Tuesday, 12 November 2013

Rat Poison - here to stay for now

Dabigatran versus Warfarin in Patients with Mechanical Heart Valves — NEJM

Warfarin is rat poison. It is used to thin the blood (anticoagulation) of patients who are at risk of blood clot formation in their arteries or veins. Blood Clots can block and obstruct arteries or veins, or can fly off to places where you really do not want them to go, such as the brain causing a massive stroke.  The medical name for clot formation is thrombosis and for clots flying off is embolism.  The 2 words are often joined into a single word - thromboembolism.
The main advantage of warfarin is that it is cheap as chips - a few pence per tablet. It's main disadvantage is that the dose is not fixed but dependant on the result of a blood test. Therefore daily blood tests are required until the right dose is discovered - and that may take several days. The other big disadvantage of warfarin is the frequent interactions with other drugs and certain foodstuffs such as grapefruit juice - -these may change dose required i.e. more blood tests.
As a doctor I have always found that Warfarin is possibly one of the most awkward drugs to prescribe. I have always assumed it must be pretty awkward for patients to take - all those blood tests, all that uncertainty, all those interactions !
As a doctor looking after patients following cardiac surgery, I (or rather junior doctors under my tutelage) prescribe warfarin frequently to prevent thromboembolic events associated with new intracardiac prostheses or newly diagnosed atrial fibrillation. A warfarin prescription inevitably adds 3 to 5 days to a patient's length of hospital stay and we all know what that means nowadays - financial ruin of the nation and a nagging clinical director if you perform more valve operations than your colleagues!
This is why the results of the trial published recently (above) in the New England Journal were so disappointing to me.
Dabigatran is only one of the NOACs or novel anticoagulant drugs. They are so called because their mode of action is completely different from the mode of action of anticoagulant drugs used previously i.e.. warfarin or dicoumerol. In addition the dose is fixed and not dependant on any wretched blood test.
I just hope that this negative trial does not deter investigators to test all the other NOACs (4 with more on the developmental horizon) in post heart valve surgery patients. I just want to see the back of warfarin - period!