Antiadrenergic antihypertensive drugs: their effect on renal function.

Peripheral alpha antagonists not only preserve renal hemodynamics, but decrease RVR and maintain renal perfusion autoregulation in the face of decreased systemic perfusion pressures. On the other hand, central alpha agonists appear to have variable effects. Clonidine preserves RBF and GFR both acutely and chronically, guanabenz decreases RBF acutely but not chronically, and alpha-methyl dopa preserved RBF but decreases GFR. Beta blockers also have variable effects on RBF: the most-often-studied beta blocker, propranolol, has reduced RBF by 10-20% while other commonly used beta blockers, such as nadolol and metoprolol, may preserve RBF. This may reflect propranolol's inability to maintain renal perfusion autoregulation in the face of decreased systemic blood pressure. This failure of propranolol is not completely understood but may be a function of its lack of cardioselectivity or ISA (49). It is also possible that inhibition of renal vasodilators such as the kallikrein-kinin system plays a role (49). Finally, it appears that patients with normal renal vascular tone may be at highest risk to suffer decrements in RBF with beta blockers. Perhaps most importantly, the clinical impact of propranolol's effect on renal function is unclear, since the reductions in GFR have not been sufficient to produce azotemia.