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Lopressor HCT (Hydrochlorothiazide / Metoprolol Tartrate) - Drug Interactions, Contraindications, Overdosage, etc

 
 



DRUG INTERACTIONS

Drug/Drug Interactions

Lopressor: Catecholamine-depleting drugs (e.g., reserpine) may have an additive effect when given with beta-blocking agents. Patients treated with Lopressor plus a catecholamine depletor should therefore be closely observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension.

Both digitalis glycosides and beta blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia.

Risk of Anaphylactic Reaction:   While taking beta blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic, or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.

OVERDOSAGE

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.

CONTRAINDICATIONS

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.

Pheochromocytoma (see WARNINGS).

Hydrochlorothiazide

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

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