Drug Interaction Report

MONITOR CLOSELY: The use of droperidol has been associated with QT interval prolongation, torsade de pointes and other serious arrhythmias, and sudden death. The concurrent administration of agents that can produce bradycardia, a known risk factor for QT interval prolongation, such as benzodiazepines and opiates, particularly intravenous opiates, may increase the risk of QT interval prolongation. In addition, hypotensive effects and central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking droperidol with benzodiazepines or opiates, especially in elderly or debilitated patients.

MANAGEMENT: Extreme caution and close monitoring are recommended if droperidol must be administered concomitantly with other bradycardic drugs. The dosage of droperidol should be individualized and titrated to the desired effect. Routine vital sign and ECG monitoring is recommended. When droperidol is used in combination with benzodiazepines or opiates, patients should be monitored for potentially excessive or prolonged CNS or respiratory depression as well as severe hypotension. 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 doctor if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR CLOSELY: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of fentanyl, which is primarily metabolized by the isoenzyme. Increased fentanyl concentrations could increase or prolong adverse drug effects and may cause potentially fatal respiratory depression. Conversely, discontinuation of a CYP450 3A4 inhibitor could decrease fentanyl plasma concentrations, decrease opioid efficacy, and possibly even lead to a withdrawal syndrome in patients who had developed physical dependence to fentanyl. In eleven healthy volunteers, coadministration of the potent inhibitor ritonavir (200 mg orally three times a day on day 1; 300 mg three times a day on day 2; one morning dose of 300 mg on day 3) and intravenous fentanyl (5 mcg/kg two hours after the afternoon dose of ritonavir on day 2) resulted in a 174% increase in fentanyl systemic exposure (AUC) and a 67% decrease in fentanyl clearance compared to administration of fentanyl alone (with placebo). No other formulations of fentanyl such as patches or buccal tablets were studied.

MANAGEMENT: Patients receiving fentanyl with potent or moderate CYP450 3A4 inhibitors should be carefully monitored, and dosage adjustments made accordingly as needed. This is particularly important when an inhibitor is added after a stable dose of fentanyl has been achieved. Some authorities recommend avoiding concomitant use of fentanyl during and for 2 weeks after treatment with itraconazole. Patients and/or their caregivers should be advised to seek medical attention if potential signs and symptoms of toxicity occur, such as dizziness, confusion, fainting, extreme sedation, unresponsiveness, bradycardia, slow or difficult breathing, and shortness of breath. When discontinuing CYP450 3A4 inhibitors, monitor patients closely at frequent intervals and consider increasing the opioid dosage if needed to maintain adequate analgesia or if symptoms of opioid withdrawal occur. Patients treated with transdermal formulations of fentanyl should be cautioned that drug interactions and drug effects may be observed for a prolonged period beyond removal of the patch, as significant amounts of fentanyl are absorbed from the skin for 17 hours or more after the patch is removed.

MONITOR: Coadministration with berotralstat may increase the plasma concentrations and effects of drugs that are substrates of CYP450 3A4 and/or 2D6. The mechanism is decreased clearance due to inhibition of CYP450 3A4 and 2D6 activity by berotralstat. Berotralstat is considered a moderate inhibitor of CYP450 3A4 and 2D6. In drug interaction studies, berotralstat reportedly increased the peak plasma concentration (Cmax) and systemic exposure (AUC) of the sensitive CYP450 3A4 substrate midazolam by approximately 1.5-fold and 2.25-fold, respectively, and the CYP450 3A4 substrate amlodipine by approximately 1.5-fold and 1.75-fold, respectively. It increased the Cmax and AUC of the sensitive CYP450 2D6 substrate dextromethorphan by approximately 2.9-fold and 2.7-fold, respectively, and the CYP450 2D6 substrate desipramine by 1.7-fold and 1.9-fold, respectively. Clinical data are not available.

