Metolazone Side Effects

Some side effects of metolazone may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to metolazone: oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking metolazone: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using this medication and call your doctor at once if you have a serious side effect such as:

• dry mouth, thirst, nausea, vomiting;

• feeling weak, drowsy, restless, or light-headed;

• fast or uneven heartbeat;

• muscle pain or weakness;

• chest pain;

• urinating less than usual or not at all; or

• numbness or tingly feeling.

Less serious side effects of metolazone may include:

• dizziness;

• headache;

• joint pain;

• a red, blistering, peeling skin rash; or

• blurred vision.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to metolazone: oral tablet

Metabolic

A rare case of hyperosmolar nonketotic hyperglycemia is associated with metolazone.

Metabolic side effects are the most common and profound. The rapid onset of hyponatremia or hypokalemia is often sudden and may be profound, particularly if metolazone is given with a loop diuretic. Hypokalemia may be important in patients with underlying cardiac arrhythmias. Metolazone may increase serum calcium and uric acid levels and lower serum magnesium and phosphate levels. Glucose intolerance is reported in rare cases.

Cardiovascular

Cardiovascular side effects are uncommon. Postural hypotension is reported in less than 5% of patients. Rare cases of venous thrombosis are reported, thought to be due to metolazone-induced hypovolemia and increased serum concentrations of clotting factors. Rare cardiovascular side effects also include palpitations, hypovolemia, and chest pain.

Renal

Renal insufficiency, manifest as a rise in serum creatinine and BUN, may occur, although, in most cases, creatinine clearance increases as a result of metolazone therapy.

Nervous system

Nervous system side effects include headache, dizziness, and fatigue. Two cases of syncope and seizures are reported. Metolazone-induced hypovolemia and electrolyte changes may induce hepatic encephalopathy in some patients.

It is not clear whether the patients who developed syncope and seizure activity were hypotensive or hypovolemic at the time of the seizures or that metolazone can definitively be implicated. In one case the patient was also taking theophylline and had hypomagnesemia, which may be a complication of metolazone therapy.

Hypersensitivity

Hypersensitivity reactions include rare case reports of necrotizing vasculitis, angiitis, and pruritic rashes.

A case of cutaneous hypersensitivity angiitis has been reported in a patient who had previously tolerated thiazide diuretics, indicating that, despite the chemical similarity between thiazides and metolazone, there is not necessarily cross-reactivity.

Hematologic

Hematologic abnormalities are rare. Cases of reversible hypoplastic anemia, aplastic anemia, agranulocytosis, and mild leukopenia are reported.

Gastrointestinal

Gastrointestinal side effects are rare, and include a case of acute pancreatitis. Nausea, vomiting, anorexia, and abdominal bloating are also rare.

Hepatic

Hepatic side effects include a rare case of cholestatic jaundice.

Musculoskeletal

Musculoskeletal cramps are associated with metolazone therapy, as with other diuretics, and may be associated with electrolyte disorders and rapid intravascular volume shifts.

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