Drug Interaction Report

MONITOR: Concomitant use of remdesivir with other agents that are known to induce hepatotoxicity may theoretically increase the risk of liver injury. Data from investigational use and clinical studies suggest that remdesivir may be associated with transaminase elevations. Transient treatment-emergent Grade 1 or Grade 2 elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were observed during multiple-dose Phase 1 studies in healthy volunteers. The mechanism of potential hepatotoxicity is unknown and the contribution of remdesivir is difficult to determine, as transaminase elevations have also been reported as a component of COVID-19, including in patients receiving placebo in clinical trials of remdesivir.

MANAGEMENT: Caution and increased monitoring may be required if remdesivir is given concurrently with other agents associated with liver injury. Hepatic function should be evaluated prior to starting remdesivir and during treatment as clinically appropriate. The manufacturer of remdesivir recommends considering discontinuation of remdesivir if ALT levels increase to greater than 10 times the upper limit of normal. Additionally, the manufacturer recommends discontinuing remdesivir if ALT elevation is accompanied by signs or symptoms of liver inflammation. The labeling of the other agent(s) involved should also be consulted as they may contain dose adjustment or discontinuation recommendations for those agent(s) in the event of hepatotoxicity.

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of macitentan, which is primarily metabolized by CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. The interaction has not been studied with grapefruit juice but has been reported for ketoconazole, a potent CYP450 3A4 inhibitor. In ten healthy subjects, coadministration of a single 10 mg oral dose of macitentan on day 5 of treatment with ketoconazole (400 mg daily for 24 days) resulted in an approximately 2-fold increase in macitentan systemic exposure compared to administration alone. However, the clinical significance of the interaction is unclear. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Until further information is available, patients receiving macitentan therapy should avoid the consumption of grapefruit or grapefruit juice.