Labetalol Hydrochloride

Indications

Labetalol Hydrochloride is used for: Hypertension, Hypotensive anaesthesia

Adult Dose

Oral Hypertension Adult: Initially, 100 mg bid, may increase gradually according to patients response to 200-400 mg bid. Max: 2.4 g/day in 2-4 divided doses. Elderly: Initially, 50-100 mg bid. Maintenance: 100-200 mg bid. Intravenous Emergency treatment of hypertension Adult: 20 mg injected slowly for at least 2 min, followed by 40-80 mg dose every 10 min, if necessary up to 300 mg. Patient should remain supine during and 3 hr after the procedure. Hypertension in pregnancy Adult: Start infusion at a rate of 20 mg/hr, doubled every 30 min until a satisfactory response is achieved or a dose of 160 mg/hr is reached. Hypertension after myocardial infarction Adult: Initiate infusion at a rate of 15 mg/hr, then increase gradually until a favourable response is obtained or a dose of 120 mg/hr is reached. Hypotensive anaesthesia Adult: Initially, 10-20 mg, increase at 5-10 mg increments if satisfactory hypotension is not achieved after 5 min. Administer higher initial doses if halothane anaesth is not used. Incompatibility: Na bicarbonate 5% and alkaline solutions.

Child Dose

Hypertensive Emergency 0.4-1 mg/kg/hr by continuous IV infusion; not to exceed 3 mg/kg/hr

Renal Dose

Administration

Should be taken with food. Take immediately after meals. IV Preparation Standard diluent: 500 mg/250 mL D5W Minimum volume: 250 mL D5W IV Administration Requires infusion pump Slow direct IV push administered over 2 minutes Loading infusions (2 mg/min) require close monitoring of HR and BP and are terminated after response occurs or a cumulative dose of 300 mg is reached Continuous infusions of 2-6 mg/hr have been used in some settings and should not be confused with loading infusions

Contra Indications

2nd and 3rd degree heart block, cardiogenic shock, obstructive airway disease e.g. bronchial asthma, uncompensated heart failure, severe bradycardia, sick sinus syndrome, Prinzmetal's angina, severe peripheral arterial disease.

Precautions

Phaeochromocytoma, compensated heart failure, nonallergic bronchospasm. Avoid abrupt withdrawal. DM. Hepatic impairment. Perform LFTs. Elderly. Pregnancy and lactation. Lactation: Small amounts excreted; use with caution

Pregnancy-Lactation

Pregnancy category: C Lactation: Small amounts excreted; use with caution

Interactions

Synergistic hypotensive effect w/ halothane. Increased absolute bioavailability w/ cimetidine. Decreased absolute bioavailability w/ glutethimide. Additive hypotensive effect w/ nitroglycerin. Increased incidence of tremor w/ TCAs. Increased risk of bradycardia and heart block w/ Ca channel blocker (e.g. verapamil, diltiazem).

Side Effects

Side effects of Labetalol Hydrochloride : >10% Dizziness (1-20%), Lightheadedness (1-20%), Nausea (<19%), Tingling sensation of scalp (4-12%), Fatigue (1-11%) 1-10% Elevated serum blood urea nitrogen (BUN) (<8%), Elevated serum creatinine (8%), Congestion of nasal sinus (1-6%), Orthostatic hypotension (1-5%), Absence of ejaculation (<5%), Paresthesia (<5%), Elevated liver enzymes (4%), Diaphoresis (<4%), Edema (<2%), Bronchospasm (1-2%), Dyspnea (1-2%), Pruritus (1%), Rash (1%), Altered taste sense (1%), Ventricular arrhythmia (1%; IV) Frequency Not Defined Angioedema, Bradycardia, Alopecia, Cholestatic jaundice, Depression, Diabetes insipidus, Hepatitis, Raynaud syndrome, Toxic myopathy, Urinary retention, Urticaria, Raynaud phenomenon Potentially Fatal: Hepatic injury.

Mode of Action

Labetalol competitively inhibits the adrenergic stimulation of beta-receptors w/in the myocardium, bronchial and vascular smooth muscle, and alpha1-receptors w/in vascular smooth muscle. It also has some intrinsic beta2-agonist and membrane-stabilising activity.