Brands, Medical Use, Clinical Data
Drug Category
- Antihypertensive Agents
- Diuretics, Sulfamyl
Dosage Forms
- Tablet for oral administration (0.5mg)
Brands / Synonyms
Diulo; Metalazone; Metalozone; Metenix; Metolazona [INN-Spanish]; Metolazone; Metolazonum [INN-Latin]; Microx; Mykrox; Oldren; Xuret; Zaroxolyn; Zaroxolyn
Indications
For the treatment of hypertension, alone or in combination with other antihypertensive drugs of a different class.
Pharmacology
Metolazone is a quinazoline diuretic, with properties generally similar to the thiazide diuretics. A proximal action of metolazone has been shown in humans by increased excretion of phosphate and magnesium ions and by a markedly increased fractional excretion of sodium in patients with severely compromised glomerular filtration. This action has been demonstrated in animals by micropuncture studies.
Mechanism of Action
The actions of metolazone result from interference with the renal tubular mechanism of electrolyte reabsorption. Metolazone acts primarily to inhibit sodium reabsorption at the cortical diluting site and to a lesser extent in the proximal convoluted tubule. Sodium and chloride ions are excreted in approximately equivalent amounts. The increased delivery of sodium to the distal tubular exchange site results in increased potassium excretion. Metolazone does not inhibit carbonic anhydrase. The antihypertensive mechanism of action of metolazone is not fully understood but is presumed to be related to its saluretic and diuretic properties.
Absorption
Peak blood levels are obtained within 2 to 4 hours of oral administration.
Toxicity
Symptoms of overdose include difficulty breathing, dizziness, dizziness on standing up, drowsiness, fainting, irritation of the stomach and intestines, and lethargy leading to coma.
Biotrnasformation / Drug Metabolism
Not Available
Contraindications
Anuria, hepatic coma or precoma, known allergy or hypersensitivity to metolazone.
Drug Interactions
Diuretics: Furosemide and probably other loop diuretics given concomitantly with metolazone can cause unusually large or prolonged losses of fluid and electrolytes.
Other Antihypertensives: When MYKROX Tablets 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.
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 MYKROX Tablets three days before elective surgery.
Salicylates and Other Non-Steroidal Anti-Inflammatory Drugs: May decrease the antihypertensive effects of MYKROX Tablets.
Sympathomimetics: Metolazone may decrease arterial responsiveness to norepinephrine, but this diminution is not sufficient to preclude effectiveness of the pressor agent for therapeutic use.
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.
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