Pletal (cilostazol) is a quinolinone derivative that inhibits cellular phosphodiesterase (more specific for phosphodiesterase III). The empirical formula of cilostazol is C₂₀H₂₇N₅O₂, and its molecular weight is 369.46. 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.

Pletal (cilostazol) tablets for oral administration are available in 50 mg triangular and 100 mg round, white debossed tablets. Each tablet, in addition to the active ingredient, contains the following inactive ingredients: carboxymethylcellulose calcium, corn starch, hydroxypropyl methylcellulose 2910, magnesium stearate, and microcrystalline cellulose.

Last updated on RxList: 12/19/2007

Pletal is indicated for the reduction of symptoms of intermittent claudication, as indicated by an increased walking distance.

The recommended dosage of Pletal 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.

Discontinuation of Therapy: The available data suggest that the dosage of Pletal can be reduced or discontinued without rebound (i.e., platelet hyperaggregability).

Pletal is supplied as 50 mg and 100 mg tablets. The 50 mg tablets are white, triangular, debossed with Pletal 50, and provided in bottles of 60 tablets (NDC #59148-003-16).

The 100 mg tablets are white, round, debossed with Pletal 100, and provided in bottles of 60 tablets (NDC #59148-002-16).

Storage

Store Pletal tablets at 25°C (77°F); excursions permitted to 15-30°C (59-86°F) [See USP Controlled Room Temperature].

Manufactured for : Otsuka America Pharmaceutical, Inc. Rockville, MD 20850. Manufactured by : Otsuka America Pharmaceutical, Inc.Tokushima 771-0192, Japan. FDA revision date: 11/13/2007

Last updated on RxList: 12/19/2007

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

The only adverse event resulting in discontinuation of therapy in ≥ 3% of patients treated with Pletal 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 Pletal 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 Pletal 50 or 100 mg b.i.d., are shown in the table (below).

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, hypesthesia, paresthesia, dyspnea, rash, hematuria, urinary tract infection, flu syndrome, angina pectoris, arthritis, and bronchitis.

Most Commonly Reported AEs (Incidence ≥ 2%) in Patients on Pletal (PLT) 50 mg b.i.d. or 100 mg b.i.d. and Occurring at a Rate in the 100 mg b.i.d. Group Higher Than in Patients on Placebo

Adverse Events (AEs) by Body System	PLT 50 mg b.i.d. (N=303) %	PLT 100 mg b.i.d. (N=998) %	Placebo (N=973) %
BODY AS A WHOLE
Abdominal pain	4	5	3
Back pain	6	7	6
Headache	27	34	14
Infection	14	10	8
CARDIOVASCULAR
Palpitation	5	10	1
Tachycardia	4	4	1
DIGESTIVE
Abnormal stools	12	15	4
Diarrhea	12	19	7
Dyspepsia	6	6	4
Flatulence	2	3	2
Nausea	6	7	6
METABOLIC & NUTRITIONAL
Peripheral edema	9	7	4
MUSCULO-SKELETAL
Myalgia	2	3	2
NERVOUS
Dizziness	9	10	6
Vertigo	3	1	1
RESPIRATORY
Cough increased	3	4	3
Pharyngitis	7	10	7
Rhinitis	12	7	5

Less frequent adverse events ( < 2%) that were experienced by patients exposed to Pletal 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 in the placebo group, regardless of suspected drug relationship, are listed below.

Body as a whole: Chills, face edema, fever, generalized edema, malaise, neck rigidity, pelvic pain, retroperitoneal haemorrhage.
Cardiovascular: Atrial fibrillation, atrial flutter, cerebral infarct, cerebral ischemia, congestive heart failure, heart arrest, haemorrhage, 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 haemorrhage, esophagitis, increased GGT, gastritis, gastroenteritis, gum haemorrhage, hematemesis, melena, peptic ulcer, periodontal abscess, rectal haemorrhage, 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 haemorrhage, retinal haemorrhage, tinnitus.
Urogenital: Albuminuria, cystitis, urinary frequency, vaginal haemorrhage, vaginitis.

