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.
Hypokalemia may develop, especially with brisk diuresis,
when severe cirrhosis is present, during concomitant use of corticosteroids or
ACTH, or after prolonged therapy.
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
Latent diabetes mellitus may become manifest during thiazide
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
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
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
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
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