Cilostazol (Page 2 of 4)

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of cilostazol tablets. Because these reactions are reported voluntarily from a population of an unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Blood and lymphatic system disorders:
Aplastic anemia, granulocytopenia, pancytopenia, bleeding tendency

Cardiac disorders:
Torsade de pointes and QTc prolongation in patients with cardiac disorders (e.g. complete atrioventricular block, heart failure; and bradyarrythmia), angina pectoris.

Gastrointestinal disorders:
Gastrointestinal hemorrhage, vomiting, flatulence, nausea

General disorders and administration site conditions:
Pain, chest pain, hot flushes

Hepatobiliary disorders:
Hepatic dysfunction/abnormal liver function tests, jaundice

Immune system disorders:
Anaphylaxis, angioedema, and hypersensitivity

Investigations:
Blood glucose increased, blood uric acid increased, increase in BUN (blood urea increased), blood pressure increase

Nervous system disorders:
Intracranial hemorrhage, cerebral hemorrhage, cerebrovascular accident, extradural hematoma and subdural hematoma

Renal and urinary disorders:
Hematuria

Respiratory, thoracic and mediastinal disorders:
Pulmonary hemorrhage, interstitial pneumonia

Skin and subcutaneous tissue disorders:
Hemorrhage subcutaneous, pruritus, skin eruptions including Stevens-Johnson syndrome, skin drug eruption (dermatitis medicamentosa), rash

Vascular disorders:
Subacute stent thrombosis, hypertension.

7 DRUG INTERACTIONS

7.1 Inhibitors of CYP3A4 or CYP2C19

Inhibitors of CYP3A4
Coadministration of strong (e.g., ketoconazole) and moderate (e.g., erythromycin, diltiazem and grapefruit juice) CYP3A4 inhibitors can increase exposure to cilostazol. Reduce cilostazol dose to 50 mg twice daily when coadministered with strong or moderate inhibitors of CYP3A4 [see Dosage and Administration ( 2.2) and Clinical Pharmacology ( 12.3)].

Inhibitors of CYP2C19
Coadministration with CYP2C19 inhibitors (e.g., omeprazole) increases systemic exposure of cilostazol active metabolites. Reduce cilostazol dose to 50 mg twice daily when coadministered with strong or moderate inhibitors of CYP2C19 [see Dosage and Administration ( 2.2) and Clinical Pharmacology ( 12.3)].

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Teratogenic Effects
Pregnancy Category C.

Cilostazol has been shown to be teratogenic in rats at doses that are greater than 5-times the human MRHD on a body surface area basis. There are no adequate and well-controlled studies in pregnant women.

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, 14 th 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).

8.3 Nursing Mothers

Transfer of cilostazol into milk has been reported in rats. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from cilostazol, discontinue nursing or discontinue cilostazol.

8.4 Pediatric Use

Safety and effectiveness of cilostazol in pediatric patients have not been established.

8.5 Geriatric Use

Of the total number of subjects (n = 2,274) in clinical studies of cilostazol, 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 excluded. Pharmacokinetic studies have not disclosed any age-related effects on the absorption, distribution, metabolism, and elimination of cilostazol and its metabolites.

8.6 Hepatic Impairment

No dose adjustment is required in patients with mild hepatic impairment. Patients with moderate or severe hepatic impairment have not been studied in clinical trials and dosing recommendations cannot be provided [see Clinical Pharmacology ( 12.3)].

8.7 Renal Impairment

No dose adjustment is required in patients with renal impairment. 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 to 98%) [see Clinical Pharmacology ( 12.3)].

10 OVERDOSAGE

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 patient should be carefully observed and given supportive treatment. Since cilostazol is highly protein-bound, it is unlikely that it can be efficiently removed by hemodialysis or peritoneal dialysis. The oral LD 50 of cilostazol is greater than 5 g per kg in mice and rats and greater than 2 g per kg in dogs.

11 DESCRIPTION

Cilostazol is a quinolinone derivative that inhibits cellular phosphodiesterase (more specific for phosphodiesterase III). The empirical formula of cilostazol is C 20 H 27 N 5 O 2 , and its molecular weight is 369.47. Cilostazol is 6-[4-(1-cyclohexyl-1 H -tetrazol-5-yl) butoxy]-3,4-dihydro-2(1 H)-quinolinone, CAS-73963-72-1.

Cilostazol occurs as white to off-white crystals or as a crystalline powder that is slightly soluble in methanol and ethanol, and is practically insoluble in water, 0.1 N HCl, and 0.1 N NaOH.

Cilostazol tablets, USP for oral administration are available in 50 mg and 100 mg round, white tablets. Each tablet, in addition to the active ingredient, contains the following inactive ingredients: corn starch, croscarmellose sodium, magnesium stearate, and silicon dioxide.

Meets USP Dissolution Test 2

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Cilostazol and several of its metabolites inhibit phosphodiesterase III activity and suppress cAMP degradation with a resultant increase in cAMP in platelets and blood vessels, leading to inhibition of platelet aggregation and vasodilation, respectively.

Cilostazol reversibly inhibits platelet aggregation induced by a variety of stimuli, including thrombin, ADP, collagen, arachidonic acid, epinephrine, and shear stress.

Cardiovascular effects:

Cilostazol affects both vascular beds and cardiovascular function. It produces heterogeneous dilation of vascular beds, with greater dilation in femoral beds than in vertebral, carotid or superior mesenteric arteries. Renal arteries were not responsive to the effects of cilostazol.

In dogs or cynomolgus monkeys, cilostazol increased heart rate, myocardial contractile force, and coronary blood flow as well as ventricular automaticity, as would be expected for a PDE III inhibitor. Left ventricular contractility was increased at doses required to inhibit platelet aggregation. A-V conduction was accelerated. In humans, heart rate increased in a dose-proportional manner by a mean of 5.1 and 7.4 beats per minute in patients treated with 50 and 100 mg twice daily, respectively.

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