The diuretic triamterene, which is often used in combination with hydrochlorothiazide (HCTZ) for the treatment of hypertension, appears to enhance the effect of HCTZ in lowering blood pressure (BP) in addition to its potassium-sparing action. The results of this research have been published in the Journal of General Internal Medicine.

In this observational study using electronic medical records from the Indiana Network for Patient Care of 17,291 patients with hypertension who were prescribed hydrochlorothiazide with or without triamterene between 2004–2012, BP outcomes were compared between patients taking HCTZ, with or without triamterene, either alone or in combination with other antihypertensive drugs. A propensity score analysis was used to assess the estimated effects.

Patients receiving triamterene plus HCTZ group lowered their systolic BP by 3.8mmHg more than those receiving only HCTZ (P<0.0001). Systolic BP was similarly lower for patients taking triamterene with other medication combinations and was consistently observed for different medication combinations. Depending on the concurrently used medications, the range of systolic BP reduction was between 1–4mmHg.

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“It is unlikely that a large clinical trial would be conducted to reexamine the blood pressure effect of triamterene, a drug that has been on the market since 1965. Yet smaller clinical trials simply do not provide sufficient power to determine the drug’s effect. Observational studies based on big data, like ours, provide a viable alternative,” said Wanzhu Tu, PhD, first author of the new study. Dr. Tu is a Regenstrief Institute investigator, an Indiana University Center for Aging Research scientist and a professor of biostatistics at the Indiana University School of Medicine.

The authors note that triamterene’s ability to lower BP in addition to its potassium-sparing action should be evaluated in future research.

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