Abstract

Objective: This prospective, randomised, double blind, placebo controlled, crossover study examined the effects of sodium chloride (NaCl) supplementation on the antialbuminuric action of telmisartan ± hydrochlorothiazide (HCT) in hypertensive patients with type 2 diabetes, increased albumin excretion rate (AER) and habitual low dietary salt intake (LDS, <100 mmol sodium/24 hr on 2/3 consecutive occasions) or high dietary salt intake (HDS, >200 mmol sodium/24 hr on 2/3 consecutive occasions).

Research design and methods: Following a washout period, subjects (n= 32) received telmisartan 40 mg/day for 4 weeks followed by telmisartan 40 mg plus HCT 12.5 mg/day for 4 weeks. For the last 2 weeks of each treatment period, patients received either NaCl 100 mmol/day or placebo capsules. After a second washout, the regimen was repeated with supplements in reverse order. AER and ambulatory blood pressure were measured at weeks 0, 4, 8, 14, 18 and 22.

Results: In LDS, NaCl supplementation reduced the antialbuminuric effect of telmisartan ± HCT from 42.3% (placebo) to 9.5% (p=0.004). By contrast, in HDS, NaCl supplementation did not reduce the AER response to telmisartan ± HCT (placebo 30.9%, NaCl 28.1%, p= 0.7). Changes in AER were independent of changes in blood pressure.

Conclusions: The AER response to telmisartan ± HCT under habitual low salt intake can be blunted by NaCl supplementation. By contrast, when there is already a suppressed RAAS under habitual high dietary salt intake, the additional NaCl does not alter the AER response.