August 8, 2007, Medscape
FDA Safety Changes for Levitra
Vardenafil (Levitra) Linked to Drug Interactions and Risk for Additive QT Effects
The (FDA) has approved safety labeling revisions to advise of drug interactions with vardenafil and the additive effect on QT interval prolongation associated with concomitant use of certain medications.
On April 6, the US Food and Drug Administration FDA approved safety labeling revisions for vardenafil (Levitra tablets, made by Bayer Pharmaceuticals Corp) to advise of drug interactions and the additive effect on QT interval prolongation associated with concomitant use of certain medications.
Because vardenafil is metabolized predominantly by the hepatic enzyme cytochrome P450 isoenzyme 3A4 (CYP3A4), serum levels can be significantly increased by concomitant use of indinavir, saquinavir, atazanavir, or other potent CYP3A4 inhibitors, such as clarithromycin, ketoconazole 400 mg daily, or itraconazole 400 mg daily. This can lead to an increased risk for adverse events such as hypotension, visual changes, and priapism.
Therefore, patients receiving treatment with these drugs or regimens should not exceed a dose of 2.5 mg vardenafil within a 24-hour period. For patients taking ketoconazole or itraconazole 200 mg daily, the vardenafil dose should not exceed 5 mg within a 24-hour period. The FDA notes that though the specific interactions have not been studied, other CYP3A4 inhibitors (eg, grapefruit juice) are also likely to increase vardenafil exposure.
The agency also warned of the risk for an additive effect on QT interval prolongation with concomitant use of other drugs known to exert this effect, as determined by data from a postmarketing study. A previous study of healthy men (n = 59) had revealed that the effect of 10 mg of vardenafil is similar to that of 400 mg of moxifloxacin.
These observations should be considered in clinical decisions when prescribing vardenafil for patients with a known history of QT prolongation or those taking medications known to prolong the QT interval. Patients taking class 1A (eg, quinidine, procainamide) or class III (eg, amiodarone, sotalol) antiarrhythmic medications or those with congenital QT prolongation should avoid using vardenafil.
Vardenafil is indicated for the treatment of erectile dysfunction. The recommended daily starting dose for most patients is 10 mg taken approximately 1 hour before sexual activity and then lowered to 5 mg or increased to a maximum of 20 mg based on efficacy and adverse events.
Pearls for Practice
· Because serum levels of vardenafil can be increased by potent CYP3A4 inhibitors and increase the risk for adverse events, patients receiving indinavir, saquinavir, atazanavir, clarithromycin, ketoconazole 400 mg daily, or itraconazole 400 mg daily should not take more than 2.5 mg of vardenafil within 24 hours. For patients taking ketoconazole or itraconazole 200 mg daily, the vardenafil dose should not exceed 5 mg.
· Vardenafil with certain other medications has an additive effect on QT interval prolongation. Postmarketing study data suggest that vardenafil and moxifloxacin have a similar effect.
News Author: Yael Waknine