Cilostazol Tablets, 50 mg and 100 mg

Rx only

Cilostazol is a quinolinone derivative that inhibits cellular phosphodiesterase (more specific for phosphodiesterase III). The molecular formula of cilostazol is

C₂₀H₂₇N₅O₂, and its molecular weight is 369.47. Cilostazol is 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone, CAS-73963-72-1. The structural formula is:

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 for oral administration are available in 50 mg and 100 mg round, white debossed tablets. Each tablet, in addition to the active ingredient, contains the following inactive ingredients: microcrystalline cellulose, pregelatinized starch, methylcellulose, carboxymethylcellulose calcium, and magnesium stearate.

The mechanism of the effects of cilostazol on the symptoms of intermittent claudication is not fully understood. 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, respectively.

Cilostazol reversibly inhibits platelet aggregation induced by a variety of stimuli, including thrombin, ADP, collagen, arachidonic acid, epinephrine, and shear stress. Effects on circulating plasma lipids have been examined in patients taking cilostazol tablets. After 12 weeks, as compared to placebo, cilostazol tablets 100 mg b.i.d. produced a reduction in triglycerides of 29.3 mg/dL (15%) and an increase in HDL-cholesterol of 4.0 mg/dL (≅10%).

Cilostazol tablets are absorbed after oral administration. A high fat meal increases absorption, with an approximately 90% increase in C_max and a 25% increase in AUC. Absolute bioavailability is not known. Cilostazol is extensively metabolized by hepatic cytochrome P-450 enzymes, mainly 3A4, 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.

Pharmacokinetics are approximately dose proportional. Cilostazol and its active metabolites have apparent elimination half-lives of about 11-13 hours. Cilostazol and its active metabolites accumulate about 2-fold with chronic administration and reach steady state blood levels within a few days. The pharmacokinetics of cilostazol and its two major active metabolites were similar in healthy normal subjects and patients with intermittent claudication due to peripheral arterial disease (PAD).

The mean ± SEM plasma concentration-time profile at steady state after multiple dosing of cilostazol 100 mg b.i.d. is shown below:

Cilostazol could have pharmacodynamic interactions with other inhibitors of platelet function and pharmacokinetic interactions because of effects of other drugs on its metabolism by CYP3A4 or CYP2C19. A reduced dose of cilostazol should be considered when taken concomitantly with CYP3A4 or CYP2C19 inhibitors. Cilostazol does not appear to inhibit CYP3A4 (see Pharmacokinetic and Pharmacodynamic Drug-Drug Interactions, Lovastatin).

Cilostazol tablets are indicated for the reduction of symptoms of intermittent claudication, as indicated by an increased walking distance.

Cilostazol and several of its metabolites are inhibitors of phosphodiesterase III. Several drugs with this pharmacologic effect have caused decreased survival compared to placebo in patients with class III-IV congestive heart failure.

Cilostazol tablets are contraindicated in patients with congestive heart failure of any severity.

Cilostazol tablets are contraindicated in patients with known or suspected hypersensitivity to any of its components.

Cilostazol tablets are contraindicated in patients with congestive heart failure. In patients without congestive heart failure, the long-term effects of PDE III inhibitors (including cilostazol) are unknown. Patients in the 3-6 month placebo-controlled trials of cilostazol were relatively stable (no recent myocardial infarction or strokes, no rest pain or other signs of rapidly progressing disease), and only 19 patients died (0.7% in the placebo group and 0.8% in the cilostazol group). The calculated relative risk of death of 1.2 has a wide 95% confidence limit (0.5-3.1). There are no data as to longer-term risk or risk in patients with more severe underlying heart disease.

There is no 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. Studies of concomitant use of cilostazol and clopidogrel are planned.

Please refer to the patient package insert.

Patients should be advised:

• to read the patient package insert for cilostazol tablets carefully before starting therapy and to reread it each time therapy is renewed in case the information has changed.
• to take cilostazol tablets at least one-half hour before or two hours after food.
• that the beneficial effects of cilostazol 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.
• about the uncertainty concerning cardiovascular risk in long-term use or in patients with severe underlying heart disease, as described under PRECAUTIONS.

Patients with moderate or severe hepatic impairment have not been studied in clinical trials.

Since cilostazol is extensively metabolized by cytochrome P-450 isoenzymes, caution should be exercised when cilostazol 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). Cilostazol tablets 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.

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 hemorrhage, hemosiderin deposition and fibrosis in the left ventricle, hemorrhage in the right atrial wall, hemorrhage 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 the 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.

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.

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 cilostazol tablets.

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

Of the total number of subjects (n=2274) 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 ruled out. Pharmacokinetic studies have not disclosed any age-related effects on the absorption, distribution, metabolism, and elimination of cilostazol and its metabolites.

Adverse events were assessed in eight placebo-controlled clinical trials involving 2274 patients exposed to either 50 or 100 mg b.i.d. cilostazol (n=1301) or placebo (n=973), with a median treatment duration of 127 days for patients on cilostazol and 134 days for patients on placebo.