Post-Marketing Experience

The following events have been reported spontaneously from worldwide post-marketing experience since the launch of Pletal in the US.

• Blood and lymphatic system disorders:
  • Agranulocytosis, aplastic anemia, granulocytopenia, thrombocytopenia, leukopenia, bleeding tendency
• Cardiac disorders:
  • Torsades de pointes, QTc prolongation (torsades de pointes and QTc prolongation occurred in patients with cardiac disorders, e.g. complete atrioventricular block, cardiac failure and bradyarrythmia, when treated with cilostazol. Cilostazol was used “off label” due to its positive chronotropic action)
• Gastrointestinal disorders:
  • Gastrointestinal haemorrhage
• General disorders and administration site conditions:
  • Pain, chest pain, hot flushes
• Hepatobiliary disorders:
  • Hepatic dysfunction/abnormal liver function tests, jaundice
• Injury, poisoning and procedural complications:
  • Extradural haematoma and subdural haematoma
• Investigations:
  • Blood glucose increased, blood uric acid increased, platelet count decreased, white blood cell count decreased, increase in BUN (blood urea increased), blood pressure increase
• Nervous system disorders:
  • Intracranial haemorrhage, cerebral haemorrhage, cerebrovascular accident
• Respiratory, thoracic and mediastinal disorders:
  • Pulmonary haemorrhage, interstitial pneumonia
• Skin and subcutaneous tissue disorders:
  • Haemorrhage subcutaneous, pruritus, skin eruptions including Stevens-Johnson syndrome, skin drug eruption (dermatitis medicamentosa)
• Vascular disorders:
  • Subacute thrombosis (these cases of subacute thrombosis occurred in patients treated with aspirin and “off label” use of cilostazol for prevention of thrombotic complication after coronary stenting)

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.

Cardiovascular Toxicity

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.

Last updated on RxList: 12/19/2007

No information provided.

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.

Hepatic Impairment

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.

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 (95-98%).

Special caution is advised when Pletal is used in patients with severe renal impairment: estimated creatinine clearance < 25 ml/min.

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

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, 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).

There are no adequate and well-controlled studies in pregnant women.

Nursing Mothers

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.

Pediatric Use

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

Geriatric Use

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.

Last updated on RxList: 12/19/2007

Information on acute overdosage with Pletal 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.

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. Pletal is contraindicated in patients with congestive heart failure of any severity.

Pletal is contraindicated in patients with haemostatic disorders or active pathologic bleeding, such as bleeding peptic ulcer and intracranial bleeding. Pletal inhibits platelet aggregation in a reversible manner.

Pletal is contraindicated in patients with known or suspected hypersensitivity to any of its components.

Last updated on RxList: 12/19/2007

Mechanism of Action

The mechanism of the effects of Pletal on the symptoms of intermittent claudication is not fully understood. Pletal 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.

Pletal 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 Pletal. After 12 weeks, as compared to placebo, Pletal 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%).

Cardiovascular Effects

Cilostazol affects both vascular beds and cardiovascular function. It produces non-homogeneous 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 cynomolgous 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 b.i.d., respectively. In 264 patients evaluated with Holter monitors, numerically more cilostazol-treated patients had increases in ventricular premature beats and non-sustained ventricular tachycardia events than did placebo-treated patients; the increases were not dose-related.

Pharmacokinetics

Pletal 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. 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 Pletal. 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 Pletal 100 mg b.i.d. is shown below:

Distribution

Plasma Protein and Erythrocyte Binding

Cilostazol is 95 - 98% protein bound, predominantly to albumin. The mean percent binding for 3,4-dehydro-cilostazol is 97.4% and for 4´-trans-hydroxy-cilostazol is 66%. Mild hepatic impairment did not affect protein binding. The free fraction of cilostazol was 27% higher in subjects with renal impairment than in normal volunteers. The displacement of cilostazol from plasma proteins by erythromycin, quinidine, warfarin, and omeprazole was not clinically significant.