MANAGEMENT: Caution is advised when berotralstat is coadministered with drugs that are substrates of CYP450 3A4 and/or 2D6, particularly those with a narrow therapeutic index. Clinical and laboratory monitoring are recommended following the initiation of berotralstat, and the individual dosages of the concomitant agents adjusted as needed.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including fentanyl. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

GENERALLY AVOID: Consumption of grapefruit juice during treatment with oral transmucosal formulations of fentanyl may result in increased plasma concentrations of fentanyl, which is primarily metabolized by CYP450 3A4 isoenzyme in the liver and intestine. Certain compounds present in grapefruit are known to inhibit CYP450 3A4 and may increase the bioavailability of swallowed fentanyl (reportedly up to 75% of a dose) and/or decrease its systemic clearance. The clinical significance is unknown. In 12 healthy volunteers, consumption of 250 mL regular-strength grapefruit juice the night before and 100 mL double-strength grapefruit juice one hour before administration of oral transmucosal fentanyl citrate (600 or 800 mcg lozenge) did not significantly affect fentanyl pharmacokinetics, overall extent of fentanyl-induced miosis (miosis AUC), or subjective self-assessment of various clinical effects compared to control. However, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability. The possibility of significant interaction in some patients should be considered.

MANAGEMENT: Patients should not consume alcoholic beverages or use drug products that contain alcohol during treatment with fentanyl. Any history of alcohol or illicit drug use should be considered when prescribing fentanyl, and therapy initiated at a lower dosage if necessary. Patients should be closely monitored for signs and symptoms of sedation, respiratory depression, and hypotension. Due to a high degree of interpatient variability with respect to grapefruit juice interactions, patients treated with fentanyl should preferably avoid the consumption of grapefruit and grapefruit juice. In addition, patients receiving transdermal formulations of fentanyl should be cautioned that drug interactions and drug effects may be observed for a prolonged period beyond removal of the patch, as significant amounts of fentanyl are absorbed from the skin for 17 hours or more after the patch is removed.

MONITOR CLOSELY: The use of droperidol has been associated with QT interval prolongation, torsade de pointes and other serious arrhythmias, and sudden death. The concurrent administration of agents that can produce hypokalemia and/or hypomagnesemia (e.g., potassium-wasting diuretics, amphotericin B, cation exchange resins), drugs known to increase the QT interval (e.g., phenothiazines, tricyclic antidepressants, antiarrhythmic agents, etc.), certain other drugs (benzodiazepines, volatile anesthetics, intravenous opiates), or alcohol abuse may increase the risk of prolonged QT syndrome. In addition, central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking droperidol with certain other drugs that cause these effects, especially in elderly or debilitated patients.

MANAGEMENT: The manufacturer recommends extreme caution if droperidol must be given concomitantly with these agents. The dosage of droperidol should be individualized and titrated to the desired effect. Routine vital sign and ECG monitoring is recommended. When droperidol is used in combination with other drugs that cause CNS and/or respiratory depression, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. 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 doctor if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR: Smoking cessation may lead to elevated plasma concentrations and enhanced pharmacologic effects of drugs that are substrates of CYP450 1A2 (and possibly CYP450 1A1) and/or certain drugs with a narrow therapeutic index (e.g., flecainide, pentazocine). One proposed mechanism is related to the loss of CYP450 1A2 and 1A1 induction by polycyclic aromatic hydrocarbons in tobacco smoke; when smoking cessation agents are initiated and smoking stops, the metabolism of certain drugs may decrease leading to increased plasma concentrations. The mechanism by which smoking cessation affects narrow therapeutic index drugs that are not known substrates of CYP450 1A2 or 1A1 is unknown. The clinical significance of this interaction is unknown as clinical data are lacking.

MANAGEMENT: Until more information is available, caution is advisable if smoking cessation agents are used concomitantly with drugs that are substrates of CYP450 1A2 or 1A1 and/or those with a narrow therapeutic range. Patients receiving smoking cessation agents may require periodic dose adjustments and closer clinical and laboratory monitoring of medications that are substrates of CYP450 1A2 or 1A1.