Bakris GL, Smith A
Effects of sodium intake on albumin excretion in
patients with diabetic nephropathy treated with long acting
calcium antagonists
Ann Int Med
(Aug) 125:201-204 1996

Whereas the proteinuria reducing effects of ACE inhibitors are well
documented, the effects of other drug classes remain somewhat
controversial. In this small study Bakris put 15 patients with NIDDM
on once-daily nifedipine, and then on once-daily diltiazem, and
studied the effects of these two CCBs on proteinuria. While on each
CCB, diet was also altered; there was a 4-week period of a 50 mEq/day
sodium diet and a 4-week period on a 250 mEq/day sodium diet.
Each drug reduced the diastolic BP from a mean of 101 to
about 80 mm Hg. However, nifedipine had no effect on urinary protein
excretion, which remained about 3 gm/day. Diltiazem lowered urinary
protein excretion by 50% on the low sodium diet, but had no
significant effect on the high sodium diet. The results suggest that
reductions in sodium intake, which are known to further reduce
proteinuria in patients taking ACE inhibitors, are of key importance
to the anti-proteinuric effects of diltiazem. The results are in
accord with a study in rats, suggesting that a low sodium diet
expresses a diltiazem-associated change in glomerular permeability
(Jyothirmay and Reddi, Hypertens 1993:21:795-802).
Comment: The unstated clinical implications seem to be:
CCBs are not a good drug for proteinuric hypertensive diabetics if one
goal is to reduce the amount of proteinuria. However, in diabetics
taking diltiazem, salt restriction may be of some additional benefit.
(John T. Daugirdas, M.D., University of Illinois at Chicago)