Drug Interactions between moxifloxacin / triamcinolone and toremifene

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.

GENERALLY AVOID: Toremifene has the potential to prolong the QT interval of the electrocardiogram in some patients. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. The effect on the QT interval is dose- and concentration-dependent. In a placebo-controlled, parallel-design clinical trial, the mean QTc interval prolongation was 21 to 26 ms with 80 mg toremifene, and the 20 mg dose also affected the QTc interval. Abnormal new U waves were observed in 4.3% of subjects with the 80 mg dose. There are no data available for the therapeutic 60 mg dose. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, women and elderly patients may be more susceptible to the QT prolonging effects of drugs.

MANAGEMENT: Coadministration of toremifene with other drugs that can prolong the QT interval should generally be avoided. If treatment with other QT-prolonging drugs is required, interruption of toremifene therapy should be considered. Caution and clinical monitoring are recommended if concomitant use is unavoidable. In patients at increased risk, electrocardiograms (ECGs) are recommended at baseline and as clinically indicated. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.