The Doctor’s Surgery
‘I am the only animal on the property that still takes warfarin regularly’
The River Wensum flows past my house and garden. Its banks are about fifty yards beyond our boundaries, no more than a stroll for the rats that haunt every riverside. A visit twice a year, autumn and spring, from the rat man ensured that no large colonies became established in my shrubberies or even, horror of horrors, in the roof.
Twenty-five years ago, the ratcatcher’s standard weapon was warfarin but, as the years passed, the rodents developed a resistance to it. Now there are several more lethal successors to warfarin, and I am the only animal on the property that still takes it regularly.
Taking a daily dose of warfarin is a nuisance. The dose has to be regularly monitored, as too much may cause a stroke or massive intestinal bleed. Erstwhile colleagues check my liability to a disastrous bleed and then alter the daily dose accordingly.
When I was in practice, I always recommended to patients on warfarin that they shouldn’t vary the nature of their diet, both solid and liquid. I suggested that they should take exactly the same amount of alcohol every day, regardless of what they were doing. Binges, induced by family celebrations, weddings or birthdays, summer barbecues or Christmas parties, were to be no more than a memory. Instead, whether sitting by their fire or dining out, they should enjoy the two or three units a day that were now de rigueur.
The solid diet also needs to be modified. I no longer need to find an excuse for not eating spinach or broccoli – for I only have to plead that they and some other green vegetables are not compatible with my rat poison. This is true: they contain vitamin K, which counteracts warfarin, whereas alcohol enhances its action. Other less pleasing dietary rules must also be followed.
Fortunately, when starting on warfarin, the patient’s doctor gives them a pamphlet on dos and don’ts for this type of anticoagulation.
Who needs anticoagulants? Every patient whose heart is irregularly irregular may well be fibrillating. Atrial fibrillation renders someone much more likely to have a stroke. The most common cause of stroke is a clot blocking one of the blood vessels leading to the brain. Conversely, too much warfarin may induce a stroke from a cerebral haemorrhage. Too little warfarin and the patient may suffer a clot-induced stroke; too much of it and they may have one from a bleed. It’s a fine line – hence the need for regular blood tests.
Over the past few years, other forms of oral anticoagulants for the prevention of clot-induced strokes in atrial fibrillation have been tried. Their disadvantage is that, if there is evidence of a cerebral bleed, the usual treatment of vitamin K will not be effective.
Another problem is that the new DOACS (direct-acting oral anticoagulants) can have a deleterious effect on kidney function, and many patients with heart problems often have poor renal function. On 2nd December last year, the BMJ published the results, comparing the advantages and disadvantage of DOACS with those of warfarin. The research – undertaken by López-lópez and colleagues – concluded that DOACS are in general safer than warfarin; of the DOACS available, apixaban 5mg twice daily and dabigatran 150mg twice daily, were the treatment of choice.
The BMJ, while commending this research work, did suggest that other factors which could be peculiar to a particular patient also had to be taken into consideration. They concluded that apixaban 5mg twice daily ranked the highest of DOACS in most cases and was also the most cost-effective when compared with warfarin.
I, like my possible resident rats, may soon be deserting warfarin – for an oral anticoagulant. I will discuss with my doctor the advantages of a DOAC in comparison with warfarin.