Pharmacokinetics and pharmacodynamics of sibrafiban alone or in combination with ticlopidine and aspirin

Inhibitory effect on human platelet aggregation and coagulation and antioxidant activity of C. edulis Ker Gawl rhizome and its secondary metabolites

ETHNOPHARMACOLOGICAL RELEVANCE

Although Canna edulis Ker Gawl rhizome has been used in Traditional Vietnamese Medicine to prevent and treat heart diseases without thorough scientific evidence, limited intensive search for the bioactivities and useful substances has been done.

AIM OF THE STUDY

This study aims to investigate the antiplatelet aggregation, anticoagulant and antioxidant activity of extracts from C. edulis rhizome, separate and purify its compounds from the most active fraction and evaluate the antiplatelet aggregation, anticoagulant and antioxidant activity of isolated compounds.

MATERIALS AND METHODS

C. edulis rhizome was extracted with ethanol, then fractionated with n-hexane, ethyl acetate and water. The inhibitory effect on adenosine diphosphate- and collagen-induced human platelet aggregation was evaluated. Prothrombin time, activated partial thromboplastine time and thrombine time were measured to examine the anticoagulant activity. The free radical scavenging ability was assessed with DPPH and ABTS assays. The fraction that showed the most active was used to separate and purify compounds. The structures of compounds were elucidated by NMR and MS spectroscopic methods. Isolated compounds were also tested for antiplatelet, anticoagulant and antioxidant activity.

RESULTS

The ethyl acetate fraction showed the most potent antiplatelet aggregation, anticoagulant and antioxidant activity. Subsequent fractionation of this active fraction resulted in the isolation of seven known compounds: 5-hydroxy-6-methyl-2H-pyran-2-one (1), epimedokoreanone A (2), nepetoidin B (3), ferulic acid (4), caffeic acid (5), hydroxytyrosol (6), and 1H-indole-3-carboxaldehyde (7). Previous studies reported the antiplatelet, anticoagulant and antioxidant activity of ferulic acid (4), caffeic acid (5) and hydroxytyrosol (6) and the antioxidant activity of nepetoidin B (3). This study demonstrated that both epimedokoreanone A (2) and nepetoidine B (3) also exhibited good antiplatelet effect and epimedokoreanone A (2) also had effective anticoagulant and antioxidant activity, while 5-hydroxy-6-methyl-2H-pyran-2-one (1) showed weaker antiplatelet and antioxidant activity but no anticoagulant effect.

CONCLUSIONS

This is the first experimental study to demonstrate the potent dose-dependent antiplatelet aggregation, anticoagulant and antioxidant activity of C. edulis rhizome and its pure compounds, supporting the traditional use of this plant for the treatment of heart diseases. The C. edulis rhizome is a potential source of bioactive compounds or functional food for treatment and/or prevention of heart- and oxidative stress-related diseases and its bioactive compounds are good candidates for drug development of anti-thrombosis and antioxidant agents.

Inhibition of platelet aggregation by aspirin progressively decreases in long-term treated patients

OBJECTIVES

We sought to investigate, during a two-year follow-up period, the effects of aspirin on platelet aggregation.

BACKGROUND

The platelets of patients given aspirin may be less sensitive to antiplatelet treatment, although the extent of such phenomenon over long-term follow-up is unclear.

METHODS

Adenosine diphosphate (ADP) and collagen-induced platelet aggregation was periodically monitored before and after 2, 6, 12, and 24 months of treatment with aspirin (n = 150) or ticlopidine (n = 80) in patients matched for gender, age, and risk factors for atherothrombosis.

RESULTS

Compared with baseline values, two months of aspirin treatment significantly inhibited platelet aggregation; thereafter, this inhibitory effect progressively decreased. At 24-month follow-up, collagen-induced platelet aggregation was significantly higher than that observed at two months (p < 0.05); a more pronounced difference was observed when collagen-induced lag phase was considered (p < 0.01). Restoration of platelet aggregation was less evident when ADP was used as an agonist. Conversely, the inhibition induced by ticlopidine was constant throughout follow-up with both agonists.

CONCLUSIONS

The study demonstrates that a long-term treatment with aspirin is associated with a progressive reduction in platelet sensitivity to this drug.

Pharmacodynamic characterization of the interaction between the glycoprotein IIb/IIIa inhibitor YM337 and unfractionated heparin and aspirin in humans

AIMS

To investigate the pharmacodynamic interaction of unfractionated heparin (UFH) and acetylic salicylic acid (ASA) on YM337, a monoclonal humanized antibody of the platelet GPIIb/IIIa receptor.

METHODS

In a randomized, placebo-controlled study three treatment groups each with six healthy volunteers received the following medication: group 1, ASA (3 days) + UFH + YM337 (placebo); group 2, ASA (placebo) + UFH (placebo) + YM337; group 3, ASA + UFH + YM337. Assessments were made over 24 h and included bleeding time (BT), ADP (20 microm)- and collagen (5 microg ml-1)-induced platelet aggregation and PAC1 and CD62 expression measured by flow cytometry.

RESULTS

In group 3 BT was prolonged to 35 [median, 16-45 min (1,3 quartile)] after UFH administration, increasing to 45 [median, 42-45 min (1,3 quartile)] after YM infusion (6 h). BT remained elevated to 26 [median, 14-45 min (1,3 quartile)] at 24 h, while groups 1 and 2 returned to normal values. Collagen-induced aggregation was 73% [median, 70-80% (1,3 quartile)] under YM337 alone, 79% [median, 72-80% (1,3 quartile)] under ASA + UFH and reduced only in group 3 to 24% [median, 18-29% (1,3 quartile)]. In both groups receiving active YM337, PAC1 expression showed a reduction to < 20% after 6 h of infusion. CD62 expression was not significantly affected by any treatment.

CONCLUSION

UFH and YM337 have strong synergistic effects on BT, while coadministration of ASA strongly augments inhibitory effects of YM337 on collagen-induced platelet aggregation.