Impact of cilostazol on intimal proliferation after directional coronary atherectomy

The effect of cilostazol on the platelet-derived growth factor-beta/beta isoform reduction on venous hyperplasia in an experimental balloon-induced injury model

BACKGROUND

Intimal hyperplasia is the response to endothelial injury. Platelet-derived growth factor is released early and favors the formation of intimal hyperplasia. Although multiple treatments, from open surgery to endovascular techniques, have been used they remain controversial. There is currently interest in developing pharmacological strategies to address this pathology. Local vascular inflammation induced by vessel barotrauma generates intimal hyperplasia due to mechanical stress over the venous endothelium. Cilostazol is a selective phosphodiesterase type 3 (PDE3) selective inhibitor with a regulatory effect over intimal hyperplasia. The objective was to investigate cilostazol's role in inhibiting smooth muscle cell proliferation due to changes in the expression and release of PDGF-BB isoform and the effect on developing IH using an experimental model of vascular barotrauma (balloon-induced injury model).

METHODS

We included 12 New Zealand rabbits. The balloon-induced injury model (BIIM) and experimental group cilostazol (20 mg/kg/day) included 6 rabbits each. Contralateral veins from 6 rabbits used in BIIM model has been taken as control group. We measured and compared the expression of PDGF-BB and the development of IH. A pathologist board chooses a PDGFRα antibody to localized its expression by immunohistochemistry analysis. Subsequently, using an automated immunohistochemical staining machine, the PDGFR expression was evaluated using a Zeiss Primo Star 4 light microscope.

RESULTS

The measurement obtained in the intimal layer was: 126.12 μm2 in the CG, 232 μm2 in the BIIM group, and 178 μm2 in the EG. A statistically significant difference was observed. Baseline serum concentrations of PDGF-BB in the BIIM group were 0.22 pg/mL. At 12 h 0.42 pg/mL, and 0.17 pg/mL at seven days. In the experimental group, the basal levels were 0.33 pg/mL. With the use of cilostazol, a lower peak was obtained at 12 h (0.08 pg/mL). This difference was statistically significant.

CONCLUSIONS

Cilostazol induced a significant reduction of IH caused by barotrauma in the venous endothelium, which correlates with decrease in the PDGF-BB in serum. This could be attributed to the pharmacologic effect on PDGFR expression.

Preliminary Phytochemical Screening, In Vitro Antidiabetic, Antioxidant Activities, and Toxicity of Leaf Extracts of Psychotria malayana Jack

Psychotria malayana Jack belongs to the Rubiacea and is widespread in Southeast Asian countries. It is traditionally used to treat diabetes. Despite its potential medicinal use, scientific proof of this pharmacological action and the toxic effect of this plant are still lacking. Hence, this study aimed to investigate the in vitro antidiabetic and antioxidant activities, toxicity, and preliminary phytochemical screening of P. malayana leaf extracts by gas chromatography-mass spectrometry (GC-MS) after derivatization. The antidiabetic activities of different extracts of this plant were investigated through alpha-glucosidase inhibitory (AGI) and 2-NBDG glucose uptake using 3T3-L1 cell line assays, while the antioxidant activity was evaluated using DPPH and FRAP assays. Its toxicological effect was investigated using the zebrafish embryo/larvae (Danio rerio) model. The mortality, hatchability, tail-detachment, yolk size, eye size, beat per minute (BPM), and body length were taken into account to observe the teratogenicity in all zebrafish embryos exposed to methanol extract. The LC50 was determined using probit analysis. The methanol extract showed the AGI activity (IC50 = 2.71 ± 0.11 μg/mL), insulin-sensitizing activity (at a concentration of 5 µg/mL), and potent antioxidant activities (IC50 = 10.85 μg/mL and 72.53 mg AAE/g for DPPH and FRAP activity, respectively). Similarly, the water extract exhibited AGI activity (IC50 = 6.75 μg/mL), insulin-sensitizing activity at the concentration of 10 μg/mL, and antioxidant activities (IC50 = 27.12 and 33.71 μg/mL for DPPH and FRAP activity, respectively). The methanol and water extracts exhibited the LC50 value higher than their therapeutic concentration, i.e., 37.50 and 252.45 µg/mL, respectively. These results indicate that both water and methanol extracts are safe and potentially an antidiabetic agent, but the former is preferable since its therapeutic index (LC50/therapeutic concentration) is much higher than for methanol extracts. Analysis using GC-MS on derivatized methanol and water extracts of P. malayana leaves detected partial information on some constituents including palmitic acid, 1,3,5-benzenetriol, 1-monopalmitin, beta-tocopherol, 24-epicampesterol, alpha-tocopherol, and stigmast-5-ene, that could be a potential target to further investigate the antidiabetic properties of the plant. Nevertheless, isolation and identification of the bioactive compounds are required to confirm their antidiabetic activity and toxicity.

Update on Cilostazol: A Critical Review of Its Antithrombotic and Cardiovascular Actions and Its Clinical Applications

Cilostazol, a phosphodiesterase III inhibitor, has vasodilating and antiplatelet properties with a low rate of bleeding complications. It has been used over the past 25 years for improving intermittent claudication in patients with peripheral artery disease (PAD). Cilostazol also has demonstrated efficacy in patients undergoing percutaneous revascularization procedures for both PAD and coronary artery disease. In addition to its antithrombotic and vasodilating actions, cilostazol also inhibits vascular smooth muscle cell proliferation via phosphodiesterase III inhibition, thus mitigating restenosis. Accumulated evidence has shown that cilostazol, due to its "pleiotropic" effects, is a useful, albeit underutilized, agent for both coronary artery disease and PAD. It is also potentially useful after ischemic stroke and is an alternative in those who are allergic or intolerant to classical antithrombotic agents (eg, aspirin or clopidogrel). These issues are herein reviewed together with the pharmacology and pharmacodynamics of cilostazol. Large studies and meta-analyses are presented and evaluated. Current guidelines are also discussed, and the spectrum of cilostazol's actions and therapeutic applications are illustrated.

