Losartan Potassium: In clinical trials, no drug interactions of clinical significance have been identified with hydrochlorothiazide, digoxin, warfarin, cimetidine, phenobarbital (phenobarbitone), ketoconazole and erythromycin. Rifampicin and fluconazole have been reported to reduce levels of active metabolite. The clinical consequences have not been evaluated.
As with other drugs that block angiotensin II or its effects, concomitant use of other drugs which retain potassium or may increase potassium levels (eg, potassium-sparing diuretics, potassium supplements or salt substitutes containing potassium) may lead to increases in serum potassium.
Hydrochlorothiazide: When given concurrently, the following drugs may interact with thiazide diuretics: Alcohol, Barbiturates or Narcotics: Potentiation of orthostatic hypotension may occur.
Antidiabetic Drugs (Oral Agents and Insulin): Dosage adjustment of the antidiabetic drug may be required.
Other Antihypertensive Drugs: There may be an additive effect.
Cholestyramine and Colestipol Resins: Absorption of hydrochlorothiazide is impaired in the presence of anionic exchanged resins.
Corticosteroids, Adrenocorticotropic Hormone (ACTH): There may be intensified electrolyte depletion, particularly hypokalemia.
Pressor Amines (eg, Adrenaline): Possible decreased response to pressor amines, but not sufficient to preclude their use.