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Methyclothiazide (methyclothiazide (methyclothiazide (methyclothiazide tablet 5 mg) tablet 5 mg) tablet 5 mg) shares with other thiazides the propensity to deplete potassium reserves to an unpredictable degree.
There have been isolated reports that certain non-edematous individuals developed severe fluid and electrolyte derangements after only brief exposure to normal doses of thiazide and non-thiazide diuretics.
All patients should be observed for clinical signs of electrolyte imbalances such as dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, and gastrointestinal disturbances such as nausea and vomiting.
Interference with adequate oral electrolyte intake will also contribute to hypokalemia. Hypokalemia may be avoided or treated by use of potassium supplements or foods with a high potassium content.
Any chloride deficit is generally mild and usually does not require specific treatment except under extraordinary circumstances (as in liver disease or renal disease). Dilutional hyponatremia may occur in edematous patients in hot weather; appropriate therapy is water restriction rather than administration of salt, except in rare instances when the hyponatremia is life threatening. In actual salt depletion, appropriate replacement is the therapy of choice.
The antihypertensive effects of the drug may be enhanced in the postsympathectomy patient.
If progressive renal impairment becomes evident as indicated by a rising nonprotein nitrogen or blood urea nitrogen, a careful reappraisal of therapy is necessary with consideration given to withholding or discontinuing diuretic therapy.
Thiazides may decrease urinary calcium excretion. Thiazides may cause intermittent and slight elevation of serum calcium in the absence of known disorders of calcium metabolism. Marked hypercalcemia may be evidence of hidden hyperparathyroidism.
Thiazides should be discontinued before carrying out tests for parathyroid function.
Thiazides may cause increased concentrations of total serum cholesterol, total triglycerides, and low-density lipoproteins in some patients. Use thiazides with caution in patients with moderate or high cholesterol concentrations and in patients with elevated triglyceride levels.
Initial and periodic determinations of serum electrolytes should be performed at appropriate intervals for the purpose of detecting possible electrolyte imbalances such as hyponatremia, hypochloremic alkalosis, and hypokalemia. Serum and urine electrolyte determinations are particularly important when a patient is vomiting excessively or receiving parenteral fluids.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No data are available concerning the potential for carcinogenicity or mutagenicity in animals or humans. Methyclothiazide (methyclothiazide (methyclothiazide (methyclothiazide tablet 5 mg) tablet 5 mg) tablet 5 mg) did not impair fertility in rats receiving up to 4 mg/kg/day (at least 20 times the maximum recommended human dose of 10 mg, assuming patient weight equal to or greater than 50 kg).
Teratogenic Effects. Pregnancy Category B
Reproduction studies performed in rats and rabbits at doses up to 4 mg/kg/day have revealed no evidence of harm to the fetus due to methyclothiazide (methyclothiazide (methyclothiazide (methyclothiazide tablet 5 mg) tablet 5 mg) tablet 5 mg) . There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Thiazides cross the placental barrier and appear in cord blood. The use of thiazides in pregnant women requires that the anticipated benefit be weighed against possible hazards to the fetus. These hazards include fetal or neonatal jaundice, thrombocytopenia and possible other adverse reactions that have occurred in the adult.
Thiazides are excreted in breast milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug taking into account the importance of the drug to the mother.
Safety and effectiveness in children have not been established.
Last reviewed on RxList: 6/4/2009
This monograph has been modified to include the generic and brand name in many instances.
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