Cilostazol attenuates intimal hyperplasia in a mouse model of chronic kidney disease

Intimal hyperplasia (IH) is a common cause of vasculopathy due to direct endothelial damage (such as post-coronary revascularization) or indirect injury (such as chronic kidney disease, or CKD). Although the attenuation of coronary revascularization-induced IH (direct-vascular-injury-induced IH) by cilostazol, a phosphodiesterase III inhibitor, has been demonstrated, our understanding of the effect on CKD-induced IH (indirect-vascular-injury-induced IH) is limited. Herein, we tested if cilostazol attenuated CKD-induced IH in a mouse model of ischemic-reperfusion injury with unilateral nephrectomy (Chr I/R), a normotensive non-proteinuria CKD model. Cilostazol (50 mg/kg/day) or placebo was orally administered once daily from 1-week post-nephrectomy. At 20 weeks, cilostazol significantly attenuated aortic IH as demonstrated by a 34% reduction in the total intima area with 50% and 47% decreases in the ratios of tunica intima area/tunica media area and tunica intima area/(tunica intima + tunica media area), respectively. The diameters of aorta and renal function were unchanged by cilostazol. Interestingly, cilostazol decreased miR-221, but enhanced miR-143 and miR-145 in either in vitro or aortic tissue, as well as attenuated several pro-inflammatory mediators, including asymmetrical dimethylarginine, high-sensitivity C-reactive protein, vascular endothelial growth factor in aorta and serum pro-inflammatory cytokines (IL-6 and TNF-α). We demonstrated a proof of concept of the effectiveness of cilostazol in attenuating IH in a Chr I/R mouse model, a CKD model with predominantly indirect-vascular-injury-induced IH. These considerations warrant further investigation to develop a new primary prevention strategy for CKD-related IH.

Cilostazol reduces restenosis after carotid artery stenting

BACKGROUND

Although carotid artery stenting (CAS) has been proposed as an alternative to carotid endarterectomy in cerebral revascularization, restenosis remains an unsolved issue. Cilostazol is a unique antiplatelet drug that has vasodilatory effects and inhibits smooth muscle cell proliferation. We investigated whether cilostazol reduces restenosis after CAS.

METHODS

A database of 113 consecutive CAS procedures between April 2002 and December 2007 was assessed retrospectively. All patients received aspirin (100 mg/d) and another antiplatelet drug such as cilostazol (200 mg/d), ticlopidine (200 mg/d), or clopidogrel (75 mg/d) at least 3 days before CAS. Two antiplatelet drugs were continued for 2 to 3 months after CAS and reduced to one thereafter. Patients were evaluated at 3 and 6 months and at 6-month intervals thereafter with duplex ultrasound (DUS) imaging. Angiography was used for confirmation when stenosis was suspected as >50% with DUS imaging.

RESULTS

We were able to monitor 97 patients for a 12-month period. The overall combined rate of stroke, myocardial infarction, and death was 3.1% at 30 days and 4.1% at 1 year. In-stent recurrent stenosis was documented in 11 patients (11%); in 10 patients (9.7%), this occurred <or=12 months of CAS. In-stent restenosis was significantly reduced in the cilostazol (+) group (0% vs 15.7% [11 of 70], P = .03). Patient characteristics were similar between the cilostazol (+) and cilostazol (-) groups.

CONCLUSIONS

Although this study was retrospective and nonrandomized, the results suggest that cilostazol administration improves long-term patency after CAS due to its inhibitory effect on smooth muscle cell growth.

Efficacy of cilostazol in reducing restenosis in patients undergoing contemporary stent based PCI: a meta-analysis of randomised controlled trials

AIMS

Cilostazol has been associated with reduction in restenosis in patients undergoing coronary and peripheral arterial angioplasty. Our objective was to evaluate the impact of cilostazol on restenosis in patients undergoing contemporary PCI with bare metal (BMS) or drug eluting stents (DES) and treated with aspirin and thienopyridine.

METHODS AND RESULTS

Ten randomised trials (n=2,809 patients) comparing triple antiplatelet therapy (aspirin, thienopyridine and cilostazol) with standard dual antiplatelet therapy were included. Summary risk ratios for restenosis, late loss, target lesion revascularisation (TLR) and target vessel revascularisation (TVR) were calculated using fixed-effects models. Cilostazol was associated with a significant reduction in late loss in BMS (mean difference 0.24 mm, 95% CI 0.15-0.33, p<0.001) and DES groups (mean difference 0.12 mm, 95% CI 0.07-0.18, p<0.001). Cilostazol therapy was associated with a significant reduction in angiographic restenosis (Odds ratio [OR] 0.52, 95% CI 0.41- 0.66, p<0.001) with consistent benefits in patients treated with BMS (OR 0.49, 95% CI 0.35-0.70, p<0.001) or DES (OR 0.54, 95% CI 0.38-0.76, p=0.001). Addition of cilostazol to dual antiplatelet therapy was associated with a significant reduction in TLR (OR 0.38, 95% CI 0.25-0.58, p<0.001), with no difference in subacute stent thrombosis (OR 1.91, 95% CI 0.33-11.08, p=0.47), or major bleeding (OR 0.87, 95% CI 0.44-1.74, P=0.69) but with an increased risk of skin rash (OR 3.67, 95% CI 1.86-7.24, p<0.001).

CONCLUSIONS

Cilostazol in addition to dual antiplatelet therapy is associated with a reduction in angiographic restenosis in patients undergoing stent based PCI. This inexpensive drug may be particularly beneficial in patients who are at high risk of restenosis and it should undergo further evaluation in large, definitive randomised controlled trials.

