Drug Insight: antithrombotic therapy after percutaneous coronary intervention in patients with an indication for anticoagulation

A novel indication of platonin, a therapeutic immunomodulating medicine, on neuroprotection against ischemic stroke in mice

Thrombosis and stroke are major causes of disability and death worldwide. However, the regular antithrombotic drugs may have unsatisfactory results and side effects. Platonin, a cyanine photosensitizing dye, has been used to treat trauma, ulcers and some acute inflammation. Here, we explored the neuroprotective effects of platonin against middle cerebral artery occlusion (MCAO)-induced ischemic stroke in mice. Platonin(200 μg/kg) substantially reduced cerebral infarct volume, brain edema, neuronal cell death and neurological deficit scores, and improved the MCAO-reduced locomotor activity and rotarod performance. Platonin(5–10 μM) potently inhibited platelet aggregation and c-Jun NH2-terminal kinase (JNK) phosphorylation in collagen-activated platelets. The antiaggregation effect did not affect bleeding time but increased occlusion time in platonin(100 and 200 μg/kg)-treated mice. Platonin(2–10 μM) was potent in diminishing collagen- and Fenton reaction-induced ^∙OH formation. Platonin(5–10 μM) also suppressed the expression of nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, interleukin-1β, and JNK phosphorylation in lipopolysaccharide-stimulated macrophages. MCAO-induced expression of 3-nitrotyrosine and Iba1 was apparently attenuated in platonin(200 μg/kg)-treated mice. In conclusion, platonin exhibited remarkable neuroprotective properties against MCAO-induced ischemia in a mouse model through its antiaggregation, antiinflammatory and antiradical properties. The observed therapeutic efficacy of platonin may consider being a novel medcine against ischemic stroke.

Antithrombotic activity of Vitis labrusca extract on rat platelet aggregation

Vitis labrusca is a grapevine that has antioxidant, neuroprotective, hepatoprotective, and anticarcinogenic activity. However, the antithrombotic effect of Vitis labrusca leaves on platelets is yet to be ascertained. We investigated the inhibitory effect of V. labrusca leaf extract (VLE) on platelet aggregation in vitro and ex vivo. The thromboxane B2 (TXB2) and serotonin concentrations were measured by ELISA. The flavonoids content was measured by ultraperformance liquid chromatography (UPLC). The antithrombotic activity of VLE was evaluated using various agonists in vitro. VLE strongly inhibited adenosine diphosphate (ADP)-induced platelet aggregation. In rats, VLE treatment (100 mg/kg) reduced ADP-stimulated platelet aggregation, without affecting tail bleeding and coagulation time. Moreover, VLE significantly suppressed TXB2 and serotonin secretion. UPLC analysis indicated that VLE contains quercetin, isorhamnetin, and rutin. Our results indicate that VLE possesses antiplatelet activity via the suppression of TXB2 and serotonin, without affecting bleeding. Further, we identified the flavonoids present in VLE. Thus, VLE may be a potential agent for the prevention of cardiovascular diseases.

Chloroform fraction of Euphorbia maculata has antiplatelet activity via suppressing thromboxane B2 formation

Euphorbia maculata (EM) is a traditionally used antidiarrheal, antibacterial, antifungal and antioxidant agent. However, the effects of EM on platelet activity remain to be elucidated. Therefore, the present study investigated the antiplatelet effect of various EM extract fractions on platelet aggregation in rats. The antiplatelet activity of the EM fractions on collagen or adenosine diphosphate (ADP)‑induced platelet aggregation was evaluated in vitro and ex vivo. Thromboxane B2 (TXB2) formation, rat‑tail bleeding time and coagulation time were also measured. Among the fractions, the chloroform fraction of EM (CFEM) significantly inhibited ADP‑induced platelet aggregation in vitro. Furthermore, oral administration of 50 mg/kg CFEM to rats significantly reduced ADP‑induced platelet aggregation without increasing the tail bleeding time or coagulation time. In addition, EM significantly inhibited the level of TXB2 formation in a dose‑dependent manner. These results suggest that CFEM exhibits antiplatelet activity, without causing bleeding, via the suppression of TXB2 formation. CFEM may be a type of food which has the potential for preventing cardiovascular disease.

