Hydrochlorothiazide increases blood levels of dofetilide (Tikosyn), increasing the adverse effects of dofetilide.

Hydrochlorothiazide reduces the elimination of lithium (Lithobid) by the kidneys, increasing blood levels of lithium and lithium toxicity. Nonsteroidal antiinflammatory drugs, for example, ibuprofen, may reduce the blood pressure-reducing effects of triamterene/hydrochlorothiazide.

Blood sugar levels can be elevated by hydrochlorothiazide necessitating adjustment in the doses of medications that are used for treating diabetes.

PREGNANCY: Triamterene/hydrochlorothiazide has not been adequately studied in pregnant women.

NURSING MOTHERS: Triamterene/hydrochlorothiazide has not been evaluated in nursing mothers. Hydrochlorothiazide is excreted in breast milk. There is some evidence that it may reduce production of breast milk.

SIDE EFFECTS: Side effects of triamterene/hydrochlorothiazide include abdominal pain, nausea, vomiting, rash, headache, dizziness, constipation, low blood pressure, electrolyte disturbance (for example, high potassium levels), muscle cramps, hypersensitivity, pancreatitis, and jaundice. Triamterene/hydrochlorothiazide may increase blood sugar (glucose) levels and precipitate or worsen diabetes. Patients allergic to sulfa drugs may also be allergic to hydrochlorothiazide because of the similarity in the chemical structure of the two drugs.

Reference: FDA Prescribing Information