Pharmacology Of Cilostazol

Indication	For the reduction of symptoms of intermittent claudication (pain in the legs that occurs with walking and disappears with rest).
Pharmacodynamics	Cilostazol is a quinolinone derivative indicated for the reduction of symptoms of intermittent claudication, as indicated by an increased walking distance. Intermittent claudication is pain in the legs that occurs with walking and disappears with rest. The pain occurs due to reduced blood flow to the legs.
Mechanism of action	Cilostazol and several of its metabolites are cyclic AMP (cAMP) phosphodiesterase III inhibitors (PDE III inhibitors), inhibiting phosphodiesterase activity and suppressing cAMP degradation with a resultant increase in cAMP in platelets and blood vessels, leading to inhibition of platelet aggregation and vasodilation.
Absorption	Cilostazol is absorbed after oral administration. A high fat meal increases absorption, with an approximately 90% increase in Cmax and a 25% increase in AUC. Absolute bioavailability is not known.
Volume of distribution	Not Available
Protein binding	95-98%
Metabolism	Hepatic. Cilostazol is extensively metabolized by hepatic cytochrome P-450 enzymes, mainly 3A4, and, to a lesser extent, 2C19, with metabolites largely excreted in urine. Two metabolites are active, with one metabolite appearing to account for at least 50% of the pharmacologic (PDE III inhibition) activity after administration of cilostazol.
Route of elimination	Cilostazol is extensively metabolized by hepatic cytochrome P-450 enzymes, mainly 3A4, and, to a lesser extent, 2C19, with metabolites largely excreted in urine. Cilostazol is eliminated predominately by metabolism and subsequent urinary excretion of metabolites. The primary route of elimination was via the urine (74%), with the remainder excreted in feces (20%). No measurable amount of unchanged cilostazol was excreted in the urine, and less than 2% of the dose was excreted as 3,4-dehydro-cilostazol. About 30% of the dose was excreted in urine as 4'-trans-hydroxy-cilostazol.
Half life	11-13 hours.
Clearance	Not Available
Toxicity	Information on acute overdosage with cilostazol in humans is limited. The signs and symptoms of an acute overdose can be anticipated to be those of excessive pharmacologic effect: severe headache, diarrhea, hypotension, tachycardia, and possibly cardiac arrhythmias. The oral LD50 of cilostazol is >5.0 g/kg in mice and rats and >2.0 g/kg in dogs.