Metabolism and Excretion

Cilostazol is eliminated predominately by metabolism and subsequent urinary excretion of metabolites. Based on in vitro studies, the primary isoenzymes involved in cilostazol's metabolism are CYP3A4 and, to a lesser extent, CYP2C19. The enzyme responsible for metabolism of 3,4-dehydro-cilostazol, the most active of the metabolites, is unknown.

Following oral administration of 100 mg radiolabeled cilostazol, 56% of the total analytes in plasma was cilostazol, 15% was 3,4-dehydro-cilostazol (4-7 times as active as cilostazol), and 4% was 4´-trans-hydroxy-cilostazol (one fifth as active as cilostazol). 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. The remainder was excreted as other metabolites, none of which exceeded 5%. There was no evidence of induction of hepatic microenzymes.

Special Populations

Age and Gender

The total and unbound oral clearances, adjusted for body weight, of cilostazol and its metabolites were not significantly different with respect to age and/or gender across a 50-to-80-year-old age range.

Smokers

Population pharmacokinetic analysis suggests that smoking decreased cilostazol exposure by about 20%.

Hepatic Impairment

The pharmacokinetics of cilostazol and its metabolites were similar in subjects with mild hepatic disease as compared to healthy subjects.

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

Renal Impairment

The total pharmacologic activity of cilostazol and its metabolites was similar in subjects with mild to moderate renal impairment and in normal subjects. Severe renal impairment increases metabolite levels and alters protein binding of the parent and metabolites. The expected pharmacologic activity, however, based on plasma concentrations and relative PDE III inhibiting potency of parent drug and metabolites, appeared little changed. 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%).

Pharmacokinetic and Pharmacodynamic Drug-Drug Interactions

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 Pletal 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).

Aspirin

Short-term ( ≤ 4 days) coadministration of aspirin with Pletal increased the inhibition of ADP-induced ex vivo platelet aggregation by 22% - 37% when compared to either aspirin or Pletal alone. Short-term ( ≤ 4 days) coadministration of aspirin with Pletal increased the inhibition of arachidonic acid-induced ex vivo platelet aggregation by 20% compared to Pletal alone and by 48% compared to aspirin alone. However, short-term coadministration of aspirin with Pletal had no clinically significant impact on PT, aPTT, or bleeding time compared to aspirin alone. Effects of long-term coadministration in the general population are unknown. In eight randomized, placebo-controlled, double-blind clinical trials, aspirin was coadministered with cilostazol to 201 patients. The most frequent doses and mean durations of aspirin therapy were 75-81 mg daily for 137 days (107 patients) and 325 mg daily for 54 days (85 patients). There was no apparent increase in incidence of hemorrhagic adverse effects in patients taking cilostazol and aspirin compared to patients taking placebo and equivalent doses of aspirin.

Warfarin

The cytochrome P-450 isoenzymes involved in the metabolism of R-warfarin are CYP3A4, CYP1A2, and CYP2C19, and in the metabolism of S-warfarin, CYP2C9. Cilostazol did not inhibit either the metabolism or the pharmacologic effects (PT, aPTT, bleeding time, or platelet aggregation) of R- and S-warfarin after a single 25-mg dose of warfarin. The effect of concomitant multiple dosing of warfarin and Pletal on the pharmacokinetics and pharmacodynamics of both drugs is unknown.

Clopidogrel

Multiple doses of clopidogrel do not significantly increase steady state plasma concentrations of cilostazol.

Inhibitors of CYP3A4

Strong Inhibitors of CYP3A4: A priming dose of ketoconazole 400 mg (a strong inhibitor of CYP3A4), was given one day prior to coadministration of single doses of ketoconazole 400 mg and cilostazol 100 mg. This regimen increased cilostazol Cmax by 94% and AUC by 117%. Other strong inhibitors of CYP3A4, such as itraconazole, fluconazole, miconazole, fluvoxamine, fluoxetine, nefazodone, and sertraline, would be expected to have a similar effect (see DOSAGE AND ADMINISTRATION).