Extract of Antrodia camphorata exerts neuroprotection against embolic stroke in rats without causing the risk of hemorrhagic incidence

In this study, the neuroprotective effect of an extract of Antrodia camphorata (A. camphorata), a fungus commonly used in Chinese folk medicine for treatment of viral hepatitis and cancer, alone or in combination with aspirin was investigated in a rat embolic stroke model. An ischemic stroke was induced in rats by a selective occlusion of the middle cerebral artery (MCA) with whole blood clots and then orally treated with A. camphorata (0.25 and 0.75 g/kg/day) alone and combined with aspirin (5 mg/kg/day). Sixty days later, the brains were removed, sectioned, and stained with triphenyltetrazolium chloride and analysed by a commercial image processing software program. Brain infarct volume, neurobehavioral score, cerebral blood perfusion, and subarachnoid and intracerebral hemorrhage incidence were perceived. In addition, potential bleeding side effect of the combinative therapy was assessed by measuring hemoglobin (Hb) content during intracerebral hemorrhage and gastric bleeding, prothrombin time (PT), and occlusion time (OT) after oral administration. Posttreatment with high dose A. camphorata significantly reduced infarct volume and improved neurobehavioral score (P < 0.05). Since A. camphorata alone or with aspirin did not alter the Hb level, this treatment is safe and does not cause hemorrhagic incident. Remarkably, the combination of A. camphorata and aspirin did not show a significant effect on the bleeding time, PT and OT increase suggesting that A. camphorata may have the neuroprotective effect without the prolongation of bleeding time or coagulation time. From these observations, we suggest that combinative therapy of A. camphorata and aspirin might offer enhanced neuroprotective efficacies without increasing side effects.

The aging patient with hemophilia

The prospects for many boys born with hemophilia today include a normal life expectancy and minimal to no joint disease. However, despite the availability of safe replacement clotting factor concentrates and effective antiviral treatment, the aging patient with hemophilia today faces many challenges. These include management of their hemophilia as well as the same age-related health issues as experienced in the general population. While increasing, data on the prevalence of comorbidities and their management in the hemophilia population remain limited. This review will focus on issues related to management of hemophilia and complications of cardiovascular, musculoskeletal, hepatic, and renal disease. Available research is summarized and potential approaches to management are discussed.

Long-term safety of drug-eluting stents in patients on warfarin treatment

BACKGROUND

The safety of drug-eluting stents (DES) in patients on long-term warfarin treatment has been questioned due to high risk of bleeding complications during prolonged triple (aspirin, clopidogrel, and warfarin) antithrombotic therapy.

METHODS

We analysed the long-term outcome of 415 consecutive warfarin-treated patients who underwent DES (n = 191) or bare-metal (n = 224) stenting in six hospitals.

RESULTS

The mean duration of triple therapy was longer (4.2 ± 3.1 versus 2.1 ± 1.8 months; P < 0.001) in the DES group. The incidence of major adverse cardiovascular and cerebrovascular events was comparable in the DES and bare-metal groups (39.8% versus 42.4%; P = 0.59) during a median follow-up of 3.5 years. Similarly, major bleeding events occurred equally often in both study groups (14.7% versus 12.9%). Six patients in the DES group and seven patients in the bare-metal group suffered stent thrombosis (3.1% versus 3.1%). In the propensity score analyses of 101 matched pairs, the outcome was similar in the two groups.

CONCLUSION

Selective use of DES with a short triple therapy seems to be safe in patients with warfarin therapy. The prognosis of this fragile patient population is quite poor, and major bleeding events are common irrespective of stent type.

Antithrombotic effects of Danggui, Honghua and potential drug interaction with clopidogrel

AIM OF THE STUDY

The antithrombotic effect of Danggui and Honghua, herbs commonly used in Traditional Chinese medicine to treat the syndrome corresponding to vascular thrombosis, and their potential interactions with clopidogrel were investigated.

MATERIALS AND METHODS

The efficacy of Danggui, Honghua alone or combination with clopidogrel was determined in three experimental models. Bleeding time and hematology parameters were measured to evaluate safety.

RESULTS

Danggui and Honghua exhibited antithrombotic effects against venous thrombosis and pulmonary embolism. Especially in the case of venous thrombosis, the thrombus weight was decreased significantly by Danggui or Honghua when compared with control. Bleeding time and coagulation time tended to be prolonged by Danggui or Honghua, but only prothrombin time (PT) and thrombin time (TT) were augmented significantly. The combinations of Danggui plus clopidogrel and of Honghua plus clopidogrel failed to significantly enhance the antithrombotic effects of clopidogrel alone against arterial thrombosis, venous thrombosis and pulmonary embolism. However, both Danggui and Honghua significantly potentiated the prolongation caused by clopidogrel on the tail bleeding time and PT.

