PEARLS No. 230, February 2010, written by Brian R McAvoy

Clinical question

How effective are diuretics as second-line therapy for primary hypertension?  

Bottom line

Thiazides as a second-line drug reduced blood pressure (BP) by 6/3 and 8/4mmHg at doses of 1 and 2 times the manufacturerÕs recommended starting dose, respectively. Although the dose of hydrochlorothiazide (HCTZ) was studied over a wide range (5mg/ day to 45mg/day), a majority of the trials evaluated doses of 12.5mg/day and 25mg/day. The BP lowering effect was dose related. The effect seen was similar to that obtained when thiazides are used as a single agent. HCTZ was the thiazide used in 49 of 53 (92%) of the included studies. Only 3 double-blind randomised controlled trials (RCTs) evaluating loop diuretics were identified. These RCTs showed a BP lowering effect of about 6/3mmHg for a starting dose (piretanide 3mg/day and 6mg/day; frusemide 40mg/day).  

Caveat

Due to the short duration of the trials (3Ð12 weeks) and lack of reporting of adverse events, this review does not provide a good estimate of the incidence of adverse effects of diuretics given as a second-line blood pressure lowering drug treatment.

Context

Even with individualised monotherapy, BP targets are not likely to be achieved with the first drug used, even when titrated to high doses. Diuretics (thiazides and loop diuretics) are widely prescribed for hypertension, not only as a first-line drug treatment but also as a second-line treatment.

Cochrane Systematic Review

Chen JMH et al. Blood pressure lowering efficacy of diuretics as second-line therapy for primary hypertension. Cochrane Reviews 2009, Issue 4. Article No. CD007187. DOI: 10.1002/14651858. CD007187.pub2. This review contains 53 studies involving 15,129 participants.