Drug Interactions between dexamethasone / ketorolac / moxifloxacin and etrasimod

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: Coadministration of etrasimod with antineoplastic, immunosuppressive, or other immune-modulating therapies may increase the risk of unintended additive immunosuppressive effects. Etrasimod causes reversible sequestration of lymphocytes in lymphoid tissues. When administered daily for 52 weeks, etrasimod produced a mean reduction in peripheral blood lymphocyte count to 45% of baseline values, which may increase the risk of infections. Life-threatening and rare fatal infections have occurred in association with other sphingosine 1-phosphate (S1P) receptor modulators. Decreased lymphocyte counts persist during chronic daily dosing and generally return to normal within 4 to 5 weeks after stopping the medication.

MANAGEMENT: The safety and efficacy of etrasimod in combination with antineoplastic, immunosuppressive, or immune-modulating agents have not been evaluated. Because its pharmacodynamic effects may persist for up to 5 weeks after treatment discontinuation, concomitant use during and within 5 weeks following the last dose of etrasimod with antineoplastic, immunosuppressive, or immune-modulating agents should generally be avoided. If concomitant use within this period is considered necessary, patients should be monitored for infectious complications during this extended period. When switching from drugs with prolonged immune effects to etrasimod, the half-life and mode of action of these drugs must also be considered to avoid unintended additive immunosuppressive effects.

MONITOR CLOSELY: Due to the risk of bradycardia and atrioventricular (AV) block, the risk of QT prolongation and torsade de pointes arrhythmia may be increased during initiation of etrasimod treatment in patients receiving drugs that prolong the QT interval. Etrasimod may cause a transient decrease in heart rate during initiation of therapy. In the randomized placebo-controlled studies in patients with ulcerative colitis UC-1 and UC-2, following an initial dose of 2 mg on day 1, the greatest mean decrease from baseline in heart rate of 7.2 bpm occurred at hour 2 (UC-2) and hour 3 (UC-1). In studies UC-2 and UC-3, bradycardia was reported on day 1 in 2.9% of patients on etrasimod compared to none in the placebo group. On Day 2, bradycardia was reported in 1 patient (0.3%) treated with etrasimod compared to none in the placebo group. Overall, subjects who experienced bradycardia were generally asymptomatic. Few subjects experienced symptoms such as dizziness, and these symptoms resolved without intervention. Initiation of etrasimod treatment has also resulted in transient AV conduction delays. In the UC-1 study, after 2 mg of etrasimod on day 1 of treatment, first- or second-degree Mobitz type I AV blocks were observed in 0.7% of etrasimod- treated subjects compared to none in the placebo group. In studies UC-2 and UC-3, Mobitz type I AV blocks were observed in 0.8% of etrasimod-treated subjects compared to none in the placebo group. 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, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Because bradycardia and AV block are recognized risk factors for QT prolongation and torsade de pointes arrhythmia, advice from a cardiologist should be sought if treatment with etrasimod is considered in patients with significant QT prolongation (QTcF greater than 450 msec in males or 470 msec in females), patients with arrhythmias requiring treatment with Class 1a or Class III antiarrhythmic agents, or in patients on concurrent therapy with QT prolonging drugs with a known risk of torsades de pointes or drugs that slow heart rate or AV conduction. Temporary interruption of anti-arrhythmic therapy may be required prior to initiation of etrasimod, depending on the patient's resting heart rate. Some authorities state that treatment with an anti-arrhythmic agent may be initiated in patients who have been stabilized on etrasimod therapy for at least 7 consecutive days. The manufacturer's product labeling or local treatment protocols should also be consulted for additional guidance.

MONITOR: The combined use of corticosteroids and nonsteroidal anti-inflammatory drugs (NSAIDs) may increase the potential for serious gastrointestinal (GI) toxicity, including inflammation, bleeding, ulceration, and perforation. In a large, case-control study of elderly patients, those who used corticosteroids and NSAIDs concurrently had an estimated relative risk (RR) for peptic ulcer disease and GI hemorrhage of 14.6 compared to those who used neither. Corticosteroid use was associated with a doubling of the risk (estimated RR = 2.0), but the risk was confined to those who also used NSAIDs. It is possible that both categories of agents are ulcerogenic and have additive effects on the GI mucosa during coadministration. Some investigators have also suggested that the primary effect of corticosteroids in this interaction is to delay healing of erosions caused by NSAIDs rather than cause de novo ulcerations.

MANAGEMENT: Caution is advised if corticosteroids and NSAIDs are used together, especially in patients with a prior history of peptic ulcer disease or GI bleeding and in elderly and debilitated patients. During concomitant therapy, patients should be advised to take the medications with food and to immediately report signs and symptoms of GI ulceration and bleeding such as severe abdominal pain, dizziness, lightheadedness, and the appearance of black, tarry stools. The selective use of prophylactic anti-ulcer therapy (e.g., antacids, H2-antagonists) may be considered.

MONITOR: Coadministration with nonsteroidal anti-inflammatory drugs (NSAIDs) may potentiate the risk of central nervous system toxicity sometimes associated with fluoroquinolone use. The interaction has been reported most often with enoxacin. It may occur with other fluoroquinolones as well, but is poorly documented. The exact mechanism of interaction is unknown. Some investigators suggest that the piperazine ring of fluoroquinolones may inhibit the binding of gamma-aminobutyric acid (GABA) to brain receptors and that NSAIDs may synergistically add to this effect. Patients with a history of seizures may be at greater risk.

MANAGEMENT: Clinical monitoring for signs of CNS stimulation such as tremors, involuntary muscle movements, hallucinations, or seizures is recommended if fluoroquinolone antibiotics are prescribed in combination with NSAIDs.