Drug Interactions between belumosudil and dexamethasone / moxifloxacin

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 exposure to belumosudil, which is primarily metabolized by the isoenzyme. Concomitant use with the moderate CYP450 3A4 inducer, efavirenz, is predicted to decrease belumosudil peak plasma concentration (Cmax) and systemic exposure (AUC) by 32% and 35%, respectively, in healthy subjects. The interaction has not been studied with other, less potent inducers.

MANAGEMENT: The potential for diminished pharmacologic effects of belumosudil should be considered during coadministration with CYP450 3A4 inducers. Alternative treatments may be required if an interaction is suspected.