Cilostazol !

An oral phosphodiesterase III inhibitor that relaxes leg arteries and calms platelets. It increases walking distance in claudication.

Updated 2026-11-01

Class: Antiplatelet drugs
Enzyme: Phosphodiesterase 3 (PDE3)
ATC code: B01AC23

Phosphodiesterase 3 (PDE3)Cilostazol

The figure shows the catalytic domain of human PDE3B with IBMX, a non-selective phosphodiesterase inhibitor in the same active site; there is no structure with cilostazol.

Target in 3D: Phosphodiesterase 3 (PDE3). PDB structure 1SOJ (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Cilostazol and several of its metabolites inhibit phosphodiesterase III, the enzyme that breaks down cyclic AMP in platelets and vascular smooth muscle. More cAMP in platelets inhibits aggregation; more cAMP in vessel walls causes vasodilation. Together these improve blood flow to the legs during walking.

Cilostazol inhibits phosphodiesterase III
cAMP rises in platelets and in vessel walls
Platelets aggregate less and leg arteries dilate

Pharmacokinetics

Absorption: Absorbed by mouth; a high-fat meal increases absorption.
Distribution: 95 to 98% bound to plasma proteins, mostly albumin.
Metabolism: Extensively in the liver, mainly by CYP3A4 and to a lesser degree CYP2C19; some metabolites are active.
Elimination: Mainly as metabolites in the urine, the rest in the faeces.
Half-life: About 11 to 13 hours for cilostazol and its active metabolites.
Onset and duration: Walking may improve after 2 to 4 weeks, but up to 12 weeks may be needed.

Indications

Reduction of the symptoms of intermittent claudication, increasing walking distance. Peripheral artery disease →

Adverse effects

Common

Headache
Diarrhoea and abnormal stools
Palpitations and fast heart rate
Dizziness

Contraindications

Heart failure of any severity
Hypersensitivity to cilostazol

Key interactions

CYP3A4 inhibitors (ketoconazole, itraconazole, erythromycin, diltiazem): Raise cilostazol exposure; the regimen is reduced.
CYP2C19 inhibitors (omeprazole, fluconazole, ticlopidine): Raise exposure to an active metabolite; the regimen is reduced.
Other antiplatelets and anticoagulants: May add to bleeding risk; avoided in bleeding disorders or active bleeding.

What is monitored

Symptoms and signs of heart failure before and during treatment
Heart rate and palpitations
Platelet and white cell counts
Walking distance after several weeks

Administration and safety

Oral, taken at least half an hour before or two hours after breakfast and dinner
Heart failure is ruled out before the first dose (boxed warning)
Avoided in active bleeding or bleeding disorders

Nursing care

Ask about breathlessness, swollen legs or known heart failure before starting
Explain that headache and loose stools are common, and that benefit takes weeks
Report a fast or irregular heartbeat, chest pain, fever or sore throat
Check the medication list for CYP3A4 and CYP2C19 inhibitors

Pregnancy and breastfeeding

It caused malformations in rats and human data are lacking; it is generally avoided in pregnancy.

Test yourself

Think of the answer, then tap the question to see it.

What is cilostazol used for?

To reduce the symptoms of intermittent claudication from peripheral arterial disease, increasing walking distance.

Which condition contraindicates cilostazol, and why?

Heart failure of any severity: other PDE III inhibitors lowered survival in people with advanced heart failure.

How does cilostazol both dilate vessels and inhibit platelets?

By inhibiting phosphodiesterase III, it raises cAMP in vascular smooth muscle (vasodilation) and in platelets (less aggregation).

Add to my cards (3)

Peripheral artery disease

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - CILOSTAZOL tablet (DailyMed (U.S. National Library of Medicine), 2026); Cilostazol: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2024); 1SOJ: CATALYTIC DOMAIN OF HUMAN PHOSPHODIESTERASE 3B IN COMPLEX WITH IBMX (RCSB Protein Data Bank, 2004).

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Representative model, for educational purposes only.