Long Term Effects of Amlodipine on Renal Haemodynamics and Microalbuminuria in Patients with Essential Hypertension

In order to study the relationship between the long term renal haemodynamic effects of calcium antagonists and hypertensive renal damage, 8 patients with mild to moderate essential hypertension (6 males and 2 females, aged 19 to 60 years) underwent measurement of 24-hour microalbuminuria (urinary albumin excretion), mean blood pressure, effective renal plasma flow (para-aminohippuric acid clearance) and glomerular filtration rate (inulin clearance) before and after 12 to 16 months’ treatment with amlodipine 10mg once daily. Mean blood pressure fell from 125 ± 7mm Hg at baseline to 101 ± 3mm Hg during treatment with amlodipine (p < 0.001). Effective renal plasma flow did not change (633 ± 51 ml/min · 1.73m2 to 626 ± 46 ml/min · 1.73m2), while renal vascular resistance decreased from 8.5 ± 0.6 dyn · sec · cm−5 to 7.0 ± 0.4 dyn · sec · cm−5 (p = 0.01). Glomerular filtration rate rose significantly (109 ± 7 ml/min · 1.73m2 at baseline to 122 ± 4 ml/min · 1.73m2, p < 0.02 after amlodipine treatment) and urinary albumin excretion decreased from 17.4 ± 4.2 mg/24h to 7.2 ± 1.5 mg/24h (p < 0.05). Our findings show that long term treatment with amlodipine is followed by sustained renal vasodilation, an increase in glomerular filtration rate and, consequently, an increase in filtration fraction. However, despite the long term increase in glomerular filtration, urinary albumin excretion falls substantially. We suggest that long term renal protection afforded by amlodipine may occur independently of its effects on glomerular haemodynamics.