Does Triamterene Enhance Hydrochlorothiazide's Hypotensive Effect?

To mitigate the hypokalemic effects of hydrochlorothiazide (HCTZ), the drug is available in combination with the potassium-sparing diuretic triamterene (combination products are Dyazide, Maxzide, and generics). However, whether triamterene also enhances HCTZ's hypotensive effect is unclear. Researchers addressed this question in an observational analysis of electronic records serving a healthcare network in metropolitan Indianapolis. About 3000 HCTZ recipients who also received triamterene were compared with about 14,000 HCTZ recipients who did not; propensity-score analysis was performed to adjust for background differences in the two groups.

When HCTZ was used without other blood pressure (BP)–lowering drugs, mean BP was significantly lower with HCTZ/triamterene than with HCTZ alone (by 4 mm Hg systolic and 1 mm Hg diastolic). When HCTZ was used with other drug classes (e.g., angiotensin-converting–enzyme inhibitors, calcium-channel blockers, β-blockers), addition of triamterene was associated with smaller — albeit still statistically significant — mean differences in systolic BP (2–3 mm Hg lower).