Ancrod, a drug derived from snake venom, is not effective in the treatment of ischaemic stroke if given within a 6 hour window after the onset of symptoms, according to the results of a randomised trial published in this weeks issue of The Lancet.
Ancrod contains a purified fraction of venom from the Malaysian pit viper. It is a promising biological agent that acts on bloods ability to clot. A previous trial has shown that ancrod has a favourable effect on ischaemic stroke when given within a 3 hour window.
In the European Stroke Treatment with Ancrod Trial (ESTAT), Michael Hennerici and colleagues assessed the effect of ancrod when given within 6 hours. The investigators randomly assigned 1222 patients from Europe, Australia, and Israel, ancrod (604) or a placebo (618). They found that functional ability was much the same in the active treatment group as in the control group. Neurological recovery was worse and there were more haemorrhages in the ancrod group than in the placebo group. Mortality at 3 months was higher in the ancrod group than in the placebo group but at 12 months there was no significant difference. The authors state that most patients were included beyond 3 hours after onset of stroke and this is likely to be the main reason that no benefit was shown for ancrod.
Professor Hennerici concludes: On the basis of our findings, ancrod should not be recommended for use in acute ischaemic stroke beyond 3 hours.