The primary and secondary prevention of coronary artery disease: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

The following chapter devoted to antithrombotic therapy for chronic coronary artery disease (CAD) is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do or do not outweigh risks, burden, and costs. Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading see the "Grades of Recommendation" chapter by Guyatt et al in this supplement, CHEST 2008; 133[suppl]:123S-131S). Among the key recommendations in this chapter are the following: for patients with non-ST-segment elevation (NSTE)-acute coronary syndrome (ACS) we recommend daily oral aspirin (75-100 mg) [Grade 1A]. For patients with an aspirin allergy, we recommend clopidogrel, 75 mg/d (Grade 1A). For patients who have received clopidogrel and are scheduled for coronary bypass surgery, we suggest discontinuing clopidogrel for 5 days prior to the scheduled surgery (Grade 2A). For patients after myocardial infarction, after ACS, and those with stable CAD and patients after percutaneous coronary intervention (PCI), we recommend daily aspirin (75-100 mg) as indefinite therapy (Grade 1A). We recommend clopidogrel in combination with aspirin for patients experiencing ST-segment elevation (STE) and NSTE-ACS (Grade 1A). For patients with contraindications to aspirin, we recommend clopidogrel as monotherapy (Grade 1A). For long-term treatment after PCI in patients who receive antithrombotic agents such as clopidogrel or warfarin, we recommend aspirin (75 to 100 mg/d) [Grade 1B]. For patients who undergo bare metal stent placement, we recommend the combination of aspirin and clopidogrel for at least 4 weeks (Grade 1A). We recommend that patients receiving drug-eluting stents (DES) receive aspirin (325 mg/d for 3 months followed by 75-100 mg/d) and clopidogrel 75 mg/d for a minimum of 12 months (Grade 2B). For primary prevention in patients with moderate risk for a coronary event, we recommend aspirin, 75-100 mg/d, over either no antithrombotic therapy or vitamin K antagonist (Grade 1A).

Systematic review and meta-analysis of randomized clinical trials appraising the impact of cilostazol after percutaneous coronary intervention

BACKGROUND

Drug-eluting stents reduce the risk of restenosis after percutaneous coronary intervention (PCI) but may pose a risk of thrombosis. Cilostazol, an oral antiplatelet agent with pleiotropic effects including inhibition of neointimal hyperplasia, could hold the promise of preventing both restenosis and thrombosis. We systematically reviewed randomized clinical trials (RCTs) on the angiographic and clinical impact of cilostazol after PCI.

METHODS

We searched RCT in BioMedCentral, CENTRAL, clinicaltrials.gov, EMBASE, and PubMed (November 2007). Coprimary end points were binary angiographic restenosis and repeat revascularization, abstracted and pooled by means of random-effect relative risks (RRs). Small study/publication bias was appraised with multiple methods.

RESULTS

A total of 23 RCTs were included (5428 patients), with median follow-up of 6 months. Pooled analysis showed that cilostazol was associated with statistically significant reductions in binary angiographic restenosis (RR = 0.60 [0.49-0.73], P < .001) and repeat revascularization (RR = 0.69 [0.55-0.86], P = .001). Cilostazol appeared also safe, with no significant increase in the risk of stent thrombosis (RR = 1.35 [0.71-2.57], P = .36) or bleeding (RR = 0.71 [0.43-1.16], P = .17). However, small study bias was evident for both binary restenosis (P < .001) and repeat revascularization (P < .001), suggesting that at least part of the apparent benefits of cilostazol could be due to this type of confounding effect.

CONCLUSIONS

Cilostazol appears effective and safe in reducing the risk of restenosis and repeat revascularization after PCI, but available evidence is limited by small study effects. Awaiting larger RCTs, this inexpensive treatment can be envisaged in selected patients in which drug-eluting stents are contraindicated or when there is a need for neointimal hyperplasia inhibition.

The cardioprotective effect of a statin and cilostazol combination: relationship to Akt and endothelial nitric oxide synthase activation

BACKGROUND

Atorvastatin (ATV) protects against ischemia-reperfusion by upregulating Akt and subsequently, endothelial nitric oxide synthase (eNOS) phosphorylation at Ser-1177. However, when given orally, high doses of ATV (10 mg/kg/d) are needed to achieve maximal protective effect in the rat. Protein kinase A (PKA) also phosphorylates eNOS at Ser-1177. As PKA activity depends on cAMP, cilostazol (CIL), a phosphodiesterase type III inhibitor, may stimulate NO production by activating PKA.

HYPOTHESIS

CIL and ATV may have synergistic effects on eNOS phosphorylation and myocardial infarct size (IS) reduction.

METHODS

Sprague-Dawley rats received 3-day oral pretreatment with: (1) water; (2) low dose ATV (2 mg/kg/d); (3) CIL (20 mg/kg/d): (4) ATV+CIL. Rats underwent 30 min coronary artery occlusion and 4 h reperfusion, or hearts explanted for immunoblotting without being subjected to ischemia. Area at risk (AR) was assessed by blue dye and IS by triphenyl-tetrazolium-chloride.

RESULTS

Body weight and the size of AR were comparable among groups. There were no significant differences among groups in mean blood pressure and heart rate. CIL, but not ATV, reduced IS. IS in the ATV+CIL group was significantly smaller than the other three groups (P < 0.001 for each comparison). ATV, CIL and their combination did not affect total eNOS expression. ATV at 2 mg/kg/d did not affect Ser-1177 P-eNOS levels, whereas CIL increased it (258 +/- 15%). The level of myocardial P-eNOS levels was highest in the ATV+CIL group (406 +/- 7%).

CONCLUSIONS

ATV and CIL have synergistic effect on eNOS phosphorylation and IS reduction. By increased activation of eNOS, CIL may augment the pleiotropic effects of statins.

The vascular effects of cilostazol

Cilostazol is a phosphodiesterase III inhibitor with pharmacological effects that include vasodilation, inhibition of platelet activation and aggregation, inhibition of thrombosis, increased blood flow to the limbs, improvement in serum lipids with lowering of triglycerides and elevation of high density lipoprotein cholesterol, and inhibition of vascular smooth muscle cell growth. Cilostazol has been shown in multiple randomized clinical trials to result in decreased claudication and improved ability to walk in patients with peripheral arterial disease. In addition, cilostazol has been shown in multiple randomized clinical trials to decrease restenosis in the setting of coronary stent implantation. The purpose of the present paper was to review the vascular effects of cilostazol and to present results of the major clinical trials of the use of cilostazol in peripheral arterial disease and percutaneous coronary intervention with stent implantation.

