The mean oral methadone dosage is reported to be 60-100 mg per day (Vazquez 2006).

We measured methadone oral dosages in three methadone clinics in Paris (Espace Murger, Marmottan, Horizons). The number of patients evaluated was 197. They were all at the steady state of methadone treatment. The influence of sex, center, age and retention in the program on prescribed oral dosage was tested with khi2 and spearman tests.

The mean dosage was 52 mg/d (+/- 28). The mean retention in the methadone program was more than three years. The dose range was [5-130]. The dosage was not different according to sex (p= 0,388), retention (p = 0,744), and age (p = 0,144). But the dosages were statistically different according to the center: 60 mg/d in Horizons (N = 37), 54 mg/d in Murger (N = 104), and 44 mg/d in Marmottan (N = 56) (p = 0,022).

This study confirms the great variability of methadone oral dosages in France, with a center-effect. Dosages that were found are still lower than what is found in other countries [5-350 mg/j] (Eap 2000). Other variability factors are to be considered: clinical, pharmacokinetic and pharmaco-dynamic factors.

[1]. Vazquez V, Gury C, Laqueille X. Méthadone : de la pharmacocinétique à la pharmacologie clinique. L'Encéphale 2006 ; 32 : 478-86

[2]. Eap CP, Bourquin M, Martin JL, et al. Plasma concentrations of the enantiomers of methadone and therapeutic response in methadone maintenance treatment. Drug and Alcohol Dependence 2000 :61,47–54