The only adverse event resulting in discontinuation of therapy in ≥3% of patients treated with cilostazol 50 or 100 mg b.i.d. was headache, which occurred with an incidence of 1.3%, 3.5%, and 0.3% in patients treated with cilostazol 50 mg b.i.d., 100 mg b.i.d, or placebo, respectively. Other frequent causes of discontinuation included palpitation and diarrhea, both 1.1% for cilostazol (all doses) versus 0.1% for placebo.

The most commonly reported adverse events, occurring in ≥2% of patients treated with cilostazol 50 or 100 mg b.i.d., are shown in the table (to the right).

Other events seen with an incidence of ≥2% but occurring in the placebo group, at least as frequently as in the 100 mg b.i.d. group were: asthenia, hypertension, vomiting, leg cramps, hyperesthesia, paresthesia, dyspnea, rash, hematuria, urinary tract infection, flu syndrome, angina pectoris, arthritis, and bronchitis.

 Less frequent adverse events (<2%) that were experienced by patients exposed to cilostazol 50 mg b.i.d. or 100 mg b.i.d. in the eight controlled clinical trials and that occurred at a frequency in the 100 mg b.i.d. group greater than placebo, regardless of suspected drug relationship, are uled below.

Body as a whole: Chills, face edema, fever, generalized edema, malaise, neck rigidity, pelvic pain, retroperitoneal hemorrhage.

Cardiovascular: Atrial fibrillation, atrial flutter, cerebral infarct, cerebral ischemia, congestive heart failure, heart arrest, hemorrhage, hypotension, myocardial infarction, myocardial ischemia, nodal arrhythmia, postural hypotension, supraventricular tachycardia, syncope, varicose vein, vasodilation, ventricular extrasystoles, ventricular tachycardia.

Digestive: Anorexia, cholelithiasis, colitis, duodenal ulcer, duodenitis, esophageal hemorrhage, esophagitis, increased GGT, gastritis, gastroenteritis, gum hemorrhage, hematemesis, melena, peptic ulcer, periodontal abscess, rectal hemorrhage, stomach ulcer, tongue edema.

Endocrine: Diabetes mellitus. 

Hemic and Lymphatic: Anemia, ecchymosis, iron deficiency anemia, polycythemia, purpura.

Metabolic and Nutritional: Increased creatinine, gout, hyperlipemia, hyperuricemia.

Musculoskeletal: Arthralgia, bone pain, bursitis. 

Nervous: Anxiety, insomnia, neuralgia.

Respiratory: Asthma, epistaxis, hemoptysis, pneumonia, sinusitis. 

Skin and Appendages: Dry skin, furunculosis, skin hypertrophy, urticaria.

Special Senses: Amblyopia, blindness, conjunctivitis, diplopia, ear pain, eye hemorrhage, retinal hemorrhage, tinnitus.

Urogenital: Albuminuria, cystitis, urinary frequency, vaginal hemorrhage, vaginitis.

The following adverse events have been reported worldwide since the launch of cilostazol in the US: pain, chest pain, hot flushes, cerebral hemorrhage, angina pectoris, hypotension, hepatic dysfunction/abnormal liver function tests, jaundice, vomiting, thrombocytopenia, leukopenia, bleeding tendency, paresthesia, hyperglycemia, pulmonary hemorrhage, interstitial pneumonia, pruritus, skin eruptions including Stevens-Johnson syndrome, rash, increase in BUN, and hematuria.

The following adverse events occurred outside the US prior to marketing of cilostazol in the US: pulmonary hemorrhage and Stevens-Johnson syndrome.

Information on acute overdosage with cilostazol tablets 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 LD₅₀ of cilostazol is >5.0 g/kg in mice and rats and >2.0 g/kg in dogs.

The recommended dosage of cilostazol tablets is 100 mg b.i.d., taken at least half an hour before or two hours after breakfast and dinner. A dose of 50 mg b.i.d. should be considered during coadministration of such inhibitors of CYP3A4 as ketoconazole, itraconazole, erythromycin and diltiazem, and during coadministration of such inhibitors of CYP2C19 as omeprazole.

Patients may respond as early as 2 to 4 weeks after the initiation of therapy, but treatment for up to 12 weeks may be needed before a beneficial effect is experienced.

 The available data suggest that the dosage of cilostazol tablets can be reduced or discontinued without rebound (i.e., platelet hyperaggregability).

Cilostazol tablets are supplied as follows:

50 mg tablets: white, round, debossed with “” over “123” on one side and plain on the other, and provided in bottles of 60 and 500 tablets.

100 mg tablets: white, round, debossed with “” over “223” on one side and plain on the other, and provided in bottles of 60 and 500 tablets.

Store at 20° to 25°C (68° to 77° F) [see USP Controlled Room Temperature].

Sandoz Inc.

Princeton, NJ 08540

Rev. 10/06

MF0223REV10/06

OS8128