Drug Interactions between melatonin and moxifloxacin / triamcinolone

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 inhibitors of CYP450 1A2 may substantially increase the plasma concentrations of melatonin. Data from available studies suggest that melatonin is primarily metabolized by CYP450 1A2, with possible contribution from CYP450 2C19 and 2C9. Coadministration of fluvoxamine, a potent CYP450 1A2 inhibitor that also inhibits CYP450 2C19 and 2C9, increased melatonin systemic exposure (AUC) by 17-fold and maximum plasma concentration (Cmax) by 12-fold. Contraceptives containing ethinyl estradiol, which can inhibit CYP450 1A2, may lead to a 4- to 5-fold increase in melatonin concentration. The risk of this interaction may be less likely to occur with estrogen products that have limited systemic absorption (e.g., vaginal, topical products).

MANAGEMENT: Caution is advised when melatonin is used concomitantly with CYP450 1A2 inhibitors. Patients should be monitored closely for adverse effects such as excessive drowsiness, headache, lethargy, dizziness, irritability, nervousness, restlessness, anxiety, abdominal pain, and dyspepsia.