Pharmacologic approaches to restenosis prevention

Despite significant advances in technology and technique, coronary restenosis remains the primary limitation of percutaneous transluminal coronary angioplasty (PTCA). Among patients undergoing PTCA, between 20% and 50% of patients who do not receive a stent and 10%-30% of those who do receive a stent develop restenosis within 6 months of the procedure. Drug-eluting stents, which release high local concentrations of antiproliferative or immunosuppressive agents directly into the vessel wall at the site of the lesion, have dramatically reduced the incidence of restenosis in patients undergoing PTCA. However, even with drug-eluting stents, a significant percentage of higher-risk patients develop in-stent restenosis. These data suggest that a role remains for effective, well-tolerated systemic pharmacologic therapies to further reduce the rate of restenosis. To date, the majority of systemic agents tested for restenosis prevention have failed to show significant benefit. Only 2 agents, probucol and cilostazol, have consistently demonstrated efficacy in preventing restenosis. In addition, the investigational agent AGI-1067 has demonstrated promising efficacy in early clinical trials. Together with drug-eluting stents, these therapies may for the first time reduce the rate of restenosis to near zero, even in high-risk patients, such as individuals with diabetes mellitus.

Characterization of Human Cytochrome P450 Enzymes Involved in the Metabolism of Cilostazol

Cilostazol (OPC-13013; 6-[4-(1-cyclohexl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone) is widely used as an antiplatelet vasodilator agent. In vitro, the hydroxylation of the quinone moiety of cilostazol to OPC-13326 [6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-4-hydroxy-2(1H)-quinolinone], is the predominant route, and the hydroxylation of the hexane moiety to OPC-13217 is the second most predominant route. This study was carried out to identify and kinetically characterize the human cytochrome P450 (P450) isozymes responsible for the formation of the two major metabolites of cilostazol, namely, OPC-13326 and OPC-13217 [3,4-dihydro-6-[4-[1-(cis-4-hydroxycyclohexyl)-1H-tetrazol-5-yl)butoxy]-2(1H)-quinolinone)]. In in vitro studies using 14 recombinant human P450 isozymes, CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP2J2, CYP3A4, CYP3A5, and CYP4A11, cilostazol was metabolized to OPC-13326 mainly by CYP3A4 (K(m) = 5.26 muM, intrinsic clearance (CL(int)) = 0.34 microl/pmol P450/min), CYP1B1 (K(m) = 11.2 microM, CL(int) = 0.03 microl/pmol P450/min), and CYP3A5 (K(m) = 2.89 microM, CL(int) = 0.05 microl/pmol P450/min) and to OPC-13217 mainly by CYP3A5 (K(m) = 1.60 microM, CL(int) = 0.57 microl/pmol P450/min), CYP2C19 (K(m) = 5.95 microM, CL(int) = 0.16 microl/pmol P450/min), CYP3A4 (K(m) = 5.35 microM, CL(int) = 0.10 microl/pmol P450/min), and CYP2C8 (K(m) = 33.8 microM, CL(int) = 0.009 microl/pmol P450/min). The present study showed that the two major metabolites of cilostazol in vitro, namely, OPC-13326 and OPC-13217, are mainly catalyzed by CYP3A4 and CYP3A5, respectively.

Clinical aspects of platelet inhibitors and thrombus formation

The platelet, once thought to be solely involved in clot formation, is now known to be a key mediator in various others processes such as inflammation, thrombosis, and atherosclerosis. Supported by the wealth of evidence from clinical trials demonstrating their benefits in patient outcomes, antiplatelet agents have become paramount in the prevention and management of various diseases involving the cardiovascular, cerebrovascular, and peripheral arterial systems. Despite being among the most widely used and studied classes of medical therapies, new discoveries regarding important clinical aspects and properties of these agents continue to be made. As our understanding of platelet biology expands, more effective and safer novel therapies continue to be developed. The use of more refined agents in conjunction with a better understanding of their effects will further the ability to provide more optimized care on an individual basis.

Reevaluating the role of phosphodiesterase inhibitors in the treatment of cardiovascular disease

First developed for clinical use in the late 1980s, the phosphodiesterase inhibitors were found to increase the levels of the ubiquitous second messenger cyclic adenosine monophosphate and could effect changes in vascular tone, cardiac function, and other cellular events. After several early studies using high doses of phosphodiesterase inhibitors in patients with severe heart failure suggested adverse consequences, they fell out of favor. However, recent investigations of phosphodiesterase inhibitors in patients with intermittent claudication have demonstrated profound benefits. Furthermore, these agents have proven useful in prevention of cerebral infarction and coronary restenosis, and their use in the treatment of heart failure is being reevaluated. The reemergence of phosphodiesterase inhibitors can be attributed to a better understanding of dosing and drug-specific pharmacology, the use of concomitant medications, and a recognition of unique ancillary properties; however, their use still requires caution.

Cilostazol reduces target lesion revascularization after percutaneous transluminal angioplasty in the femoropopliteal artery

BACKGROUND

Although percutaneous transluminal angioplasty (PTA) is being widely used for the treatment of stenosis of peripheral arteries, the high in-stent restenosis rate (50-60%) in the femoropopliteal artery still remains an unsolved issue. Cilostazol is a unique antiplatelet drug that has vasodilatory effects and inhibits smooth muscle cell proliferation.

METHODS AND RESULTS

A total of 141 consecutive patients scheduled for PTA in the femoropopliteal artery between September 1999 and April 2004 were retrospectively analyzed for the use of cilostazol. Target lesion revascularization (TLR) was defined as repeated PTA in patients who had a recurrence of symptoms with diameter stenosis >50% by angiography. Patient and lesion characteristics were similar between the cilostazol (+) and cilostazol (-) groups. Use of other medications was similar between the groups, except for ticlopidine, which was more frequently used in the cilostazol (-) than in the cilostazol (+) group (15% vs 61%, p<0.01). TLR was significantly reduced in the cilostazol (+) group (12% [8/68] vs 32% [23/73], p<0.01).

CONCLUSIONS

Although this study was retrospective and nonrandomized, the results suggest that cilostazol reduces TLR after PTA in the femoropopliteal artery.