Moderate Inhibitors of CYP3A4

1. Erythromycin and other macrolide antibiotics: Erythromycin is a moderately strong inhibitor of CYP3A4. Coadministration of erythromycin 500 mg q 8h with a single dose of cilostazol 100 mg increased cilostazol Cmax by 47% and AUC by 73%. Inhibition of cilostazol metabolism by erythromycin increased the AUC of 4´-trans-hydroxy-cilostazol by 141%. Other macrolide antibiotics (e.g., clarithromycin), but not all (e.g., azithromycin), would be expected to have a similar effect (see DOSAGE AND ADMINISTRATION).
2. Diltiazem: Diltiazem 180 mg decreased the clearance of cilostazol by ~30%. Cilostazol Cmax increased ~30% and AUC increased ~40% (see DOSAGE AND ADMINISTRATION).
3. Grapefruit Juice: Grapefruit juice increased the Cmax of cilostazol by ~50%, but had no effect on AUC.

INHIBITORS OF CYP2C19

Omeprazole: Coadministration of omeprazole did not significantly affect the metabolism of cilostazol, but the systemic exposure to 3,4-dehydro-cilostazol was increased by 69%, probably the result of omeprazole's potent inhibition of CYP2C19 (see DOSAGE AND ADMINISTRATION).

Quinidine

Concomitant administration of quinidine with a single dose of cilostazol 100 mg did not alter cilostazol pharmacokinetics.

Lovastatin

The concomitant administration of lovastatin with cilostazol decreases cilostazol Css, max and AUCτ by 15%. There is also a decrease, although nonsignificant, in cilostazol metabolite concentrations. Coadministration of cilostazol with lovastatin increases lovastatin and β-hydroxi lovastatin AUC approximately 70%. This is most likely clinically insignificant.

Clinical Studies

The ability of Pletal to improve walking distance in patients with stable intermittent claudication was studied in eight large, randomized, placebo-controlled, double-blind trials of 12 to 24 weeks' duration using dosages of 50 mg b.i.d. (n=303), 100 mg b.i.d. (n=998), and placebo (n=973). Efficacy was determined primarily by the change in maximal walking distance from baseline (compared to change on placebo) on one of several standardized exercise treadmill tests.

Compared to patients treated with placebo, patients treated with Pletal 50 or 100 mg b.i.d. experienced statistically significant improvements in walking distances both for the distance before the onset of claudication pain and the distance before exercise-limiting symptoms supervened (maximal walking distance). The effect of Pletal on walking distance was seen as early as the first on-therapy observation point of two or four weeks.

The following figure depicts the percent mean improvement in maximal walking distance, at study end for each of the eight studies.

Across the eight clinical trials, the range of improvement in maximal walking distance in patients treated with Pletal 100 mg b.i.d., expressed as the percent mean change from baseline, was 28% to 100%.

The corresponding changes in the placebo group were -10% to 41%.

The Walking Impairment Questionnaire, which was administered in six of the eight clinical trials, assesses the impact of a therapeutic intervention on walking ability. In a pooled analysis of the six trials, patients treated with either Pletal 100 mg b.i.d. or 50 mg b.i.d. reported improvements in their walking speed and walking distance as compared to placebo. Improvements in walking performance were seen in the various subpopulations evaluated, including those defined by gender, smoking status, diabetes mellitus, duration of peripheral artery disease, age, and concomitant use of beta blockers or calcium channel blockers. Pletal has not been studied in patients with rapidly progressing claudication or in patients with leg pain at rest, ischemic leg ulcers, or gangrene. Its long-term effects on limb preservation and hospitalization have not been evaluated.

A randomized, double-blind, placebo-controlled Phase IV study was conducted to assess the long-term effects of cilostazol, with respect to mortality and safety, in 1,439 patients with intermittent claudication and no heart failure. The trial stopped early due to enrollment difficulties and a lower than expected overall death rate. With respect to mortality, the observed 36-month Kaplan-Meier event rate for deaths on study drug with a median time on study drug of 18 months was 5.6% (95% CI of 2.8 to 8.4 %) on cilostazol and 6.8% (95% CI of 1.9 to 11.5 %) on placebo. These data appear to be sufficient to exclude a 75% increase in the risk of mortality on cilostazol, which was the a priori study hypothesis.

