Adverse Event Reports For This New Blood Thinner Drug May Exceed Pre-Approval Clinical Trial Observations
In early December 2011 the FDA announced it is evaluating reports of bleeding in patients taking Pradaxa (dabigatran etexilate mesylate) that have been submitted to the agency's Adverse Events Reporting System (AERS) database to determine whether serious side effects are occurring at a higher rate than would be expected.
Pradaxa is a relatively new blood thinner, or anticoagulant, medication used to reduce the risk of stroke in patients with non-valvular atrial fibrillation (AF). It has been available for use in the US since October 2010.
As background regarding this emerging drug safety issue, in mid-October 2011 we wrote an article, "New Heart Drug Pradaxa May Be Sending "Early" Drug Safety Signals", about how hemorrhages and thromboembolic events had been reported to the FDA at an unusually high rate, according to a report from the Institute for Safe Medication Practices (ISMP).
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Then, in mid-November 2011 a Reuters news article, "Boehringer says about 260 deaths related to Pradaxa", provided this relevant information:
Boehringer Ingelheim said that 260 cases of fatal bleeding have been linked to its new stroke prevention pill Pradaxa so far, adding that the risk of death was still below the rate that emerged in the clinical trial that led to the drug's approval.
From the "FDA Drug Safety Communication: Safety review of post-market reports of serious bleeding events with the anticoagulant Pradaxa (dabigatran etexilate mesylate)" issued December 7, 2011 by the FDA about their current evaluation concerning the safety of Pradaxa:
Complicating this analysis, many factors can influence whether or not adverse effects are reported, particularly the length of time a drug has been marketed, whether or not the adverse effect is described in the drug label, and the amount of publicity about an event or safety concern.
For patients with non-valvular AF, the main alternative to Pradaxa is warfarin. Because warfarin has been marketed for over 50 years and is well-known to cause bleeding, patients and healthcare professionals are not likely to report bleeding in association with warfarin. Thus, a simple comparison between Pradaxa and warfarin with respect to the numbers of post-marketing reports of bleeding is of limited value.
FDA is working with the manufacturer, Boehringer Ingelheim, to analyze the post-market reports for evidence of inappropriate dosing, use of interacting drugs, or other clinical factors that might lead to a bleeding event.
FDA is also using its Mini-Sentinel active surveillance system to compare new users of Pradaxa and warfarin with respect to the likelihood of being hospitalized for bleeding.
It is very important to note, as pointed out in the December 7, 2011 FDA MedWatch email alert about this Pradaxa Drug Safety Communication:
Patients with AF should not stop taking Pradaxa without talking to their healthcare professional. Stopping use of blood thinning medications can increase their risk of stroke. Strokes can lead to permanent disability and death.
The FDA has said it will communicate any new drug-safety information concerning the risk of bleeding in patients using Pradaxa when it becomes available.
We will be watching for any new drug information updates from the FDA regarding the safety of Pradaxa and will report significant developments, here.
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