Drug Interactions between osilodrostat and Phenergan with Dextromethorphan

MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR: Coadministration with osilodrostat may increase the plasma concentrations of drugs that are metabolized by CYP450 1A2, 2C19, 2D6, and/or 3A4. Osilodrostat has been shown to be a moderate inhibitor of CYP450 1A2, a mild to borderline moderate inhibitor of CYP450 2C19, and a weak inhibitor of CYP450 2D6 and 3A4. In a pharmacokinetic study with 20 healthy volunteers using a single 50 mg dose of osilodrostat and a probe drug cocktail, osilodrostat increased the exposures to caffeine (CYP450 1A2 substrate), omeprazole (CYP450 2C19 substrate), dextromethorphan (CYP450 2D6 substrate), and midazolam (CYP450 3A4/5 substrate) by 2.5-, 1.9-, 1.5- and 1.5-fold, respectively.

MANAGEMENT: Caution is advised when osilodrostat is used concurrently with drugs that are substrates of CYP450 1A2, 2C19, 2D6 and/or 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever osilodrostat is added to or withdrawn from therapy.

MONITOR: Osilodrostat can cause dose-related prolongation of the QT interval. 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. In a thorough QT study with 86 male and female healthy volunteers, maximum mean placebo-corrected QTcF (Fridericia corrected QT interval) increased 1.73 msec following a 10 mg dose and 25.38 msec following a 150 mg dose (up to 2.5 times the maximum recommended dosage). The predicted mean placebo-corrected QTcF change from baseline at the highest recommended dosage in clinical practice (30 mg twice daily) was estimated to be 5.3 msec, based on an interpolation of the data from the thorough QT study and population pharmacokinetic analysis. Adverse reactions of QT prolongation and clinically relevant ECG findings have also been reported in clinical studies. 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: Caution is recommended if osilodrostat is used in combination with other drugs that can prolong the QT interval. An electrocardiogram (ECG) and serum electrolyte levels should be obtained prior to initiating osilodrostat therapy, with ECG repeated within one week after starting treatment and periodically thereafter. Correct hypokalemia and/or hypomagnesemia before starting treatment and as indicated during treatment, as they may be risk factors for ventricular arrhythmias. If QTc interval exceeds 480 msec at any point, temporary dose reduction, interruption, or discontinuation of osilodrostat may be necessary. Some authorities suggest that a washout period be considered when switching from other treatments of Cushing's syndrome that are also known to affect the QT interval such as ketoconazole or pasireotide. 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