Moderate sodium restriction and diuretics in the treatment of hypertension

Using a cross-over type setup with 4 periods of 1 month each in 22 patients with mild, mostly essential hypertension, the antihypertensive action of the following therapeutic regimens were compared: (1) a regular diet and placebo (period RP), (2) a regular diet and 100 mg. hydrochlorothiazide and 100 mg. spironolactone (period RD), (3) a moderate sodium restriction and placebo (LP period), and (4) this diet together with the same diuretics (period LD). The diuretics or placebo were administered on a double blind basis, while the sodium restriction or regular sodium diet was prescribed in an open, but randomized system. The 24 hour urinary sodium averaged 191.1 ± 61.2 mEq. during the RP period and 92.8 ± 41.8 mEq. during the LP period.Compared to the RP period, the reduction in home blood pressures was more important with diuretics alone ($\text{16.1}\text{8.1}$ mm. Hg) than with this moderate sodium restriction alone ($\text{7.7}\text{4.4}$ mm. Hg), while the combination of both produced a statistically significantly (p < 0.005) higher blood pressure reduction ($\text{20.7}\text{10.8}$ mm. Hg).Not only the diuretics but also the sodium restriction increased the serum uric acid, and this could be related to the decreased urinary uric acid clearance.A significant (p < 0.001) correlation (r = 0.66) was obtained between the decrease in systolic blood pressure (expressed in mm. Hg) produced by the sodium restriction (y) and the decrease in 24 hour urinary sodium excretion (expressed in mEq.) produced by the same diet:

$\text{y=?6.58+0.163}\text{x}$

These data suggest that a reduction of the daily NaCl intake from 10 to 5 Gm. could produce a decrease of blood pressure of about $\text{10}\text{5}$ mm. Hg.