On April 6, the FDA approved safety labeling revisions for vardenafil - levitra (Levitra tablets, made by Bayer Pharmaceuticals Corp,levitra information) to advise of drug interactions and the additive effect on QT interval prolongation associated with concomitant use of certain medications. Because vardenafil - levitra is metabolized predominantly by the hepatic enzyme cytochrome P450 isoenzyme 3A4 (CYP3A4,levitra information), 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 - levitra within a 24-hour period. For patients taking ketoconazole or itraconazole 200 mg daily, the vardenafil - levitra 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,levitra information) are also likely to increase vardenafil - levitra 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 - levitra is similar to that of 400 mg of moxifloxacin.

These observations should be considered in clinical decisions when prescribing vardenafil - levitra 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,levitra information) or class III (eg, amiodarone, sotalol,levitra information) antiarrhythmic medications or those with congenital QT prolongation should avoid using vardenafil - levitra.

vardenafil - levitra 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.