Isoflurane and Promethazine and codeine interaction
Isoflurane and Promethazine and codeine: 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 Promethazine and codeine (Promethazine Hydrochloride and Codeine Phosphate) label · effective 2025-12-18
…PROMETHAZINE AND RESPIRATORY DEPRESSION IN CHILDREN; MEDICATION ERRORS; INTERACTIONS WITH DRUGS AFFECTING CYTOCHROME P450 ISOENZYMES; CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; NEONATAL OPIOID WITHDRAWAL SYNDROME Addiction, Abuse, and Misuse Promethazine HCl and Codeine Phosphate Oral Solution exposes patients and other users to the risks…
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.
Avoid the use of Promethazine HCl and Codeine Phosphate Oral Solution in patients taking benzodiazepines, other CNS depressants, or alcohol [ see Warnings and Precautions (5.10) , Drug Interactions (7.4) ].
( 5.9 , 7.1 , 7.2 , 7.3 ) 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.
Avoid concurrent use of Promethazine HCl and Codeine Phosphate Oral Solution with alcohol or other central nervous system depressants because additional impairment of central nervous system performance may occur [ see Warnings and Precautions (5.10) ].
From the Isoflurane (FORANE) label · effective 2024-12-09
Monitor QT interval when administering FORANE to susceptible patients (e.g., patients with congenital Long QT Syndrome or patients taking drugs that can prolong the QT interval).
• 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.
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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.