METOLAZONE Drug Interactions: What You Need to Know

Drug Interactions Diuretics Furosemide and probably other loop diuretics given concomitantly with metolazone can cause unusually large or prolonged losses of fluid and electrolytes (see WARNINGS ).

Other Antihypertensives

When metolazone tablets, USP, are used with other antihypertensive drugs, care must be taken, especially during initial therapy. Dosage adjustments of other antihypertensives may be necessary. Alcohol, Barbiturates, And Narcotics The hypotensive effects of these drugs may be potentiated by the volume contraction that may be associated with metolazone therapy.

Digitalis Glycosides

Diuretic-induced hypokalemia can increase the sensitivity of the myocardium to digitalis. Serious arrhythmias can result. Corticosteroids Or ACTH May increase the risk of hypokalemia and increase salt and water retention.

Lithium

Serum lithium levels may increase (see WARNINGS ).

Curariform Drugs

Diuretic-induced hypokalemia may enhance neuromuscular blocking effects of curariform drugs (such as tubocurarine) – the most serious effect would be respiratory depression which could proceed to apnea. Accordingly, it may be advisable to discontinue metolazone tablets, USP, three days before elective surgery.

Salicylates And Other

Non-Steroidal Anti-Inflammatory Drugs May decrease the antihypertensive effects of metolazone tablets, USP.

Sympathomimetics

Metolazone may decrease arterial responsiveness to norepinephrine, but this diminution is not sufficient to preclude effectiveness of the pressor agent for therapeutic use.

Insulin And Oral Antidiabetic Agents

See Glucose Tolerance under PRECAUTIONS , General .

Methenamine

Efficacy may be decreased due to urinary alkalizing effect of metolazone.

Anticoagulants

Metolazone, as well as other thiazide-like diuretics, may affect the hypoprothrombinemic response to anticoagulants; dosage adjustments may be necessary.

CONTRAINDICATIONS Anuria, hepatic coma or precoma, known allergy or hypersensitivity to metolazone.

WARNINGS Rapid Onset Hyponatremia And/Or Hypokalemia Rarely, the rapid onset of severe hyponatremia and/or hypokalemia has been reported following initial doses of thiazide and non-thiazide diuretics. When symptoms consistent with severe electrolyte imbalance appear rapidly, drug should be discontinued and supportive measures should be initiated immediately. Parenteral electrolytes may be required. Appropriateness of therapy with this class of drugs should be carefully reevaluated.

Hypokalemia

Hypokalemia may occur with consequent weakness, cramps, and cardiac dysrhythmias. Serum potassium should be determined at regular and appropriate intervals, and dose reduction, potassium supplementation or addition of a potassium-sparing diuretic instituted whenever indicated. Hypokalemia is a particular hazard in patients who are digitalized or who have or have had a ventricular arrhythmia; dangerous or fatal arrhythmias may be precipitated. Hypokalemia is dose related.

Concomitant Therapy

Lithium In general, diuretics should not be given concomitantly with lithium because they reduce its renal clearance and add a high risk of lithium toxicity. Read prescribing information for lithium preparations before use of such concomitant therapy.

Furosemide

Unusually large or prolonged losses of fluids and electrolytes may result when metolazone tablets, USP, are administered concomitantly to patients receiving furosemide (see PRECAUTIONS , Drug Interactions ).

Other Antihypertensive Drugs

When metolazone tablets, USP, are used with other antihypertensive drugs, particular care must be taken to avoid excessive reduction of blood pressure, especially during initial therapy. Cross –Allergy Cross-allergy may occur when metolazone tablets, USP, are given to patients known to be allergic to sulfonamide-derived drugs, thiazides, or quinethazone.

Sensitivity Reactions

Sensitivity reactions (e.g., angioedema, bronchospasm) may occur with or without a history of allergy or bronchial asthma and may occur with the first dose of metolazone tablets, USP.