An 89-year-old woman was admitted to hospital with melaena. She had a history of atrial fibrillation, type 2 diabetes complicated by hypertension, ischaemic heart disease and nephropathy (creatinine clearance of 29 mL/min, using the Cockcroft-Gault equation).
The patient was taking several drugs for her conditions. These included warfarin which she had taken for 12 years, without any adverse events. Three weeks before admission she was switched to dabigatran, 110 mg twice a day, for prevention of stroke in association with atrial fibrillation.
On admission, her serum creatinine was elevated (172 micromol/L with an estimated creatinine clearance of 18 mL/min) and her haemoglobin was 61 g/L. Despite warfarin therapy ceasing three weeks earlier, the INR was 2.5 and the activated partial thromboplastin time (aPTT) was 84 seconds (normal range 25–35 seconds).
There is no specific antidote for dabigatran. She was given fresh frozen plasma, vitamin K and six units of packed red cells.1 Upper gastrointestinal endoscopy found no pathology and the bleeding settled spontaneously.
The patient required prolonged rehabilitation after the haemorrhage. She was not discharged home until two months later.
This case highlights the dangers of switching patients stabilised on treatment to newer therapies, especially if there are few data on safety and effectiveness in a particular group of patients. The risk of a drug in ‘real world’ use is often underestimated in clinical trials, as they are often designed to demonstrate efficacy rather than test safety. The trials generally study a highly selected patient group – with a long list of exclusions designed to mitigate risk – and the patients are intensively followed in a manner not typically feasible in routine practice. The true risk of a drug is generally unclear until there is considerable postmarketing experience.
- Levi M, Eerenberg E, Kamphuisen PW. Bleeding risk and reversal strategies for old and new anticoagulants and antiplatelet agents. J Thromb Haemost 2011;9:1705-12.
- Dabigatran (Pradaxa): risk of bleeding relating to use. Therapeutic Goods Administration. 2011. www.tga.gov.au/safety/alerts-medicine-dabigatran-111005.htm [cited 2012 Mar 6]
- European Medicines Agency updates on safety of Pradaxa. European Medicines Agency. 2011. www.ema.europa.eu/docs/en_GB/document_library/Press_release/2011/11/WC500117818.pdf [cited 2012 Mar 6]
- FDA Drug Safety Communication. Safety review of post-market reports of serious bleeding events with the anticoagulant Pradaxa (dabigatran etexilate mesylate). 2011. www.fda.gov/Drugs/DrugSafety/ucm282724.htm [cited 2012 Mar 6]
- Safe and Quality Use of Medicines and the Anticoagulant Working Party. Guidelines for managing patients on dabigatran (Pradaxa) who present to hospital. Queensland Health. 2011. www.health.qld.gov.au/qhcss/mapsu/documents/dabigatran_info.pdf [cited 2012 Mar 6]
- Connolly SJ, Ezekowitz MB, Yusuf S, Eikelboom J, Oldgren J, Parekh A, et al. Dabigatran versus warfarin in patients with atrial fibrillation. N Engl J Med 2009;361:1139-51.
- Eikelboom JW, Wallentin L,Connolly SJ, Ezekowitz M, Healey JS,Oldgren J, et al. Risk of bleeding with 2 doses of dabigatran compared with warfarin in older and younger patients with atrial fibrillation: an analysis of the randomized evaluation of long-term anticoagulant therapy (RE-LY) trial. Circulation 2011;123:2363-72.
- Boehringer-Ingelheim US corporate website: Dabigatran. RELY-ABLE Trial Emergency Information. 2011. www.rely-able-trial.com/Rely2Web/resources/jsp/emergency/dabigatran_bg.jsp [cited 2012 Mar 6]
- Al-Sallami HS, Barras MA, Green B, Duffall SB. Routine plasma anti-Xa monitoring is required for low-molecular-weight heparins. Clin Pharmacokinet 2010;49:567-71.
- Brighton T. New oral anticoagulant drugs – mechanisms of action. Aust Prescr 2011;33:38-41.
- Hankey GL, Eikelboom JW. Dabigatran etexilate: a new oral thrombin inhibitor. Circulation 2011;123:1436-50.