Role of adjunct pharmacologic therapy in the era of drug-eluting stents

The success of percutaneous coronary intervention (PCI) has historically been limited by a relatively high rate of restenosis, a response of the coronary artery to trauma induced during PCI. Bare-metal stents, by providing a supportive intravascular scaffolding, have significantly reduced the incidence of restenosis compared with traditional balloon PCI. However, significant loss of lumen within the bare-metal device (in-stent restenosis) occurs in 10-30% of patients within 6 months of the procedure. The recent introduction of drug-eluting stents, permitting local delivery of high concentrations of immunosuppressive or anti-proliferative agents, promises to prevent the processes underlying restenosis. Although these devices have been successful in providing an incremental reduction in rates of restenosis, they are expensive. To date, clinical trials of pharmacologic treatment have failed to demonstrate a clinically significant impact on restenosis. Recently, results of the Cilostazol for Restenosis (CREST) trial, a randomized, double-blind study, show that cilostazol reduces the risk of restenosis in patients who receive bare-metal stents, including high-risk patients. Effective adjunct pharmacologic therapy to prevent in-stent restenosis, therefore, remains desirable, particularly in patients receiving bare-metal stents, and potentially in patients receiving drug-eluting stents who are at high risk for restenosis (i.e., those with diabetes, long lesions, and small vessels).

Pharmacological treatment for prevention of restenosis

Coronary artery disease (CAD) is the leading cause of mortality and morbidity among adults in the Western world. Coronary artery bypass grafting and percutaneous coronary interventions (PCI) have gained widespread acceptance for the treatment of symptomatic CAD. There has been an explosive growth worldwide in the utilisation of PCI, such as balloon angioplasty and stenting, which now accounts for over 50% of coronary revascularisation. Despite the popularity of PCI, the problem of recurrent narrowing of the dilated artery (restenosis) continues to vex investigators. In recent years, significant advances have occurred in the understanding of restenosis. Two processes seem to contribute to restenosis: remodelling (vessel size changes) and intimal hyperplasia (vascular smooth muscle cell [VSMC] proliferation and extracellular matrix [ECM] deposition). Despite considerable efforts, pharmacological approaches to decrease restenosis have been largely unsuccessful and the only currently applied modality to reduce the restenosis rate is stenting. However, stenting only prevents remodelling and does not inhibit intimal hyperplasia. Several potential targets for inhibiting restenosis are currently under investigation including platelet activation, the coagulation cascade, VSMC proliferation and migration, and ECM synthesis. In addition, new approaches for local drug therapy, such as drug eluting stents, are currently being evaluated in preclinical and clinical studies. In this article, we critically review the current status of drugs that are being evaluated for restenosis at various stages of development (in vitro, preclinical animal models and human trials).

Balloon angioplasty plus cilostazol administration versus primary stenting of small coronary artery disease: Final results of COMPASS

Efficacy of primary stenting in small coronary artery disease is still controversial. Cilostazol has been reported to control restenosis after balloon angioplasty (BA). The aim was to compare primary stenting with BA plus cilostazol administration in small coronary artery disease. Of 106 lesions located in small coronary artery (reference < 3.0 mm), 50 lesions were randomly assigned to the stenting and 56 lesions to the BA-cilostazol group. Multilink stent was implanted in the stenting group. In the BA-cilostazol group, cilostazol (200 mg/day) without aspirin was administered for 6 months after BA. Ticlopidine was given for 1 month when bailout stent was implanted. Serial quantitative angiography was performed at the procedure and 6 months. The primary endpoint was 6-month angiographic restenosis. Clinical event rates at 1 year were also assessed. Baseline characteristics were similar. All procedures were successful. Bailout stenting was performed in three lesions in the BA-cilostazol group. No side effects of cilostazol were observed. Postprocedural lumen diameter was significantly larger (2.69 vs. 2.03 mm; P < 0.0001) in the stenting group. However, the follow-up lumen diameter was not different (1.76 vs. 1.85 mm, stenting vs. BA-cilostazol). Although the difference was not statistically significant, restenosis rate was lower in the BA-cilostazol group (13.2% vs. 24.5%; P = 0.11). Subacute thrombosis occurred in one patient and target revascularization rate was higher in the stenting group (22.0% vs. 10.7%; P = 0.10). BA plus cilostazol administration seems to be a favorable strategy for small coronary artery disease.

Debulking and stenting versus debulking only of coronary artery disease in patients treated with cilostazol (final results of ESPRIT)

Stenting inhibits vascular constrictive remodeling after directional coronary atherectomy (DCA). Cilostazol has been reported to control neointimal proliferation after stenting. This study's aim was to examine the effect of debulking and stenting with antirestenotic medication on restenosis. After optimal DCA, 117 lesions were randomly assigned to either the DCA with stent (DCA-stent) (58 lesions) group or the DCA only (59 lesions) group. Multilink stents were implanted in the DCA-stent group. Cilostazol (200 mg/day) without aspirin was administered to both groups for 6 months. Ticlopidine (200 mg/day) was given to the DCA-stent group for 1 month. Serial quantitative angiography and intravascular ultrasound (IVUS) were performed at the time of the procedure and at 6-month follow-up. The primary end point was 6-month angiographic restenosis. Clinical event rates at 1 year were also assessed. Baseline characteristics were similar. All procedures were successful. No adverse effects to cilostazol were observed. Postprocedural lumen diameter was significantly larger (3.27 vs 2.92 mm; p <0.0001) in the DCA-stent group. However, the follow-up lumen diameter was not significantly different (2.53 vs 2.41 mm, DCA-stent vs DCA). IVUS revealed that intimal proliferation was significantly larger in the DCA-stent group (4.2 vs 1.5 mm(2); p <0.0001), which accounted for the similar follow-up lumen area (6.5 vs 7.1 mm(2)). The restenosis rate was low in both groups (5.4% vs 8.9%), and the difference was not significant. Clinical event rates at 1 year were also not significantly different. These results suggest that optimal lesion debulking by DCA does not always need adjunctive stenting if cilostazol is administered.

Potential emerging therapeutic strategies to prevent restenosis in the peripheral vasculature

Despite the availability of antiplatelet and antithrombotic therapies, recent advances in catheter and stent technology and improved operator skill, restenosis remains the most frequent problem associated with percutaneous and surgical revascularization interventions for both coronary and peripheral arterial disease. Prevention of restenosis in the coronary vasculature has been demonstrated with cilostazol, trapidil, probucol, tranilast, nitric oxide donors, and clopidogrel. Given the similarities in revascularization procedures and in the pathophysiology of restenosis, it is possible that these results may be extrapolated to the setting of restenosis in the peripheral vasculature, making trials with these agents imperative. Several new agents have shown promising preliminary results for the prevention of restenosis in the peripheral vasculature, including cilostazol, low-molecular-weight heparins, and elastase. Several nonpharmacologic treatment modalities are also under study to prevent peripheral and coronary restenosis and have shown favorable initial results. These include endovascular radiation brachytherapy, arterial gene therapy, photoangioplasty, and several novel treatment delivery systems.

