Acute Toxicity

Several cases of overdosage with Lopressor have been reported, some leading to death. No deaths have been reported with hydrochlorothiazide.

Oral LD ₅₀'s (mg/kg): mice, 1158 (Lopressor); rats, 3090 (Lopressor), 2750 (hydrochlorothiazide).

Signs and Symptoms

Lopressor: Potential signs and symptoms associated with overdosage with Lopressor are bradycardia, hypotension, bronchospasm, and cardiac failure.

Hydrochlorothiazide: The most prominent feature of poisoning is acute loss of fluid and electrolytes.

Cardiovascular: Tachycardia, hypotension, shock.

Neuromuscular: Weakness, confusion, dizziness, cramps of the calf muscles, paresthesia, fatigue, impairment of consciousness.

Digestive: Nausea, vomiting, thirst.

Renal: Polyuria, oliguria, or anuria (due to hemoconcentration).

Laboratory Findings: Hypokalemia, hyponatremia, hypochloremia, alkalosis; increased BUN (especially in patients with renal insufficiency).

Combined Poisoning: Signs and symptoms may be aggravated or modified by concomitant intake of antihypertensive medication, barbiturates, curare, digitalis (hypokalemia), corticosteroids, narcotics, or alcohol.

Treatment

There is no specific antidote.

On the basis of the pharmacologic actions of Lopressor and hydrochlorothiazide, the following general measures should be employed:

Elimination of the Drug: Inducement of vomiting, gastric lavage, and activated charcoal.

Bradycardia: Atropine should be administered. If there is no response to vagal blockade, isoproterenol should be administered cautiously.

Hypotension: The patient's legs should be elevated and lost fluid and electrolytes (potassium, sodium) should be replaced. A vasopressor should be administered, e.g., levarterenol or dopamine.

Bronchospasm: A beta₂-stimulating agent and/or a theophylline derivative should be administered.

Cardiac Failure: A digitalis glycoside and diuretic should be administered. In shock resulting from inadequate cardiac contractility, administration of dobutamine, isoproterenol, or glucagon may be considered.

Surveillance: Fluid and electrolyte balance (especially serum potassium) and renal function should be monitored until conditions become normal.

Lopressor

Lopressor is contraindicated in sinus bradycardia, heart block greater than first degree, cardiogenic shock, and overt cardiac failure (see WARNINGS).

Hypersensitivity to Lopressor and related derivatives, or to any of the excipients; hypersensitivity to other beta blockers (cross sensitivity between beta blockers can occur).

Sick-sinus syndrome.

Severe peripheral arterial circulatory disorders.

Hydrochlorothiazide

Hydrochlorothiazide is contraindicated in patients with anuria or hypersensitivity to this or other sulfonamide-derived drugs (see WARNINGS).

Last reviewed on RxList: 5/9/2011
This monograph has been modified to include the generic and brand name in many instances.