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Cautions

Contraindications

• Anuria.
• Known hypersensitivity to hydrochlorothiazide, other thiazides, or any ingredient in the formulation.
• Although manufacturers state allergy to other sulfonamide derivatives is a contraindication, evidence to support cross-sensitivity is limited, and history of sensitivity to sulfonamide anti-infectives (“sulfa sensitivity”) should not be considered an absolute contraindication.

Warnings/Precautions

Warnings

Severe Renal Impairment

Use with caution; thiazides decrease GFR and may precipitate azotemia.

Effects may be cumulative in impaired renal function.

Hepatic Impairment

Use with caution in hepatic impairment or progressive liver disease (particularly with associated potassium deficiency); electrolyte imbalance may precipitate hepatic coma.

Discontinue immediately if signs of impending hepatic coma appear.

Hypotensive Agents

May potentiate effects of other hypotensive agents. Although additive or potentiated antihypertensive effects usually are used to therapeutic advantage, hypotension could occur. (See Interactions.)

Lupus Erythematosus

Possible exacerbation or activation of systemic lupus erythematosus.

Lithium

Generally, do not use with lithium salts. (See Interactions.)

Sensitivity Reactions

Hypersensitivity

May occur with or without history of allergy or bronchial asthma.

Sulfonamide cross-sensitivity unlikely. (See Contraindications under Cautions.)

General Precautions

Electrolyte Imbalance

Monitor for fluid or electrolyte imbalance (hyponatremia, hypochloremic alkalosis, hypokalemia).

Observe for signs of electrolyte imbalance (e.g., dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, confusion, seizures, oliguria, muscle pains, cramps, muscular fatigue, hypotension, tachycardia, nausea, vomiting).

Perform periodic serum electrolyte determinations (particularly of potassium, sodium, chloride, and bicarbonate); institute measures to maintain normal serum concentrations if necessary.

Serum and urinary electrolyte measurements are especially important with diabetes mellitus, vomiting, diarrhea, parenteral fluid therapy, or expectations of excessive diuresis.

Weekly (or more frequent) electrolyte measurement recommended early in treatment; possible to extend interval between measurements to ≥3 months when electrolyte response has stabilized.

Hypokalemia

May occur after brisk diuresis, when cirrhosis is present, or with prolonged therapy; inadequate oral electrolyte intake may contribute.

May cause cardiac arrhythmias, exaggerate cardiac response to cardiac glycoside toxicity (increase ventricular irritability).

Use potassium-sparing diuretics and/or potassium supplementation to avoid or treat hypokalemia.

Hypochloremia

Generally mild, usually does not require specific treatment except in renal or hepatic impairment.

Chloride replacement may be required for metabolic acidosis.

Hyponatremia

Dilutional hyponatremia may occur in edematous patients in hot weather; appropriate treatment usually is water restriction rather than salt administration except when hyponatremia is life-threatening.

In actual salt depletion, appropriate replacement is treatment of choice.

Gout

Hyperuricemia or precipitation of gout may occur.

Hyperglycemia

In diabetic patients, dosage adjustment of insulin or oral hypoglycemics may be required; hyperglycemia may occur and latent diabetes mellitus may become evident.

Sympathectomy

Antihypertensive effect may be enhanced after sympathectomy.

Hypomagnesemia

May increase magnesium urinary excretion, resulting in hypomagnesemia.

Hypercalcemia

May decrease calcium urinary excretion, cause slight intermittent serum calcium increase in absence of known calcium metabolism disorder; marked hypercalcemia may indicate hyperparathyroidism.

Discontinue prior to performing parathyroid tests.

Hyperlipidemia

May increase cholesterol and triglyceride concentrations.

Clinical importance of these changes is unknown. Diet low in saturated fat and cholesterol usually compensates.

Hypotensive Effects

Orthostatic hypotension rarely occurs.

Specific Populations

Pregnancy

Category B.

Although hypertension during pregnancy responds well to thiazides, and the drugs had been used widely in the past for preeclampsia and eclampsia, such use no longer is recommended and other antihypertensives (e.g., methyldopa, hydralazine, labetalol) currently are preferred. Diuretics are not recommended for pregnancy-induced hypertension because of the maternal hypovolemia associated with this form of hypertension; decreased placental perfusion is possible. Diuretics are considered second-line agents for control of chronic hypertension in pregnant women.

Thiazides should not be used as routine therapy in pregnant women with mild edema who are otherwise healthy.

Edema associated with pregnancy generally responds well to thiazides except when caused by renal disease.

Lactation

Distributed into milk. Discontinue nursing or the drug.

Although hydrochlorothiazide use generally is considered compatible with breast-feeding, thiazides can reduce milk volume and thus suppress lactation.

Pediatric Use

No controlled studies in children; use is supported by experience and published literature about hypertension treatment in children.

Geriatric Use

Elderly may be at increased risk of dilutional hyponatremia, especially underweight females with poor oral fluid and electrolyte intake or excessive low-sodium nutritional supplement intake. (See Hyponatremia under Warnings/Precautions.)

Increased incidence of adverse effects and excessive reduction in BP in those >65 years of age. (See Geriatric Patients under Dosage and Administration.)

Hepatic Impairment

Use caution. (See Hepatic Impairment under Warnings.)

Renal Impairment

Use caution. (See Severe Renal Impairment under Warnings.)

Consider interruption or discontinuance if progressive renal impairment (rising nonprotein nitrogen, BUN, or serum creatinine) occurs.

Common Adverse Effects

Potassium depletion, hyperuricemia (usually asymptomatic rarely leading to gout). Hypochloremic alkalosis in patients at risk (e.g., hypokalemic patients). Hyperglycemia and glycosuria in diabetics.