The pharmacology of cilostazol

Cilostazol (6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone; OPC-13013) is a 2-oxo-quinoline derivative with antithrombotic, vasodilator, antimitogenic and cardiotonic properties. The compound is a potent inhibitor of phosphodiesterase (PDE) 3A, the isoform of PDE 3 in the cardiovascular system (IC50: 0.2 microM). In addition, there is inhibition of adenosine uptake, eventually resulting in changes in cAMP levels, dependent on the type of adenosine receptors (A1 or A2). Cilostazol inhibits platelet aggregation and has considerable antithrombotic effects in vivo. The compound relaxes vascular smooth muscle and inhibits mitogenesis and migration of vascular smooth muscle cells. In the heart, cilostazol causes positive inotropic and chronotropic effects. Most, if not all, of these actions are cAMP-mediated, including the modification of cAMP-controlled gene expression. Cilostazol decreases levels of serum triglycerides and causes some increase in HDL-cholesterol levels. The compound has a number of additional effects which might contribute to its overall clinical efficacy. Cilostazol undergoes intensive and finally complete hepatic metabolism via the cytochrome P450 systems. This might result in some drug interaction, i.e. with erythromycin and omeprazole. The half-life is approximately 10 h, resulting in about 2-fold accumulation of the drug during repeated administration.

Endovascular and surgical revascularization for patients with intermittent claudication

Intermittent claudication (IC), the most common symptom of peripheral arterial disease (PAD), most often results from flow-reducing lesions in the arteries of the lower extremity that cause exercise-induced muscle ischemia. Intermittent claudication has a significant impact on quality of life and calls attention to PAD, which is secondary to systemic atherosclerosis and a major marker for cardiovascular morbidity and mortality. Most IC patients improve with a regimen that includes aggressive risk-factor modification, exercise, platelet inhibition, and pharmacotherapy to improve walking distance. Selected patients may require endovascular or surgical intervention if it can be offered with low risk. Endovascular procedures, most often percutaneous balloon angioplasty with or without stenting, are recommended for short-segment stenotic lesions in the aortoiliac and infrainguinal arterial segments. Combined platelet inhibition and endoluminal radiation are under study and may be useful to improve long-term outcome with these procedures. Percutaneous hemostatic puncture closure devices can also be used to reduce bleeding complications and allow more aggressive and immediate antithrombotic therapy, further improving results. Operative revascularization is recommended for patients with long-segment and multisegment disease, especially if obstruction is present. Aortofemoral reconstruction is associated with a low operative mortality and an 80% to 85% 5-year patency rate. Iliac reconstruction is recommended for isolated unilateral iliac arterial disease. Infrainguinal arterial reconstruction is associated with a 60% to 80% 5-year patency rate, with better outcomes noted for autogenous conduits than for prosthetic devices. Mechanical modification and pharmacotherapy with platelet inhibitors and anticoagulants improve long-term patency.

Effect of cilostazol on restenosis after coronary angioplasty and stenting in comparison to conventional coronary artery stenting with ticlopidine

BACKGROUND

The role of antiplatelet therapy with ticlopidine plus aspirin in the prevention of subacute thrombosis after coronary artery stenting has been established. However, restenosis remains a major limitation in coronary artery stenting.

METHODS

To compare the effect of cilostazol on restenosis after coronary angioplasty and stenting with that of ticlopidine after coronary artery stenting, 213 patients with 230 lesions who underwent successful coronary interventions were evaluated. Optimal results (residual stenosis less than 30%) were obtained by balloon angioplasty in 112 lesions, 64 lesions were treated with aspirin 81 mg/day (balloon-aspirin group) and 48 lesions with cilostazol 200 mg/day and aspirin 81 mg/day (balloon-cilostazol group). Stent implantation was performed in the remaining 118 lesions; 55 lesions were treated with ticlopidine 200 mg/day and aspirin 243 mg/day (stent-ticlopidine group) and 63 lesions with cilostazol 200 mg/day and aspirin 81 mg/day (stent-cilostazol group). Concomitant medications were continued for 4 to 6 months of follow-up.

RESULTS

No adverse events including acute occlusion and subacute thrombosis occurred in any groups. Although immediate gain and minimal lumen diameter immediately after angioplasty were significantly larger in stent groups than those in balloon groups, net gain at follow-up was significantly larger in cilostazol groups (1.54+/-0.83 mm in balloon-cilostazol group and 1.65+/-0.78 mm in stent-cilostazol group) than other groups (1.02+/-0.81 mm in balloon-aspirin group and 1.21+/-0.70 in stent-ticlopidine group) as a result of significantly lower late loss and loss index in cilostazol groups. The restenosis rate was significantly lower in cilostazol groups (12.5% in balloon-cilostazol group and 14.3% in stent-cilostazol group) than other groups (43.8% in balloon-aspirin group and 32.7% in stent-ticlopidine group). The rate of recurrent angina was significantly lower in cilostazol groups (4.3% in balloon-cilostazol group and 1.9% in stent-cilostazol group) than in other groups (17.5% in balloon-aspirin group and 14.0% in stent-ticlopidine groups).

CONCLUSIONS

Both optimal balloon angioplasty with cilostazol and coronary artery stenting with cilostazol have a potential to reduce restenosis compared with optimal balloon angioplasty with aspirin or conventional coronary artery stenting with ticlopidine plus aspirin.

