Drugs Xagena
Pradaxa is a medicine that contains the active substance Dabigatran etexilate; it is used to prevent the formation of blood clots in the veins in adults who have had an operation to replace a hip or knee.
It is also used to prevent stroke and the formation of clots in adults who have non-valvular atrial fibrillation and are considered to be at risk of stroke.
Pradaxa is available as capsules ( 75, 110 and 150 mg ).
The capsules should be swallowed whole with water. For patients who have had a hip or knee replacement, treatment with Pradaxa should start with one 110 mg capsule taken one to four hours after the end of the operation. Treatment then continues with 220 mg ( as two 110 mg capsules ) once a day for 28 to 35 days after hip replacement and for 10 days after knee replacement. The start of the treatment should be delayed in patients who are still bleeding from the site of surgery. If treatment is not started on the day of the operation, it should start at 220 mg ( as two 110 mg capsules ) once a day. A lower dose is used in patients with moderately reduced kidney function, in patients over 75 years of age, and in patients also taking Amiodarone ( Cordarone ), Quinidine or Verapamil ( Isoptin ).
For the prevention of stroke and blood clots in patients with non-valvular atrial fibrillation, Pradaxa is taken at a dose of 300 mg ( as one 150 mg capsule twice a day ) and should be taken long term. A lower dose should be used in patients aged over 80 years and in patients also taking Verapamil. A lower dose may also be considered in patients aged 75 to 80 years, patients with moderately reduced kidney function, patients with gastritis, oesophagitis or gastroesophageal reflux and other patients who are at increased risk of bleeding.
All patients considered to be at increased risk of bleeding should be monitored closely and the dose of Pradaxa lowered at the discretion of the physician.
In all patients, kidney function should be assessed before starting treatment to exclude patients with severely reduced kidney function, and should be re-assessed during treatment if any worsening is suspected. When Pradaxa is used long term in patients with non-valvular atrial fibrillation, kidney function should be assessed at least once a year if their kidney function is mildly to moderately reduced or if they are over 75 years old.
Patients undergoing hip or knee replacement surgery are at a high risk of blood clots forming in their leg veins. These clots, which include deep vein thrombosis ( DVT ), can be dangerous if they move to another part of the body such as the lungs. Patients who have atrial fibrillation are also at risk of blood clots which can travel to the brain and cause a stroke.
The active substance in Pradaxa, Dabigatran etexilate, is a prodrug of Dabigatran. This means that it is converted into Dabigatran in the body. Dabigatran is an anticoagulant; it blocks thrombin, which is central to the process of blood clotting.
Two main studies have been performed to compare Pradaxa ( either 220 or 150 mg a day ) with Enoxaparin ( Clexane, Lovenox ) in patients who had undergone a hip or knee replacement. The first study involved a total of 2,101 patients who had had a knee replacement operation, and the second involved a total of 3,494 patients who had had a hip replacement.
In both studies, the main measure of effectiveness was based on the number of patients who had blood clots forming in the veins or who died of any cause during the treatment period. In most cases, blood clot formation was detected using scans of the veins or by looking for signs of blood clots in the lungs.
A third main study compared Pradaxa ( 110 mg and 150 mg twice a day ) with Warfarin ( Coumadin ) in around 18,000 adult patients with non-valvular atrial fibrillation who were considered to be at risk of stroke. The patients were treated for one to three years and the main measure of effectiveness was based on the number of patients who had a stroke or a blood clot blocking blood vessels in other parts of the body.
Pradaxa was as effective as Enoxaparin in preventing the formation of blood clots or death. In the study of patients undergoing knee replacement, blood clots were detected in 36% of the patients taking the 220 mg dose of Pradaxa ( 182 out of 503 ), compared with 38% of the patients receiving Enoxaparin ( 192 out of 512 ). There was one death in each group ( less than 1% ).
In the study of patients undergoing hip replacement, blood clots were detected in 6% of the patients taking 220 mg Pradaxa ( 50 out of 880 ), compared with 7% of the patients receiving Enoxaparin ( 60 out of 897 ). Three patients in the Pradaxa group died ( less than 1% ), but two of these deaths were unrelated to blood clots. In the hip and knee studies, there was some evidence that the 220 mg dose may be more effective than the 150 mg dose.
The study in patients with non-valvular atrial fibrillation showed that around 1.5% of patients taking Pradaxa 110 mg ( 183 patients out of 6,015 ) and 1.1% of patients taking Pradaxa 150 mg ( 134 out of 6,076 ) had a stroke or other problems caused by blood clots, compared with 1.7% of those taking Warfarin ( 202 out of 6,022 ).
The most common side effect with Pradaxa ( seen in more than one patient in 10 ) is bleeding.
Pradaxa must not be used in people who are hypersensitive ( allergic ) to Dabigatran etexilate or any of the other ingredients. It must not be used in patients who have severely reduced kidney function, who are currently bleeding significantly or who have a condition putting them at risk of major bleeding. It must not be used in patients taking any other anticoagulant medicine, except in specific situations such as when the patient is being switched to or from Pradaxa.
Pradaxa must also not be used in patients with serious liver problems or patients taking by mouth or injection the medicines against fungal infections Ketoconazole ( Nizoral ) and Itraconazole ( Sporanox ), the immunosuppressant medicines Ciclosporin ( Sandimmune ) and Tacrolimus ( Prograf ) or Dronedarone ( Multaq ).
The CHMP noted that effect of Pradaxa in preventing the formation of blood clots patients who have undergone a hip or knee replacement is comparable to that of Enoxaparin. Pradaxa, which is taken by mouth, has the advantage of being more convenient for patients.
The CHMP also noted that Pradaxa compared well with Warfarin in reducing the risk of strokes in patients with atrial fibrillation without increasing the risk of major bleeding. Since certain patients are at increased risk of bleeding, a number of precautions were included in the prescribing information. ( Xagena )
Source: European Medicines Agency ( EMA ), 2013
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