Fentanyl and Isoflurane interaction
Fentanyl and Isoflurane: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Fentanyl (FENTANYL CITRATE) label · effective 2026-04-07
• Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.
Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.
Reserve concomitant prescribing of Fentanyl Citrate Injection and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate [see Warnings and Precautions (5.3) , Drug Interactions (7) ] .
Adequate facilities should be available for postoperative monitoring and ventilation of patients administered anesthetic doses of Fentanyl Citrate Injection.
Risks from Concomitant Use with Benzodiazepines or Other Central Nervous System Depressants When benzodiazepines or other CNS depressants are used with Fentanyl Citrate Injection, pulmonary arterial pressure may be decreased.
From the Isoflurane (FORANE) label · effective 2024-12-09
• Concomitant use of N 2 O and/or opioids reduces the MAC of FORANE.
Opioids Opioids decrease the Minimum Alveolar Concentration (MAC) of FORANE.
In general, anesthetic concentrations of FORANE at equilibrium reduce the ED 95 of succinylcholine, atracurium, pancuronium, rocuronium and vecuronium by approximately 25 to 40% or more compared to N 2 O/opioid anesthesia.
Opioids such as fentanyl and its analogues, when combined with FORANE, may lead to a synergistic fall in blood pressure and respiratory rate.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.