Decrease in carotid intima media thickness after 1 year of cilostazol treatment in patients with type 2 diabetes mellitus

A multicenter exploratory study at three university hospitals was performed to evaluate the effect of oral cilostazol on intima media thickness (IMT) in diabetic patients. A total of 141 patients was recruited in this study and randomized into a cilostazol group and a placebo (control) group. One hundred and twenty patients completed the study (i.e. 60 on cilostazol and 60 on placebo). Biochemical profiles and the IMT of the common carotid artery (CCA) determined by high-resolution B-mode ultrasonography were measured at 0, 6, and 12 months after the oral administration of 100--200 mg of cilostazol or placebo (i.e. two or four times daily for 12 months). Clinical and biochemical characteristics, the treatment modality, and microvascular diabetic complications after randomization were not significantly different between the two groups after the study. In the cilostazol treatment group, left CCA average IMT significantly decreased from 0.94+/-0.03 to 0.91+/-0.02 mm at 6 months (P<0.05), and thereafter increased to 0.92+/-0.01 mm (P>0.05) at 12 months, whereas in the control group, it increased from 0.92+/-0.03 to 0.93+/-0.01 mm at 6 months (P>0.05), and to 0.94+/-0.01 mm at 12 months (P>0.05). As for the right CCA average IMT, it decreased from 0.83+/-0.03 to 0.82+/-0.01 mm at 6 months (P<0.05), and to 0.81+/-0.01 mm at 12 months (P<0.05) in the cilostazol group, whereas it increased from 0.87+/-0.03 to 0.89+/-0.01 mm at 6 months (P<0.05), and to 0.90+/-0.01 mm at 12 months (P<0.05) in the control group (P<0.05). After correction for risk factors such as blood pressure, smoking, and lipid profiles, there were significant changes in left and right CCA average IMT for both groups (P<0.05). Left and right CCA average IMT was significantly different between the two groups (P<0.05). After making statistical corrections for blood pressure, smoking, and lipid profiles, the differences between these two groups remained significant (P<0.05). Meanwhile, there were no differences between the groups in the change of risk factors such as BMI, blood pressure, blood sugar, HbA(1c), and lipid profiles. Generally, cilostazol was well tolerated and the most common side effect in the cilostazol group was headache (12/60), mostly early in the treatment regimen. The results suggest that oral cilostazol may be helpful in the treatment of atherosclerosis in type 2 diabetic patients, although conventional cardiovascular risk factors remained unmodified.

Cilostazol: treatment of intermittent claudication

OBJECTIVE

To review the pharmacology and clinical utility of cilostazol, an antiplatelet and vasodilator agent approved for the management of intermittent claudication.

DATA SOURCES

Primary literature on cilostazol was identified from a comprehensive MEDLINE literature search (1980-February 2000). Selected meeting abstracts and manufacturer literature were also used as source material. Indexing terms included cilostazol, intermittent claudication, platelet inhibitors, and restenosis.

STUDY SELECTION

Human clinical, pharmacokinetic and randomized comparative trials performed in the US and Asia were reviewed. Selected in vitro, ex vivo, and animal studies were evaluated when human data were not available.

DATA SYNTHESIS

Intermittent claudication, defined as reproducible discomfort of a muscle group induced by exercise and relieved by rest, is the most common clinical manifestation of peripheral arterial disease (PAD). Cilostazol, a specific inhibitor of cyclic adenosine monophosphate phosphodiesterase in platelets and vascular smooth-muscle cells, is a potent antiplatelet agent and vasodilator that reduces vascular proliferation and has lipid-lowering effects in vivo. Recent multicenter, randomized, placebo-controlled trials have led to approval of cilostazol by the Food and Drug Administration for relief of intermittent claudication in patients with stable PAD. Cilostazol doubled walking distances and improved quality of life compared with placebo in these studies. One trial found that cilostazol was more effective than pentoxifylline, the only alternative pharmacologic therapy for claudication. Although frequent (approximately 50%) minor adverse effects, including headache, diarrhea, and palpitations, may occur in clinical practice, cilostazol has not been associated with major adverse events or increased mortality. Small, nonblind studies suggest that cilostazol may prove useful in preventing thrombosis and restenosis following percutaneous coronary interventions, although these remain unlabeled uses.

CONCLUSIONS

The unique combination of antiplatelet, vasodilatory, and antiproliferative effects of cilostazol appear to make it an attractive agent for use in patients with PAD. Clinical trials demonstrating a significant improvement in walking distances with cilostazol therapy suggest that it will be an important tool in improving symptoms and quality of life in patients with intermittent claudication.

Effects of cilostazol on late lumen loss and repeat revascularization after Palmaz-Schatz coronary stent implantation

BACKGROUND

Cilostazol is an antiplatelet agent that increases the intracellular concentration of cyclic adenosine monophosphate by inhibiting phosphodiesterase III; it has been shown to reduce neointimal hyperplasia in animal balloon injury models.

METHODS

One hundred thirty patients who underwent elective stenting (Palmaz-Schatz stent) were randomly assigned to cilostazol treatment 200 mg/d (n = 65) or to ticlopidine treatment 200 mg/d (n = 65). Angiographic follow-up was performed at 6 months, and clinical follow-up was continued up to 1 year.

RESULTS

One sudden death and one myocardial infarction resulting from subacute occlusion were observed in the ticlopidine group. Drug adverse effects were observed in 3 patients in the cilostazol group, as opposed to 6 patients in the ticlopidine group. In the intention-to-treat analysis, 56 patients (61 lesions) in the cilostazol group and 58 patients (58 lesions) in the ticlopidine group were assessed with quantitative coronary angiography. Late loss in the cilostazol group was smaller (0.58+/-0.52 mm vs. 1.09+/-0.65 mm, P<.0001) than in the ticlopidine group. The restenosis rate was lower in the cilostazol group than in the ticlopidine group (16% vs. 33%, P = .044). The target vessel revascularization rate at 1 year was 23% in the cilostazol group and 42% in the ticlopidine group (P =.03).

CONCLUSIONS

The results of this study suggest that cilostazol may be a safe medication that is effective in preventing restenosis after stent implantation.

Nitric oxide and postangioplasty restenosis: pathological correlates and therapeutic potential

Balloon angioplasty revolutionized interventional cardiology as a nonsurgical procedure to clear a diseased artery of atherosclerotic blockage. Despite its procedural reliability, angioplasty's long-term outcome can be compromised by restenosis, the recurrence of arterial blockage in response to balloon-induced vascular trauma. Restenosis constitutes an important unmet medical need whose pathogenesis has yet to be understood fully and remains to be solved therapeutically. The radical biomediator, nitric oxide (NO), is a natural modulator of several processes contributing to postangioplasty restenosis. An arterial NO deficiency has been implicated in the establishment and progression of restenosis. Efforts to address the restenosis problem have included trials evaluating a wide range of NO-based interventions for their potential to inhibit balloon-induced arterial occlusion. All types of NO-based interventions yet investigated benefit at least one aspect of balloon injury to a naive vessel in a laboratory animal without inducing significant side effects. The extent to which this positive, albeit largely descriptive, body of experimental data can be translated into the clinic remains to be determined. Further insight into the pathogenesis of restenosis and the molecular mechanisms by which NO regulates vascular homeostasis would help bridge this gap. At present, NO supplementation represents a unique and potentially powerful approach to help control restenosis, either alone or as a pharmaceutical adjunct to a vascular device.

