Hematologic adverse reactions
Rare cases have been reported of thrombocytopenia or leukopenia progressing to agranulocytosis when cilostazol was not immediately discontinued. The agranulocytosis, however, was reversible on discontinuation of cilostazol.
Use with Clopidogrel
There is limited information with respect to the efficacy or safety of the concurrent use of cilostazol and clopidogrel, a platelet-aggregation inhibiting drug indicated for use in patients with peripheral arterial disease. Although it cannot be determined whether there was an additive effect on bleeding times during concomitant administration with cilostazol and clopidogrel, caution is advised for checking bleeding times during coadministration.
Information for Patients
Please refer to the patient package insert.
Patients should be advised:
- to read the patient package insert for PLETAL carefully before starting therapy and to reread it each time therapy is renewed in case the information has changed.
- to take PLETAL at least one-half hour before or two hours after food.
- that the beneficial effects of PLETAL on the symptoms of intermittent claudication may not be immediate. Although the patient may experience benefit in 2 to 4 weeks after initiation of therapy, treatment for up to 12 weeks may be required before a beneficial effect is experienced.
Patients with moderate or severe hepatic impairment have not been studied in clinical trials.
Special caution is advised when PLETAL is used in such patients.
Patients on dialysis have not been studied, but, it is unlikely that cilostazol can be removed efficiently by dialysis because of its high protein binding (95-98%).
Special caution is advised when PLETAL is used in patients with severe renal impairment: estimated creatinine clearance <25 ml/min.
Since PLETAL is extensively metabolized by cytochrome P-450 isoenzymes, caution should be exercised when PLETAL is coadministered with inhibitors of CYP3A4 such as ketoconazole and erythromycin or inhibitors of CYP2C19 such as omeprazole. Pharmacokinetic studies have demonstrated that omeprazole and erythromycin significantly increased the systemic exposure of cilostazol and/or its major metabolites. Population pharmacokinetic studies showed higher concentrations of cilostazol among patients concurrently treated with diltiazem, an inhibitor of CYP3A4 (see CLINICAL PHARMACOLOGY, Pharmacokinetic and Pharmacodynamic Drug-Drug Interactions). PLETAL does not, however, appear to cause increased blood levels of drugs metabolized by CYP3A4, as it had no effect on lovastatin, a drug with metabolism very sensitive to CYP3A4 inhibition.
Use with other antiplatelet agents
PLETAL inhibits platelet aggregation but in a reversible manner. Caution is advised in patients at risk of bleeding from surgery or pathologic processes. Platelet aggregability returns to normal within 96 hours of stopping PLETAL. Caution is advised in patients receiving both PLETAL and any other antiplatelet agent, or in patients with thrombocytopenia.
Repeated oral administration of cilostazol to dogs (30 or more mg/kg/day for 52 weeks, 150 or more mg/kg/day for 13 weeks, and 450 mg/kg/day for 2 weeks), produced cardiovascular lesions that included endocardial haemorrhage, hemosiderin deposition and fibrosis in the left ventricle, haemorrhage in the right atrial wall, haemorrhage and necrosis of the smooth muscle in the wall of the coronary artery, intimal thickening of the coronary artery, and coronary arteritis and periarteritis. At the lowest dose associated with cardiovascular lesions in the 52-week study, systemic exposure (AUC) to unbound cilostazol was less than that seen in humans at the maximum recommended human dose (MRHD) of 100 mg b.i.d. Similar lesions have been reported in dogs following the administration of other positive inotropic agents (including PDE III inhibitors) and/or vasodilating agents. No cardiovascular lesions were seen in rats following 5 or 13 weeks of administration of cilostazol at doses up to 1500 mg/kg/day. At this dose, systemic exposures (AUCs) to unbound cilostazol were only about 1.5 and 5 times (male and female rats, respectively) the exposure seen in humans at the MRHD. Cardiovascular lesions were also not seen in rats following 52 weeks of administration of cilostazol at doses up to 150 mg/kg/day. At this dose, systemic exposures (AUCs) to unbound cilostazol were about 0.5 and 5 times (male and female rats, respectively) the exposure in humans at the MRHD. In female rats, cilostazol AUCs were similar at 150 and 1500 mg/kg/day. Cardiovascular lesions were also not observed in monkeys after oral administration of cilostazol for 13 weeks at doses up to 1800 mg/kg/day. While this dose of cilostazol produced pharmacologic effects in monkeys, plasma cilostazol levels were less than those seen in humans given the MRHD, and those seen in dogs given doses associated with cardiovascular lesions.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Dietary administration of cilostazol to male and female rats and mice for up to 104 weeks, at doses up to 500 mg/kg/day in rats and 1000 mg/kg/day in mice, revealed no evidence of carcinogenic potential. The maximum doses administered in both rat and mouse studies were, on a systemic exposure basis, less than the human exposure at the MRHD of the drug. Cilostazol tested negative in bacterial gene mutation, bacterial DNA repair, mammalian cell gene mutation, and mouse in vivo bone marrow chromosomal aberration assays. It was, however, associated with a significant increase in chromosomal aberrations in the in vitro Chinese Hamster Ovary Cell assay.
Cilostazol did not affect fertility or mating performance of male and female rats at doses as high as 1000 mg/kg/day. At this dose, systemic exposures (AUCs) to unbound cilostazol were less than 1.5 times in males, and about 5 times in females, the exposure in humans at the MRHD.
Pregnancy Category C
In a rat developmental toxicity study, oral administration of 1000 mg cilostazol/kg/day was associated with decreased fetal weights, and increased incidences of cardiovascular, renal, and skeletal anomalies (ventricular septal, aortic arch and subclavian artery abnormalities, renal pelvic dilation, 14th rib, and retarded ossification). At this dose, systemic exposure to unbound cilostazol in nonpregnant rats was about 5 times the exposure in humans given the MRHD. Increased incidences of ventricular septal defect and retarded ossification were also noted at 150 mg/kg/day (5 times the MRHD on a systemic exposure basis). In a rabbit developmental toxicity study, an increased incidence of retardation of ossification of the sternum was seen at doses as low as 150 mg/kg/day. In nonpregnant rabbits given 150 mg/kg/day, exposure to unbound cilostazol was considerably lower than that seen in humans given the MRHD, and exposure to 3,4-dehydro-cilostazol was barely detectable.
When cilostazol was administered to rats during late pregnancy and lactation, an increased incidence of stillborn and decreased birth weights of offspring was seen at doses of 150 mg/kg/day (5 times the MRHD on a systemic exposure basis).
There are no adequate and well-controlled studies in pregnant women.
Transfer of cilostazol into milk has been reported in experimental animals (rats). Because of the potential risk to nursing infants, a decision should be made to discontinue nursing or to discontinue PLETAL.
The safety and effectiveness of PLETAL in pediatric patients have not been established.
Of the total number of subjects (n=2274) in clinical studies of PLETAL, 56 percent were 65-years-old and over, while 16 percent were 75-years-old and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out. Pharmacokinetic studies have not disclosed any age-related effects on the absorption, distribution, metabolism, and elimination of cilostazol and its metabolites.