Effects of Etamsylate on Platelet Functions and Arachidonic Acid Metabolism

Ethamsylate for the prevention of morbidity and mortality in preterm or very low birth weight infants

BACKGROUND

Ethamsylate decreases blood loss in certain clinical situations such as menorrhagia and following some surgical procedures. This potential to reduce bleeding has led to the hypothesis that it may have a role to play in reducing intraventricular haemorrhage in preterm infants.

OBJECTIVES

To determine if ethamsylate, when compared to placebo or no treatment, reduces morbidity and/or mortality in preterm infants.

SEARCH STRATEGY

We searched the Cochrane Neonatal Group Trials Register (24 August 2009), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2009, Issue 2), MEDLINE and EMBASE (January 1966 to July 2009) and the Oxford Database of Perinatal Trials.

SELECTION CRITERIA

Randomised controlled trials or quasi-randomised trials comparing ethamsylate with placebo or no treatment. The initial search for trials enrolling infants born less than 32 weeks gestation was subsequently expanded to include trials enrolling preterm infants < 35 weeks gestation or < 2000 grams birth weight. Studies were included if they reported on outcomes of all children until death or discharge home. Data from reports of neurodevelopmental follow-up were only included if at least 80% of participants were followed up.

DATA COLLECTION AND ANALYSIS

Both review authors independently assessed trial quality and extracted data. We calculated relative risk (RR) and risk difference (RD) together with 95% confidence intervals (CI) and used a fixed-effect model for meta-analysis.

MAIN RESULTS

Eight studies were identified but only seven trials enrolling 1410 preterm infants were located. There was no significant difference detected in neonatal mortality or neurodevelopmental outcome at two years between infants treated with ethamsylate and controls. Infants treated with ethamsylate had significantly less intraventricular haemorrhage than controls at < 31 weeks (typical RR 0.63, 95% CI 0.47 to 0.86) and < 35 weeks gestation (typical RR 0.77, 0.65 to 0.92). There was also a significant reduction in grade 3 and 4 intraventricular haemorrhage when all infants < 35 weeks gestation (typical RR 0.67, 95% CI 0.49 to 0.94) were analysed as a single group, but not for the group of infants < 32 weeks alone. There was a reduction in symptomatic patent ductus arteriosus at < 31 weeks gestation (typical RR 0.32, 95% CI 0.12 to 0.87). There were no adverse effects of ethamsylate identified from this systematic review.

AUTHORS' CONCLUSIONS

Preterm infants treated with ethamsylate showed no reductions in mortality or neurodevelopmental impairment despite the reduction in any grade of intraventricular haemorrhage seen in infants < 35 weeks gestation.

Therapeutic efficacy and mechanism of action of ethamsylate, a long-standing hemostatic agent

Ethamsylate (2,5-dihydroxy-benzene-sulfonate diethylammonium salt) is a synthetic hemostatic drug indicated in cases of capillary bleeding. This review covers more than 40 years of intensive clinical and fundamental research with ethamsylate. First, we summarize the large medical literature concerning its clinical efficacy. Of these, well-controlled clinical trials clearly showed the therapeutic efficacy of ethamsylate in dysfunctional uterine bleeding, with the magnitude of blood-loss reduction being directly proportional to the severity of the menorrhagia. Other well-controlled clinical trials showed therapeutic efficacy of ethamsylate in periventricular hemorrhage in very low birth weight babies and surgical or postsurgical capillary bleeding. Second, we review the numerous investigations performed to elucidate the mechanism of action of ethamsylate. Ethamsylate acts on the first step of hemostasis by improving platelet adhesiveness and restoring capillary resistance. Recent studies showed that ethamsylate promotes P-selectin-dependent, platelet adhesive mechanisms. Finally, we compare ethamsylate with other recent hemostatic agents. It is suggested that the place of ethamsylate as a hemostatic agent is that of a mild but well-tolerated drug, particularly useful in dysfunctional uterine bleeding when contraception is not needed.

Effects of etamsylate on equine platelets: in vitro and in vivo studies

The aim of this study was to investigate whether etamsylate produces equine platelet activation. In vitro and in vivo studies were designed in which seven and eight adult healthy horses were included, respectively. In the in vitro study, citrated blood was incubated with different concentrations of etamsylate, and P-selectin expression and annexin V binding were determined by flow cytometry. In the in vivo study, blood was collected before and 1 and 2h after IV administration of etamsylate, and P-selectin expression was evaluated. In the in vitro study, a significant increase in P-selectin expression, leukocyte-platelet aggregate formation and annexin V binding were observed. In the in vivo study, a marked increase in P-selectin expression and heterotypic aggregate formation was seen in two and five horses, respectively, although no significant differences were detected when analyzing results from all the animals together. The results of the in vitro study indicate that etamsylate produces a pre-activation state in equine platelets, but this fact could be confirmed by the in vivo study.

