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labetalol hydrochloride
Normodyne, Presolol‡, Trandate

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

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