RESUMEN
CONTEXT: Elaboration of oral liquid formulations is the best alternative when no marketed forms are available for pediatrics. OBJECTIVE: The development, characterization and stability evaluation of methadone (MI, MII, MIII) and phenobarbital (PI, PII) can be used for the treatment of neonatal abstinence syndrome (NAS). MATERIAL AND METHODS: A standard operating procedure was established and parameters such as appearance, pH, rheological behavior and drug content were evaluated at three temperatures for 90 days. RESULTS AND DISCUSSION: Changes in color of phenobarbital made necessary the storage below 25 °C. pH did not change in methadone solutions and was able to maintain phenobarbital solubilized. Degradation data at 4 °C fitted to Plateau equation followed by one phase decay. MI was stable for 60 days at the three temperatures; MII for 90 days at 4 and 25 °C and 60 days at 40 °C; MIII for 60 days at 4 °C, 15 days at 25 °C and 7 days at 4 °C. PI was stable for 60 days at 4 °C and 30 days at 25 °C. PII was stable for 7 days at 4 and 25 °C. All solutions met microbial specifications. CONCLUSION: A correct dosage for the treatment of NAS was guaranteed.