The hemostatic agent ethamsylate promotes platelet/leukocyte aggregate formation in a model of vascular injury

The hemostatic agent ethamsylate enhances membrane expression of P-selectin in human platelets, but whether this promotes platelet-leukocyte aggregate formation is unknown. Here we investigated this point by flow cytometry determination of human platelet-leukocyte aggregates under basal conditions and after whole-blood perfusion through a damaged rabbit aorta segment. Actions of ethamsylate on adhesive molecules of platelets and leukocytes were investigated in parallel. Under basal conditions, ethamsylate was unable to modify whole-blood platelet-leukocyte aggregation, but following whole-blood perfusion through a damaged vessel, ethamsylate produced a modest, but significant increase in platelet-leukocyte aggregates (48+/-21 and 45+/-26% above control levels at ethamsylate 20 and 40 microm respectively). In isolated leukocyte plasma membranes, 14C-ethamsylate specifically bound up to an amount of 660 pmol/mg protein. Moreover, at concentrations > or =1 microm, ethamsylate induced an important (100-200%) and significant increase in the P-selectin glycoprotein ligand 1 (PSGL-1) fluorescence signal in isolated leukocytes and was unable to significantly modify the percentage of CD11b-positive cells. However, no significant changes in aggregate formation were found when ethamsylate was incubated with isolated leukocytes and blood was reconstituted and perfused. In isolated platelet cell membranes, anti-P-selectin antibody and the anti-integrin RGD-containing pentapeptide (GRDGS) were unable to displace 14C-ethamsylate binding. In conclusion, ethamsylate specifically binds to plasma membranes of leukocytes, enhances membrane PSGL-1 expression and promotes leukocyte-platelet aggregation in whole-blood perfused through a damaged vascular segment. These results together with the previously observed enhancement of platelet P-selectin membrane expression [Thromb. Res. (2002)107:329-335] confirms and extends the view that ethamsylate acts on the first step of hemostasis, by improving platelet homo- and heterotypic adhesiveness.

The hemostatic agent ethamsylate enhances P-selectin membrane expression in human platelets and cultured endothelial cells

Ethamsylate possesses antihemorrhagic properties, but whether or not it directly activates blood platelets is unclear. Here we investigated the platelet activation potential of ethamsylate, by measuring membrane P-selectin expression with flow cytometry in human whole blood and also by immunofluorescence imaging of isolated human platelets. Moreover, we measured membrane P-selectin expression in the SV40-transformed aortic rat endothelial cell line (SVAREC) and 14C-ethamsylate membrane binding and/or uptake in platelets and endothelial cells. Whole blood flow cytometry showed a modest, but statistically significant increase by ethamsylate in the percentage of platelets expressing P-selectin (from 2% to 4-5%, p < 0.05). Immunofluorescence showed a sizable (39%) and significant (p < 0.01) enhancement of P-selectin expression at the lowest concentration of ethamsylate tested (1 microM), with maximal enhancement of P-selectin expression (75-90%) at 10 microM ethamsylate. Similar results were obtained in SVAREC endothelial cells. 14C-ethamsylate specifically bound to platelets and endothelial cell membranes, without significant uptake into the cell interior. In conclusion, ethamsylate enhances membrane P-selectin expression in human platelets and in cultured endothelial cells. Ethamsylate specifically binds to some protein receptor in platelet and endothelial cell membranes, receptor which can signal for membrane P-selectin expression. These results support the view that ethamsylate acts on the first step of hemostasis, by improving platelet adhesiveness and restoring capillary resistance.

Thrombogenic effects of xenobiotics

The mechanisms by which xenobiotics may cause or promote thrombosis include vascular damage, induction of a hypercoagulable state and disturbances of blood flow. This paper discusses the methods available to detect various types of thrombogenic substances. Pathomorphological techniques are best suited to demonstrate thrombosis caused by localized vascular damage or generalized endothelial lesions. For the assessment of disseminated microcirculatory thrombosis, the consumption of platelets and clotting factors and the appearance of specific platelet proteins and fibrinogen and fibrin split products can be determined in the blood. Hypercoagulability which is defined as a perturbation of the hemostatic equilibrium resulting in a shift in the direction of thrombosis, is of particular importance in toxicology. Many in vitro, ex vivo and in vivo methods have been proposed to detect and to measure the ability of xenobiotics to induce a prethrombotic state. Their usefulness is demonstrated with several examples.