The natriuretic effect of nifedipine gastrointestinal therapeutic system remains despite the presence of mild-to-moderate renal failure.

BACKGROUND

Calcium channel blockers facilitate the renal excretion of sodium and this effect is maintained during chronic administration of these drugs. However, it is unknown whether this natriuretic effect remains despite the presence of a decreased renal function.

OBJECTIVE

To compare the natriuretic capacity of nifedipine gastrointestinal therapeutic system (GITS) and lisinopril in patients with mild-to-moderate chronic renal failure.

METHODS

An open-label, randomized, comparative study was conducted to compare the natriuretic capacity of nifedipine GITS and lisinopril in the presence of mild-to-moderate renal failure (creatinine clearance 30-80 ml/min). After a wash-out period of 4 weeks an intravenous saline infusion (30 ml/kg of body weight of isotonic saline in 4 h) was performed and repeated after 4 weeks of active therapy. Two sex- and age-matched groups of hypertensive patients (n = 25) were included in the study. Renal failure was diagnosed as secondary to nephrosclerosis in all the patients.

RESULTS

A significant increase in the renal capacity to excrete the sodium load was observed in patients receiving nifedipine GITS (n = 11) but not in those taking lisinopril (n = 13). Both drugs controlled blood pressure to a similar extent. No changes were observed in body weight, glomerular filtration rate and renal plasma flow (measured as inulin and paraaminohippurate clearances). A significant drop was observed in urinary albumin excretion after lisinopril, but not after nifedipine. Heart rate was higher in nifedipine group.

CONCLUSION

The natriuretic capacity of nifedipine GITS remains despite the presence of mild-to-moderate chronic renal failure. Such an effect takes place in the absence of changes in renal hemodynamics, suggesting that it is caused by a direct tubular effect.