No agent can reverse action of blood thinner

A leading stroke physician and Tallaght hospital consultant Dr Ronan Collins has challenged the manner in which the Health Service Executive's medicines management programme recently advised doctors to exercise caution in the use of a new generation of blood-thinning drugs.

Its clinical lead, Prof Michael Barry, had written to doctors warning them that the risk of gastrointestinal haemorrhage from the novel agents may be even greater than with warfarin, a long-established treatment for people with blood clots and those at risk of developing clots from other medical conditions.

Improvement
More than 13,000 patients receive treatment with novel anticoagulants – new oral anticoagulants (NOAC) – drugs in the Republic. Pradaxa (dabigatran) and Xarelto (rivoraxaban) have been developed as an improvement on warfarin by providing a more predictable anticoagulant effect and one that didn't require frequent monitoring in the form of regular blood tests. The new-generation blood thinners also cause less drug interactions, and are less likely to cause brain haemorrhage as a side effect.

Major clinical trials have shown the new drugs are as effective or better at preventing strokes than warfarin.

The advent of the newer agents coincided with a renewed emphasis on the link between stroke and a heart rhythm abnormality called atrial fibrillation. In this condition, clots are flicked off by the heart to the brain. Atrial fibrillation affects about 1 per cent of the population, rising to 10 per cent in people over the age of 80.

Because it increases the risk of a stroke by a factor of five, atrial fibrillation is an obvious target to reduce the almost 10,000 strokes that affect people in Ireland each year. But because of warfarin's risks and side-effects, many patients decide against starting the drug. It is generally accepted that the NOACs are "cleaner" drugs than warfarin.

Drawback
However, they have one major potential drawback – we do not yet have an agent that can reverse their blood-thinning action in an emergency. So if, for example, a person requires unplanned urgent surgery, a potential dilemma arises: does the surgeon go ahead and face dealing with extensive bleeding during the operation or does he "sit" on an already ill patient waiting for the NOAC to flush out of their system?

Or if someone taking one of the newer drugs presents with a major gastric bleed, how difficult will it be to reverse the bleeding? By the very nature of its action, taking any anticoagulant brings with it the risk of unwanted bleeding. A crucial factor in prevention is to prescribe the drug cautiously, at the correct dose while keeping a sharp eye open for interactions with other drugs the patient may be taking.