Effects of nifedipine on renal responses to several diuretic agents in rats

Abstract

The influence of the dihydropyridine calcium antagonist nifedipine has been studied on the diuretic response to frusemide, acetazolamide and hydrochlorothiazide in water-loaded (25 mL kg-1) conscious rats. Oral administration of nifedipine (10 mg kg-1) markedly inhibited frusemide- and hydrochlorothiazide-induced diuresis as evidenced by a reduction in 5 h urine volume and urinary sodium and potassium elimination. However, it neither significantly enhanced nor limited urine and electrolyte excretion promoted by acetazolamide. Nifedipine, 5 and 10 mg kg-1 but not 1 mg kg-1, significantly (P less than 0.05) inhibited the diuretic response of hydrochlorothiazide. At doses which affect hydrochlorothiazide diuresis (5 and 10 mg kg-1), nifedipine was found to depress the mean arterial pressure by 32% in normotensive rats. These results are of interest in view of the often reported clinical side effect of nifedipine in promoting peripheral oedema in hypertensive patients and its use in combination with a thiazide or loop diuretic.

An orally active adenosine A1 receptor antagonist, FK838, increases renal excretion and maintains glomerular filtration rate in furosemide‐resistant rats

“…These responses were compared to the renal excretory responses in rats gavaged with either vehicle (0.5% methyl cellulose, n =26), FURO (1, 3, 10, 30, 100 mg kg −1 , n =12 each dose), or HCTZ (0.03, 0.3, 3, 30, 100 mg kg −1 , n =12 each dose). The protocol for the acute evaluation of oral diuretic agents in normal rats has been previously published (Rao & Fonteles, 1991; Humphrey, 1995). Briefly, all rats were housed in metabolic cages (two rats/cage) for at least 2 days prior to study for acclimitization.…”

Nifedipine-morphine interaction: a further investigation on nociception and locomotor activity in mice

“…In this case, nifedipine (or hydralazine) and morphine might exert a synergistic reduction in blood pressure, which may account for the behavioural depression. It must be noted that nifedipine (duodenal application) significantly decreased blood pressure in normotensive rats, even at the dose of 5 mg kg-' (Rao & Fonteles 1991), and that the hypotensive effects induced by verapamil, another calcium antagonist, were potentiated by a dose of morphine that, if given alone, produced only a minor reduction of arterial blood pressure (Della Puppa et al 1989). The hypothesis that a fall in blood pressure may play a role in the strong reduction of locomotor activity, induced by combinations of nifedipine and morphine in DBA mice, is supported by previous findings suggesting that circulatory changes may be involved in the behavioural interaction of the calcium antagonist with drugs affecting blood pressure, such as barbiturates at hypnotic doses (Sansone et al 1992).…”