Inhibitory effect of clentiazem (TA-3090) on platelet aggregation--alone and in combination with aspirin or ticlopidine

Proton pump inhibitors are associated with lower gastrointestinal tract bleeding in low-dose aspirin users with ischaemic heart disease

BACKGROUND

Impact of acid suppressants on lower gastrointestinal bleeding remains unclear in low-dose aspirin users; we aimed to investigate this relationship.

METHODS

Retrospective cohort study of low-dose aspirin users who underwent coronary angiography for ischaemic heart disease in our institution between October 2005 and December 2006; patients were evaluated for upper or lower gastrointestinal bleedings within 3 years post-angiography.

RESULTS

538 patients were enrolled (males, 74.4%; mean age 67.4±10.6 years). Risk for upper gastrointestinal bleeding decreased with concomitant use of statins (HR, 0.37; 95% CI, 0.15-0.89), calcium channel blockers (HR, 0.29; 95% CI, 0.10-0.85), and histamine-2 receptor antagonists (HR, 0.26; 95% CI, 0.08-0.89). Concomitant use of proton pump inhibitors tended to decrease risk of upper gastrointestinal bleeding (HR, 0.27; 95% CI, 0.06-1.18). Risk for lower gastrointestinal bleeding increased with both concomitant use of warfarin (HR, 15.68; 95% CI, 4.43-55.53) and proton pump inhibitors (HR, 6.55; 95% CI, 2.01-21.32), but not with histamine-2 receptor antagonists. Hyperuricemia lowered risk for lower gastrointestinal bleeding (HR, 0.12; 95% CI, 0.02-0.88).

CONCLUSIONS

In low-dose aspirin users, concomitant use of proton pump inhibitors increased lower gastrointestinal bleeding risk, independent from effects on upper gastrointestinal bleeding.

Interaction between nonsteroidal anti-inflammatory drug intake and calcium-channel blocker-based antihypertensive treatment in the Syst-Eur trial

OBJECTIVE

To assess the relationship between chronic intake of nonsteroidal anti-inflammatory drugs (NSAID) and outcome, in particular (gastrointestinal) bleeding and to investigate whether the effect of chronic NSAID intake was similar in untreated and treated elderly hypertensives.

METHODS

Eligible patients (> or = 60 years, with systolic blood pressure 160-219 mm Hg and diastolic blood pressure < 95 mm Hg) were randomised to active treatment or placebo. Active treatment consisted of nitrendipine, with the possible addition of enalapril, hydrochlorothiazide, or both, titrated or combined to reduce the sitting systolic blood pressure by at least 20 mm Hg to below 150 mm Hg. Patients never taking NSAIDs (n = 2882) were compared with patients on chronic NSAID intake (n = 861), defined as reporting NSAID intake on at least 50% of the patient forms.

RESULTS

There was a tendency towards lower mortality (relative hazard rate (95% confidence interval (CI), 0.77 (0.56-1.06)) and higher incidence of bleeding (1.13 (0.63-2.05) with chronic NSAID intake. Although there was no significant interaction between calcium-channel blocker (CCB)-based treatment and chronic NSAID intake for any of the end points, chronic NSAID intake tended to be associated with a lower incidence of bleeding on active treatment as compared to placebo (P-value of the interaction term = 0.07).

CONCLUSION

The effect of chronic NSAID intake on outcome was similar in patients on active treatment based on a dihydropyridine CCB or on placebo. However, chronic NSAID intake might have a less deleterious effect on bleeding on active treatment as compared to placebo.

Antiplatelet mechanisms of TA-993 and its metabolite MB3 in ADP-induced platelet aggregation