CONCLUSIONS

Danggui and Honghua possess antithrombotic activity and cannot potentiate the antithrombotic effect of clopidogrel. However, they significantly enhance the deleterious effect of clopidogrel on bleeding time, PT and TT.

Safety of the cardiac triple therapy: the experience of the Quebec Heart Institute

BACKGROUND

Contemporary treatment of acute coronary syndrome is based on the combination of acetylsalicylic acid (ASA) and clopidogrel. However, an increasing proportion of patients with cardiovascular disease also have an indication for anticoagulant therapy with warfarin. The combination of ASA, clopidogrel and warfarin, also called the cardiac triple therapy (CTT), is emerging in clinical practice, although little is known about its safety.

OBJECTIVES

To determine the risk of major and minor bleeding associated with the CTT compared with two other regimens using the combination of either ASA and clopidogrel or ASA and warfarin in patients with cardiovascular disease.

METHODS

A retrospective study was performed of all susceptible patients who may have received the CTT on discharge from the Quebec Heart Institute (Sainte-Foy, Quebec) between 2002 and 2005. The charts of patients treated with the CTT, ASA and clopidogrel, or ASA and warfarin were reviewed and patients were interviewed to document any bleeding episodes.

RESULTS

A total of 183 patients were studied. Overall bleeding in the CTT group was 3% compared with 5% in the group receiving ASA and clopidogrel and 16% in the group receiving ASA and warfarin (P=0.03). Patients who experienced bleeding were older, had more hypertension and had been exposed to their drug regimens for a longer duration. There was no significant difference in major bleeding episodes.

CONCLUSIONS

The CCT appears to be relatively safe compared with other regimens. Higher bleeding rates within the ASA-warfarin group emphasize the need to carefully educate and follow patients on combination therapy.

Balancing myocardial ischemic and bleeding risks in patients with non-ST-segment elevation myocardial infarction

Achieving an appropriate balance of anti-ischemic efficacy versus bleeding risk with antiplatelet and anticoagulant agents demands an accurate estimation of risks. Although traditional risk stratification is available to decrease complications, and various methods of stratifying these risks have been proposed and validated, the stratification of bleeding risk is in its infancy. However, no model currently available permits the simultaneous estimation of these risks. Ischemic risk may be determined using 1 of several validated models, followed by the estimation of bleeding risk according to known risk factors. After selecting appropriate pharmacotherapy on the basis of the stratification of these risks, attention must be paid to proper dosing according to individual risk factors and patient, clinical, and technical variables. The aim of this study was to examine risk stratification models for these parameters to determine clinical characteristics common to ischemia and bleeding that can be used to minimize risks. A "bleeding risk subscale" is proposed, with factors extrapolated from current ischemic risk models, to integrate ischemic mortality and bleeding risk in patients with non-ST-segment elevation acute coronary syndromes. In conclusion, a validated tool to simultaneously evaluate ischemic and bleeding risk will help determine the most well-balanced pharmacotherapy for patients with non-ST-segment elevation acute coronary syndromes.

[Drug-eluting stents: implications for surgery patients]

Percutaneous coronary intervention (PCI) has a special role in the treatment of coronary heart disease. The insertion of drug-eluting stents (DES) requires dual anti-platelet therapy for at least 1 year which makes planned and emergency surgery difficult. There is a dilemma between high risk of stent thrombosis and perioperative bleeding. There is no evidence-based, bridging therapy option available perioperatively. This complex of problems should be considered whenever PCI is performed. An interdisciplinary approach is obligatory in these imminent conditions to proceed with either interventional or surgical revascularization. Co-existing malignancies and disorders which must be treated surgically should be excluded before PCI. Furthermore, DES and dual anti-platelet therapy produce unanswered forensic questions. On legal grounds it is not possible to proceed with surgery in cases of medication with anti-platelet therapy. Therefore, it is mandatory to discuss the possible answers to this problem with health care lawyers. The patient must be informed about this complex of problems.

Aspirin and clopidogrel with or without phenprocoumon after drug eluting coronary stent placement in patients on chronic oral anticoagulation

OBJECTIVES

Optimal antithrombotic/anticoagulation therapy in patients on chronic oral anticoagulation (OAC) undergoing drug-eluting stent (DES) implantation is unknown. We investigated the efficacy and safety of two regimens of antithrombotic/anticoagulation therapy in patients who present for DES implantation whilst on OAC.

