Drug Interactions between dexamethasone / moxifloxacin and ixabepilone

MONITOR CLOSELY: Concomitant administration of corticosteroids may potentiate the risk of tendinitis and tendon rupture associated with fluoroquinolone treatment. The mechanism is unknown. Tendinitis and tendon rupture have most frequently involved the Achilles tendon, although cases involving the rotator cuff (the shoulder), the hand, the biceps, and the thumb have also been reported. Some have required surgical repair or resulted in prolonged disability. Tendon rupture can occur during or up to several months after completion of fluoroquinolone therapy.

MANAGEMENT: Caution is recommended if fluoroquinolones are prescribed in combination with corticosteroids, particularly in patients with other concomitant risk factors (e.g., age over 60 years; recipient of kidney, heart, and/or lung transplant). Patients should be advised to stop taking the fluoroquinolone, avoid exercise and use of the affected area, and promptly contact their physician if they experience pain, swelling, or inflammation of a tendon. In general, fluoroquinolones should only be used to treat conditions that are proven or strongly suspected to be caused by bacteria and only if the benefits outweigh the risks.

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of ixabepilone, which is primarily metabolized by the isoenzyme. According to the manufacturer, coadministration of ixabepilone with the potent CYP450 3A4 inducer rifampin decreased ixabepilone systemic exposure (AUC) by 43% compared to administration of ixabepilone alone. Reduced efficacy of ixabepilone may occur. However, the extent to which less potent CYP450 3A4 inducers interact with ixabepilone is unknown.

MANAGEMENT: The potential for diminished pharmacologic effects of ixabepilone should be considered during coadministration with CYP450 3A4 inducers. Caution is advised if they are used with ixabepilone, and alternative treatments may be required if an interaction is suspected.