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Benzthiazide Side Effects

Applies to benzthiazide: oral tablet.


Metabolic changes associated with benzthiazide, as with other thiazide diuretics, are relatively common, especially when dosages greater than 100 mg are used. Mild hypokalemia (decrease of 0.5 mEq/L) occurs in up to 50% of treated patients, and may predispose patients to cardiac arrhythmias. Metabolic alkalosis, hyponatremia, hypomagnesemia, hypophosphatemia, hypercalcemia, hyperglycemia, hypercholesterolemia, and hyperuricemia are also relatively common. The electrolyte and intravascular fluid shifts that may occur during benzthiazide diuresis can provoke hepatic encephalopathy in patients with hepatic cirrhosis.[Ref]

Hyperuricemia may be an important consideration in patients with a history of gout. Hypophosphatemia and low serum magnesium concentrations may occur, but are usually clinically insignificant except in malnourished patients.[Ref]


Cardiovascular complications of diuretic therapy include orthostatic hypotension secondary to intravascular volume depletion, which can be aggravated by concomitant administration of alcohol, barbiturates or narcotics. Rare cases of cerebrovascular accident associated with thiazide-induced diuresis have been reported.[Ref]


Hypersensitivity reactions usually involve the skin (cutaneous vasculitis, urticaria, rash, purpura), but may also involve the gastrointestinal system (nausea, vomiting, or diarrhea), the genitourinary system (interstitial nephritis), and the respiratory system (acute noncardiogenic pulmonary edema, pneumonitis). Thiazide diuretics may induce phototoxic dermatitis.[Ref]


Dermatologic reactions may indicate hypersensitivity to the drug. Erythema multiforme, Stevens-Johnson syndrome, exfoliative dermatitis (including toxic epidermal necrolysis), and alopecia have been associated with the use of thiazides in rare cases.[Ref]


More common gastrointestinal problems include gastric irritation, vomiting, cramping, nausea, anorexia, diarrhea, and constipation. Thiazide diuretics have been associated with acute cholecystitis, intrahepatic cholestasis with jaundice and rare cases of pancreatitis.[Ref]

A retrospective case-controlled drug surveillance study has revealed a relative risk of 2.0 for acute cholecystitis associated with the use of a thiazide. The suspected explanation for this association is the potentially deleterious effect that thiazides have on the serum lipid profile. Thiazide-induced hypercholesterolemia or hypertriglyceridemia may enhance the formation of some types of gallstones.[Ref]


Renal side effects including new or worsened renal insufficiency associated with benzthiazide therapy is a probable sign of intravascular volume depletion and serves as a signal to reduce or withhold therapy. Rare cases of allergic interstitial nephritis have been associated with the use of some thiazide diuretics.[Ref]


Endocrinologic changes associated with benzthiazide, as with other thiazide diuretic agents, include decreased glucose tolerance and a potentially deleterious effect on the lipid profile. These problems may be important in some patients with or who are at risk for diabetes or coronary artery disease.[Ref]

Nervous system

Nervous system-related complaints include dizziness, restlessness, paresthesia, headache, and xanthopsia.[Ref]


Hematologic side effects are rare. A few cases of immune-complex hemolytic anemia, aplastic anemia, agranulocytosis, leukopenia and thrombocytopenia have been associated with thiazide diuretics.[Ref]


Musculoskeletal cramping or spasms are occasionally reported during benzthiazide diuresis.[Ref]


1. Adler RA, Costanzo LS, Stauffer ME. Hypercalciuria in hyperprolactinemic rats: effects of benzthiazide. Metabolism. 1986;35:668-72.

2. Thompson RA, Crowley MF. Trial of a triamterene-benzthiazide combination (Dytide). Postgrad Med J. 1965;41:706-11.

3. Product Information. Exna (benzthiazide). Wyeth-Ayerst Laboratories. 2001;PROD.

4. Pickkers P, Schachter M, Hughes AD, Feher MD, Sever PS. Thiazide-induced hyperglycaemia: a role for calcium-activated potassium channels? Diabetologia. 1996;39:861-4.

Further information

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Some side effects may not be reported. You may report them to the FDA.