Drug Interactions between dexamethasone / moxifloxacin and thallous chloride, tl-201

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 of certain drugs may alter the myocardial uptake of thallous chloride Tl-201 and interfere with results of myocardial imaging studies. Drugs that increase or decrease coronary blood flow or potassium uptake may alter the biodistribution of thallous chloride Tl-201. Use of these drugs with thallous chloride TI-201 during imaging studies may result in a decrease in the number and size of perfusion defects, the appearance of false myocardial defects, and a decrease in myocardial localization and an increase in liver localization.

MANAGEMENT: Clinicians should be aware of possible diagnostic interference by these drugs.