The alternative to warfarin: how much to prescribe
| 26 January, 2011 | Richard P. Grant |
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One of our highest ranked papers discusses a randomized trial looking at a long-sought after orally administered substitute for warfarin in reducing the risk of embolic events in cases of atrial fibrillation. The paper, which finds dabigatran to be a promising alternative (warfarin is extremely good, but has a narrow therapeutic range and is cumbersome to use, necessitating constant monitoring of levels in the patient’s blood) has attracted 14 evaluations over five months.
It’s also attracted a dissent: Patrice Forget and Marc De Kock of UCL Saint Luc are concerned about altered renal function in patients taking dabigatran, and how the paper doesn’t detail the proportion of discontinuation in the trial due to acute renal failure. This is important, they say, because identifying patients with impaired renal function might identify sub-groups of the population at increased risk of adverse side-effects.
Faculty Member Wilbert Aronow at the New York Medical College, has now responded to the dissent, using our shiny new commenting system. He helpfully points out that the FDA has actually approved two doses of dabigatran, including a lower one (75 mg twice daily) for instances of severe chronic kidney disease.
No doubt we’ll hear more about this, but it’s good to see much-maligned systems working as intended!
Edited to add: if you’re interested in oral anticoagulants etc., you could do worse than check out this (open access) F1000 Reports article, Post-operative thromboprophylaxis: new oral thrombin and factor X inhibitors and their place in clinical practice, DOI: 10.3410/M2-37.
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I’m not sure whether primary care physicians are aware of how many cases of toxicity occur, or how many are also associated with morbidity (e.g., pneumonia) and mortality. I look forward to learning more about this alternative, even though I am only indirectly involved in my capacity of a clinical laboratory scientist, who has frequently reported critical PT / INR values during my 35 years experience.
The FDA has approved many things that were later withdrawn for morbidity and mortality issues. The FDA’s two dose approval does not address the issue of not detailing the proportion of discontinuation in the trial due to acute renal failure. This issue of unreported discontinuation is a major ethical criticism of Pharma-designed and reported drug trials.
Vitamin E moderately prolongs prothrombin clotting time, decreases platelet adhesion, and has a limited “blood thinning” effect. This is the reason behind the Shutes’ using vitamin E (1,000 – 2,000 IU/day) for thrombophlebitis and related conditions.