What could be important to know about methadone: pharmacological matters
Methadone is a lipophilic drug with important tissue storage (fats, luing, ..) leading to a risk of delayed overdose during the days following initiation.
Half-life : 22 hours but vary from 4 to 190 h with inter- and intra-individual variations . Usally, half life is around 14h for the first administration and 22h at steady state.
Onset of analgesic effect: 30 to 60 minutes.
Duration of analgesic effect: 3 to 6 hours at initiation then 8 to 12 hours with repeated administration.
Metabolism by cytochrome P450, 2D6, 3A4, etc. Mutliple drug interactions (caution with new treatement introduced or stopped)
No active metabolites
Majority eliminated in the faeces no adjustment for renal insufficiency