METHODS

We included a series of 515 patients on OAC who underwent DES implantation between 2002 and 2007. Based on predefined clinical and echocardiographic criteria, 306 patients continued OAC (triple therapy) and 209 patients discontinued OAC (dual therapy) for the time they received antiplatelet therapy with clopidogrel and aspirin [stent-related antithrombotic treatment (SRAT)]. The primary end point was a composite of death, myocardial infarction, stent thrombosis or stroke.

RESULTS

During SRAT the primary endpoint was observed in 13 patients in the group with triple therapy versus 15 patients in the group with dual therapy [Kaplan-Meier estimates 4.2% and 7.2%, odds ratio (OR) = 0.61, 95% confidence interval (CI) 0.29-1.28; P = 0.19]. At 2 years of follow-up, the primary endpoint was observed in 35 patients in the group with triple therapy versus 36 patients in the group with dual therapy (Kaplan-Meier estimates 14.1% and 18.0%, OR = 0.76, 95% CI: 0.48-1.21; P = 0.25). Two-year incidence of major bleeding was 1.4% (n = 4, triple therapy) versus 3.1% (n = 6, dual therapy) (P = 0.34).

CONCLUSIONS

In patients on chronic OAC undergoing DES implantation, clinical and echocardiographic criteria help to define postprocedural antithrombotic/anticoagulation therapy. Based on these criteria, both a double antiplatelet therapy (clopidogrel plus aspirin) and a triple therapy (OAC plus clopidogrel plus aspirin) are associated with favourable safety and efficacy.

Safety of diagnostic coronary angiography during uninterrupted therapeutic warfarin treatment

Long-term warfarin therapy is assumed to increase bleeding and access site complications after coronary angiography and it is often recommended to postpone invasive procedures to reach international normalized ratio (INR) levels <1.8. To assess the safety and feasibility of diagnostic coronary angiography during uninterrupted warfarin therapy, we retrospectively analyzed all consecutive patients (n = 258) on warfarin therapy referred for diagnostic coronary angiography in 2 centers with long experience in uninterrupted warfarin therapy during coronary angiography and in 1 center with a policy of preprocedural warfarin pause. An age- and gender-matched control group (n = 258) with similar disease presentation (unstable or stable symptoms) was collected from each center. Radial access was used in 56% of patients in the warfarin group and in 60% of controls (p = 0.21). There was no difference in access site and bleeding complications (1.9% vs 1.6%) or major adverse cardiovascular and cerebrovascular events (0.4% vs 0.8%) between the warfarin group and their controls. Warfarin was interrupted in 80 patients (31%), and bridging therapy was used in 24 of these patients (30%). INR levels were higher in the uninterrupted warfarin group (2.3 vs 1.9, p <0.001), but the incidence of access site complications was not higher (1.7%) than in patients (n = 80) with a warfarin pause (2.5%) or in patients with pause and bridging therapy (8.3%). Need for blood transfusions (n = 2) occurred only in patients with bridging therapy. Access site complications were more common in the 22 patients with supratherapeutic anticoagulation (INR >3) than in patients with therapeutic periprocedural INR (9.1% vs 1.5%, p <0.05). In conclusion, a simple strategy of performing coronary angiography during uninterrupted therapeutic warfarin anticoagulation is a tempting alternative to bridging therapy and is likely to lead to considerable cost savings.

Affinity manipulation of surface-conjugated RGD peptide to modulate binding of liposomes to activated platelets

Platelet adhesion, activation and fibrinogen-mediated aggregation are primary events in vascular thrombosis and occlusion. An injectable delivery system that can carry thrombolytics selectively to the sites of active platelet aggregation has immense potential in minimally invasive targeted therapy of vascular occlusion. To this end we are studying liposomes surface-modified by fibrinogen-mimetic RGD motifs that can selectively target and bind integrin GPIIb-IIIa on activated platelets. Here we report liposome surface-modification with a conformationally constrained high affinity cyclic RGD motif to modulate the GPIIb-IIIa-binding capability of the liposomes. Such affinity enhancement is important for practical in vivo applications to compete with native fibrinogen towards binding GPIIb-IIIa. The platelet-binding of RGD-modified liposomes was studied by fluorescence and scanning electron microscopy, and flow cytometry, in vitro. Binding of RGD-modified liposomes was also tested in vivo in a rat carotid injury model and analyzed ex vivo by fluorescence microscopy. The results from all experiments show that cyclic RGD-liposomes bind activated platelets significantly higher compared to linear RGD-liposomes. Hence, the results establish the feasibility of modulating the platelet-targeting and binding ability of vascularly targeted liposomes by manipulating the affinity of surface-modifying ligands.