Calcium Channel Blockers
Calcium channel blockers prevent ischemic renal injury by a number
of mechanisms, including prevention of reflow-induced vasoconstriction after ischemia,
inhibition of angiotensin action in the glomerulus, and reduction of circulating
interleukin-2 receptors.[81]
They may reduce the
accumulation of oxygen free radicals and reperfusion injury through prevention of
intracellular calcium influx and the calcium/calmodulin-dependent conversion of xanthine
dehydrogenase to xanthine oxidase.
However, calcium blockers may overcome renal autoregulation and
worsen renal function when they induce hypotension. Administration of nifedipine
to patients with renal insufficiency has been reported to cause nonoliguric renal
failure that improved when use of the drug was discontinued.[82]
In contrast, in hypertensive patients, diltiazem and nifedipine promote natriuresis
and increase RBF and GFR.[83]
Calcium channel blockers confer important protection against nephrotoxins
such as cyclosporine, cisplatin, and radiocontrast dyes (see later).
