Lamotrigine-Methadone Drug Interaction

Key Interaction: Rifamycins Affect Both Drugs

Rifamycins significantly reduce lamotrigine levels through enzyme induction, requiring dose increases and therapeutic drug monitoring, according to the Infectious Diseases Society of America 1
The American College of Clinical Pharmacology recommends therapeutic drug monitoring when rifamycins are used with lamotrigine, and anticonvulsant dose increases may be required 1
Rifampin and rifapentine use may require methadone dose increases due to enhanced metabolism, as suggested by the Clinical Infectious Diseases guidelines 1
Rifabutin infrequently causes methadone withdrawal but has less pronounced effects than rifampin, according to the Clinical Infectious Diseases guidelines 1
Efavirenz and rifampin can result in opioid withdrawal due to decreased methadone levels, as reported by the Clinical Infectious Diseases guidelines 2

Lamotrigine undergoes glucuronidation rather than CYP-mediated metabolism, making direct enzyme-based interactions with methadone unlikely, as stated by the Clinical Infectious Diseases guidelines 1

Lamotrigine and methadone can generally be co-prescribed without dose adjustments for the interaction itself, according to the Clinical Infectious Diseases guidelines 1
Anticipate the need for dose increases of both lamotrigine and methadone when rifamycins are involved, as recommended by the Clinical Infectious Diseases guidelines 1
Implement therapeutic drug monitoring for lamotrigine to guide dosing adjustments when rifamycins are used, as suggested by the Clinical Infectious Diseases guidelines 1
Monitor closely for seizure breakthrough and opioid withdrawal symptoms when rifamycins are involved, according to the Clinical Infectious Diseases guidelines 1, 2

Methadone has wide interindividual variability in clinical pharmacology, and individual titration of doses is critical to avoid adverse outcomes, as reported by the Clinical Infectious Diseases guidelines 2