Last updated on RxList: 12/19/2007

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.

Last updated on RxList: 12/19/2007

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

CILOSTAZOL - ORAL

(sill-OSS-tuh-zole)

COMMON BRAND NAME(S): Pletal

WARNING: Medications similar to cilostazol have shortened the lives of people with a certain type of heart disease (congestive heart failure). Therefore, do not use cilostazol if you have congestive heart failure.

USES: Cilostazol is used to reduce leg pain when walking and limping caused by blood circulation disease (peripheral vascular disease). This medication helps to increase your walking distance by improving blood and oxygen flow in the legs. It works by widening blood vessels in the legs and by blocking certain blood cells called platelets to prevent them from forming harmful blood clots.

OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This medication may also be used after certain types of heart procedures to prevent blood vessels from narrowing and harmful blood clots.

HOW TO USE: Take this medication by mouth, usually twice daily, at least 30 minutes before or 2 hours after breakfast and dinner, or as directed by your doctor. Dosage is based on your medical condition and response to therapy.

Use this medication regularly in order to get the most benefit from it. Remember to use it at the same times each day.

Avoid eating grapefruit or drinking grapefruit juice while being treated with this medication unless your doctor instructs you otherwise. Grapefruit juice can increase the amount of certain medications in your bloodstream. Consult your doctor or pharmacist for more details.

Your symptoms may improve in 2-4 weeks, but it may take up to 12 weeks to notice a benefit from this drug.

Inform your doctor if your condition persists or worsens.

SIDE EFFECTS: Headache, diarrhea, and dizziness may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these serious side effects occur: fast/pounding/irregular heartbeat, swelling of the hands/feet.

Tell your doctor immediately if any of these highly unlikely but very serious side effects occur: yellowing of the eyes/skin, easy bruising/bleeding, black or bloody stools, signs of infection (e.g., fever, persistent sore throat), cough with trouble breathing.

Seek immediate medical attention if any of these highly unlikely but very serious side effects occur: fainting, vision changes, weakness on one side of the body, slurred speech, confusion, chest pain.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching, swelling, severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking cilostazol, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: congestive heart failure, bleeding disorders (e.g., bleeding ulcers).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: other heart disease (e.g., recent heart attack, unstable angina, arrhythmias), recent stroke, kidney disease, liver disease, certain blood disorders (thrombocytopenia or low platelet counts).

Before having surgery, tell your doctor or dentist that you are taking this medication.

This drug may make you dizzy; use caution engaging in activities requiring alertness such as driving or using machinery. Limit alcoholic beverages.

This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.

It is not known if this medication passes into breast milk. Because of the potential risk to a nursing infant, breast-feeding while using this medication is not recommended. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with them first.

See also the How to Use section.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: "blood thinners" (e.g., heparin, warfarin), other "anti-platelet" drugs (e.g., clopidogrel, dipyridamole, ticlopidine), drugs affecting the removal of cilostazol from your system (CYP 3A4 and 2C19 substrates, inhibitors and inducers such as azole antifungals, macrolide antibiotics, diltiazem, nefazodone, SSRI antidepressants, cimetidine, rifamycins, St John's wort, certain anti-seizure medications, esomeprazole, omeprazole), tipranavir.

Check all prescription and nonprescription medicine labels carefully since many contain pain relievers/fever reducers (nonsteroidal anti-inflammatory drugs or NSAIDs such as ibuprofen, naproxen, or aspirin) which can increase the risk of bleeding/anti-platelet effect when used with cilostazol. Low-dose aspirin (usually 81-325 milligrams per day) as prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention should be continued. Consult your doctor or pharmacist for more details.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly. Symptoms of overdose may include: severe headache, very fast/ irregular heartbeat, or severe dizziness.

NOTES: Do not share this medication with others.

Laboratory and/or medical tests may be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

MISSED DOSE: If you miss a dose, use it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store at room temperature at 77 degrees F (25 degrees C) away from light and moisture. Brief storage between 59-86 degrees F (15-30 degrees C) is permitted. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For enrollment information call MedicAlert at 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.