We investigated the antiplatelet mechanisms of TA-993 [(-)-cis-3-acetoxy-5-(2-(dimethylamino)ethyl)-2, 3-dihydro-8-methyl-2-(4-methylphenyl)-1,5-benzothiazepin-4(5H)-one maleate] and its metabolite MB3 (deacetyl and N-monomethyl TA-993) in human platelets stimulated by ADP in vitro. TA-993 and MB3 concentration-dependently inhibited fibrinogen binding to the ADP-stimulated platelets as well as inhibiting platelet aggregation. The antiplatelet effect of MB3 was about 300 times more potent than those of TA-993 and a glycoprotein IIb/IIIa receptor antagonist, Arg-Gly-Asp-Ser (RGDS). Aggregation of ADP-treated fixed platelets caused by the addition of fibrinogen was inhibited by RGDS but not by TA-993 and MB3. TA-993 and MB3 inhibited ADP-induced polymerization of actin filaments. Neither TA-993 nor MB3 affected cyclic AMP and cyclic GMP levels in resting platelets, and nor suppressed the increase in intracellular Ca(2+) concentration induced by ADP. These results suggest that the antiplatelet mechanisms of TA-993 and MB3 may involve inactivation of glycoprotein IIb/IIIa receptors via inhibition of the polymerization of actin.

T-686, a novel inhibitor of plasminogen activator inhibitor-1, inhibits thrombosis without impairment of hemostasis in rats

The aim of this study was to evaluate the antithrombotic potential of T-686 ((3E,4E)-3-benzylidene-4-(3,4,5-trimethoxy-benzylidene)-pyrr olidine-2,5-dione), a novel inhibitor of plasminogen activator inhibitor-1 (PAI-1), in rat thrombosis models. T-686 (0.1-100 mg/kg per day, p.o.) dose dependently decreased the weight of venous thrombi induced by a combination of stasis and hypercoagulability. The antithrombotic effect was enhanced by repeated administration of T-686. Warfarin (0.1 mg/kg per day for 3 days) also prevented thrombus formation. The antithrombotic action by warfarin was accompanied by prolongation of coagulation time, while no effect on coagulation time was observed in T-686-treated rats. T-686 lowered the activity of PAI-1 in plasma. In the arterio-venous shunt model, pretreatment with T-686 (10 mg/kg per day) or ticlopidine (100 mg/kg per day) for 8 days inhibited thrombus formation by 33% and 44%, respectively. T-686 had no effect on collagen-induced platelet aggregation ex vivo, while ticlopidine inhibited platelet aggregation. T-686 did not affect bleeding time at 10-100 times the antithrombotic dose, while warfarin dose dependently prolonged bleeding time at and around the antithrombotic dose. These results suggest that T-686 prevents thrombus formation in rats without impairment of hemostasis.

Inhibitory effects of TA-993, a new 1,5-benzothiazepine derivative, on platelet aggregation

TA-993, an l-cis 4',8-dimethyl derivative of the Ca2+ antagonist diltiazem, and some of its metabolites inhibited platelet aggregation induced by collagen, ADP, epinephrine, platelet activating factor, arachidonic acid, and U-46619 in human platelets in vitro. Among the metabolites, MB3 was the most potent (IC50, <1 micromol/L; several hundred times more potent than the parent compound). The d isomer of MB3 was >100 times less potent than the l isomer. Unlike acetylsalicylic acid (ASA), TA-993 inhibited both primary and secondary phases of ADP-induced platelet aggregation and also exhibited a disaggregating effect on human platelet aggregates. The inhibitory effect of TA-993 was enhanced when used in combination with ASA. In ex vivo studies involving rats, TA-993 (approximately 0.3 to 100 mg/kg PO) dose-dependently inhibited collagen-induced platelet aggregation (ED50, 3 mg/kg PO). In the whole-blood platelet aggregation system in rats, orally administered TA-993 was also inhibitory in single (3 to 30 mg/kg) or repeated daily (10 mg/kg per day for 10 days) dosage. Orally administered TA-993 dose-dependently inhibited ADP-induced platelet aggregation ex vivo in dogs (0.3 to 10 mg/kg), significantly protected mice against collagen + epinephrine-induced thromboembolic death (10 mg/kg), and inhibited thrombus formation in an arteriovenous shunt in rats (30 mg/kg). The Ca2+-antagonistic action of TA-993 was very weak in depolarized canine basilar arteries: the potency was approximately 1/10 that of diltiazem (d-cis) and d-TA-993. These results suggest that antiplatelet action is more characteristic of the l-cis than the d-cis 1,5-benzothiazepine structure and that TA-993 may become a clinically useful antiplatelet agent of this structure series.