category C
How supplied
Tablets: 100 mg, 200 mg, 300 mg
Injection: 5 mg/ml
Action
Unknown. Possibly related to reduced peripheral vascular resistance mainly as a result of alpha and beta blockade.
Indications & dosage
Hypertension--
Adults: 100 mg P.O. b.i.d. with or without a diuretic. If needed, dosage is increased to 200 mg b.i.d. after 2 days. Further increases may be made q 2 to 3 days until optimum response is reached. Usual maintenance dose is 200 to 400 mg b.i.d.
Severe hypertension, hypertensive emergencies--
Adults: 200 mg diluted in 160 ml of D5W, infused at 2 mg/minute until satisfactory response is obtained; then infusion is stopped. May be repeated q 6 to 12 hours.
Or, administered by repeated I.V. injection: initially, 20 mg I.V. slowly over 2 minutes. Repeat injections of 40 to 80 mg q 10 minutes until maximum dose of 300 mg is reached, p.r.n.
Adverse reactions
CNS: vivid dreams, fatigue, headache, paresthesia, syncope, transient scalp tingling, dizziness.
CV: orthostatic hypotension, ventricular arrhythmias.
EENT: nasal stuffiness.
GI: nausea, vomiting.
GU: sexual dysfunction, urine retention.
Respiratory: dyspnea, bronchospasm.
Skin: rash.
Interactions
Drug-drug. Beta-adrenergic agonists: may blunt bronchodilator effect of these drugs in patients with bronchospasm. Therefore, greater than normal doses of these drugs may be needed.
Cimetidine: may enhance labetalol's effect. Give together cautiously.
Halothane: additive hypotensive effect. Monitor blood pressure closely.
Insulin, oral antidiabetics: can alter dosage requirements in previously stabilized diabetic patient. Observe patient carefully.
Effects on diagnostic tests
Drug may cause a false-positive increase of urine free and total catecholamine levels when measured by a nonspecific trihydroxindole fluorometric method. Drug causes increases in serum transaminases and blood urea levels.
Contraindications
Contraindicated in patients with hypersensitivity to drug; also contraindicated in those with bronchial asthma, overt cardiac failure, greater than first-degree heart block, cardiogenic shock, severe bradycardia, or other conditions associated with severe and prolonged hypotension.
Nursing considerations
I.V. administration
Patient teaching
*Liquid contains alcohol. **May contain tartrazine. †Canada ‡Australia §U.K. OTCOver the counter
Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING