Details About Overdose or Poisoning Generic Salt :: Labetalol
Drug Pharmacology ::
I. Pharmacology. Labetalolis a mixed alpha- and beta-adrenergic antagonist; after intravenousadministration, the nonselective beta-antagonist properties areapproximately sevenfold greater than the alpha-1 antagonist activity.Hemodynamic effects generally include decreases in heart rate, bloodpressure, and systemic vascular resistance. Atrioventricular conductionvelocity may be decreased. After intravenous injection, hypotensiveeffects are maximal within 10–15 minutes and persist for about 2–4hours. The drug is eliminated by hepatic metabolism and has a half-lifeof 5–6 hours.
Drug Indications ::
Indications. Labetalolmay be used to treat hypertension accompanied by tachycardia associatedwith stimulant drug overdose (eg, cocaine or amphetamines). Note:Hypertension with bradycardia suggests excessive alpha-mediatedvasoconstriction (see Hypertension, Pseudoephedrine, Phenylephrine, andOther Decongestants); in this case, a pure alpha blocker such asphentolamine (Phentolamine) is preferable, because the reversal ofbeta-2–mediated vasodilation may worsen hypertension. In addition, itmay have an unpredictable effect on coronary vascular tone; otheragents, such as nitroglycerin, may be preferable for stimulant-inducedcoronary vasoconstriction.
Drug Contra-Indications ::
Congestive heart failure.
Drug Adverse Effects ::
IV. Adverse effects
Paradoxichypertension may result when labetalol is used in the presence ofstimulant intoxicants that have strong mixed alpha- and beta-adrenergicagonist properties (eg, cocaine, amphetamines) owing to the relativelyweak alpha-antagonist properties of labetalol compared with itsbeta-blocking ability. (This has been reported with propranolol but notwith labetalol.)
Orthostatic hypotension and negative inotropic effects may occur.
Dyspnea and bronchospasm may result, particularly in asthmatics.
Nausea, abdominal pain, diarrhea, tremors, dizziness, and lethargy have been reported.
E. Use in pregnancy. FDAcategory C (indeterminate). This does not preclude its acute,short-term use for a seriously symptomatic patient (see Table III–1).
Drug Lab Interactions ::
Drug or laboratory interactions
Additive blood pressure lowering with other antihypertensive agents, halothane, or nitroglycerin.
Cimetidine increases the oral bioavailability of labetalol.
Labetalol is incompatible with 5% sodium bicarbonate injection (forms a precipitate).
Labetalolmay cause false-positive elevation of urinary catecholamine levels andcan produce a false-positive test for amphetamines on urine drugscreening.
Drug Dose Management ::
Dosage and method of administration
Adult. Give20-mg slow (over 2 minutes) IV bolus initially; repeat with 40- to80-mg doses at 10-minute intervals until blood pressure is controlledor a cumulative dose of 300 mg is achieved (most patients will respondto total doses of 50–200 mg). Alternatively, administer a constantinfusion of 0.5–2 mg/min (adjust rate) until blood pressure iscontrolled or a 300-mg cumulative dose is reached. After this, giveoral labetalol starting at 100 mg twice daily.
Children older than 12 years. Initial dose of 0.25 mg/kg is given intravenously over 2 minutes.
Drug Chemical Formulations ::
Parenteral. Labetalolhydrochloride (Normodyne, Trandate), 5 mg/mL, 20- and 40-mL multidosevials (with EDTA and parabens as preservative), and 4- and 8-mLprefilled syringes.
Oral. Labetalol hydrochloride (Normodyne, Trandate, others), 100-, 200-, and 300-mg tablets.
The suggested minimum stocking level to treat a 70-kg adult for the first 24 hours is two vials (5 mg/mL, 40 mL each).