Suppression of arterial intimal hyperplasia by cilostamide, a cyclic nucleotide phosphodiesterase 3 inhibitor, in a rat balloon double-injury model

The effects of cilostamide, a cyclic nucleotide phosphodiesterase 3 (PDE3) selective inhibitor, on vascular intimal hyperplasia were evaluated using a single-balloon injury model and a double-injury model in which the rat common carotid artery was subjected to a second injury at a site injured 14 days previously. In the double-injury model, the second balloon injury caused more severe intimal hyperplasia (intima/media (IM) ratio, 1.88+/-0.10) than in the single-injury model (1.09+/-0.08). Histopathological study revealed that vascular smooth muscle cells (VSMC) were the predominant cell-type in the affected neointimal area. Oral administration of cilostamide for 2 weeks after the second injury suppressed intimal hyperplasia in the double-injury model (30 mg kg(-1) bid, 83% inhibition in terms of the IM ratio, P<0.05; 100 mg kg(-1) bid, 69% inhibition, P<0.05). Similar effects were also observed in the single-injury model with oral administration of cilostamide for 2 weeks (100 mg kg(-1) bid, 36% inhibition, P<0.01). Cilostamide inhibited DNA synthesis of cultured VSMC stimulated by foetal calf serum or different kinds of growth factors, but did not affect their migration stimulated by platelet-derived growth factor (PDGF)-BB. Cilostamide significantly increased the cyclic AMP concentration of VSMC dose-dependently. These results indicate that cilostamide suppresses intimal hyperplasia both in the single- and double-injury models of rat, presumably by inhibiting proliferation rather than migration of VSMC. It is suggested that PDE3 inhibitors might find application in preventing intimal hyperplasia following angioplasty such as percutaneous transluminal coronary angioplasty (PTCA) or stent.

Impact of cilostazol on clinical and angiographic outcome after primary stenting for acute myocardial infarction

Cilostazol, an antiplatelet drug that also may inhibit smooth muscle proliferation, was given together with aspirin after primary stenting to treat patients with acute myocardial infarction. In a randomized controlled trials of 50 patients, clinical and angiographic outcome at 6 months was significantly improved with cilostazol, depicting a significantly smaller late loss and/or loss index.

Final results of the STent versus directional coronary Atherectomy Randomized Trial (START)

OBJECTIVES

This study was designed to compare primary stenting with optimal directional coronary atherectomy (DCA).

BACKGROUND

No previous prospective randomized trial comparing stenting and DCA has been performed.

METHODS

One hundred and twenty-two lesions suitable for both Palmaz-Schatz stenting and DCA were randomly assigned to stent (62 lesions) or DCA (60 lesions) arm. Single or multiple stents were implanted with high-pressure dilation in the stent arm. Aggressive debulking using intravascular ultrasound (IVUS) was performed in the DCA arm. Serial quantitative angiography and IVUS were performed preprocedure, postprocedure and at six months. The primary end point was restenosis, defined as > or =50% diameter stenosis at six months. Clinical event rates at one year were also assessed.

RESULTS

Baseline characteristics were similar. Procedural success was achieved in all lesions. Although the postprocedural lumen diameter was similar (2.79 vs. 2.90 mm, stent vs. DCA), the follow-up lumen diameter was significantly smaller (1.89 vs. 2.18 mm; p = 0.023) in the stent arm. The IVUS revealed that intimal proliferation was significantly larger in the stent arm than in the DCA arm (3.1 vs. 1.1 mm ; p < 0.0001), which accounted for the significantly smaller follow-up lumen area of the stent arm (5.3 vs. 7.0 mm2; p = 0.030). Restenosis was significantly lower (32.8% vs. 15.8%; p = 0.032), and target vessel failure at one year tended to be lower in the DCA arm (33.9% vs. 18.3%; p = 0.056).

CONCLUSIONS

These results suggest that aggressive DCA may provide superior angiographic and clinical outcomes to primary stenting.

Impact of cilostazol on restenosis after percutaneous coronary balloon angioplasty

BACKGROUND

Restenosis after percutaneous transluminal coronary (balloon) angioplasty (PTCA) remains a major drawback of the procedure. We previously reported that cilostazol, a platelet aggregation inhibitor, inhibited intimal proliferation after directional coronary atherectomy and reduced the restenosis rate in humans. The present study aimed to determine the effect of cilostazol on restenosis after PTCA.

METHODS AND RESULTS

Two hundred eleven patients with 273 lesions who underwent successful PTCA were randomly assigned to the cilostazol (200 mg/d) group or the aspirin (250 mg/d) control group. Administration of cilostazol was initiated immediately after PTCA and continued for 3 months of follow-up. Quantitative coronary angiography was performed before PTCA and after PTCA and at follow-up. Reference diameter, minimal lumen diameter, and percent diameter stenosis (DS) were measured by quantitative coronary angiography. Angiographic restenosis was defined as DS at follow-up >50%. Eligible follow-up angiography was performed in 94 patients with 123 lesions in the cilostazol group and in 99 patients with 129 lesions in the control group. The baseline characteristics and results of PTCA showed no significant difference between the 2 groups. However, minimal lumen diameter at follow-up was significantly larger (1.65+/-0.55 vs 1.37+/-0.58 mm; P<0.0001) and DS was significantly lower (34.1+/-17.8% vs 45.6+/-19. 3%; P<0.0001) in the cilostazol group. Restenosis and target lesion revascularization rates were also significantly lower in the cilostazol group (17.9% vs 39.5%; P<0.001 and 11.4% vs 28.7%; P<0. 001).

CONCLUSIONS

Cilostazol significantly reduces restenosis and target lesion revascularization rates after successful PTCA.

Cilostazol

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