Drug Interactions Agents Increasing Serum Potassium Coadministration of quinapril and hydrochlorothiazide with other drugs that raise serum potassium levels may result in hyperkalemia. Because renal clearance of lithium is reduced by thiazides, the risk of lithium toxicity is presumably raised further when, as in therapy with quinapril and hydrochlorothiazide, a thiazide diuretic is coadministered with the ACE inhibitor. Quinapril and hydrochlorothiazide and lithium should be coadministered with caution, and frequent monitoring of serum lithium levels is recommended.
Source: FDA drug label - quinapril hydrochloride/hydrochlorothiazide