 - PK study Blood samples 0.2 mL per sample will be taken in 30 newborn infants at t0, 1, 4, 12, 36, 60 h group 1 after the administration of one dose of methadone, and in 30 newborn infants at t0, 2, 8, 24, 48, 72 hr group 2 after the administration of methadone. A total of 1.5 ml of blood will be collected from each subject 