WARNING: SERIOUS AND LIFE-THREATENING RISKS FROM USE OF METHADONE HYDROCHLORIDE INJECTION Addiction, Abuse, and Misuse Because the use of Methadone Hydrochloride Injection exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death, assess each patient’s risk prior to prescribing and reassess all patients regularly for the development of these behaviors and conditions (see WARNINGS ). Life-Threatening Respiratory Depression Serious, life-threatening, or fatal respiratory depression may occur with use of Methadone Hydrochloride Injection, especially during initiation or following a dosage increase. To reduce the risk of respiratory depression, proper dosing and titration of Methadone Hydrochloride Injection are essential (see WARNINGS ). Neonatal Opioid Withdrawal Syndrome (NOWS) Neonatal opioid withdrawal syndrome (NOWS) is an expected and treatable outcome of use of Methadone Hydrochloride Injection during pregnancy. NOWS may be life-threatening if not recognized and treated in the neonate. The balance between the risks of NOWS and the benefits of maternal Methadone Hydrochloride Injection use may differ based on the risks associated with the mother’s underlying condition, pain, or addiction. Advise the patient of the risk of NOWS so that appropriate planning for management of the neonate can occur (see WARNINGS ). Managing Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of Methadone Hydrochloride Injection and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate (see WARNINGS , PRECAUTIONS ). Life-Threatening QT Prolongation QT interval prolongation and serious arrhythmia (torsades de pointes) have occurred during treatment with methadone. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Closely monitor patients with risk factors for development of prolonged QT interval, a history of cardiac conduction abnormalities, and those taking medications affecting cardiac conduction for changes in cardiac rhythm during initiation and titration of Methadone Hydrochloride Injection (see WARNINGS ). Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The concomitant use of Methadone Hydrochloride Injection with all cytochrome P450 3A4, 2B6, 2C19, 2C9 or 2D6 inhibitors may result in an increase in methadone plasma concentrations, which could cause potentially fatal respiratory depression. In addition, discontinuation of concomitantly used cytochrome P450 3A4 2B6, 2C19, or 2C9 inducers may also result in an increa...
Adult Dosing
General dosing
Important General Information Consider the following important factors that differentiate methadone from other opioids: • The peak respiratory depressant effect of methadone occurs later and persists longer than its peak pharmacologic effect. • A high degree of opioid tolerance does not eliminate the possibility of methadone overdose, iatrogenic or otherwise. Deaths have been reported during conversion to methadone from chronic, high-dose treatment with other opioid agonists and during initiation of methadone treatment of addiction in subjects previously abusing high doses of other opioid agonists. • There is high interpatient variability in absorption, metabolism, and relative analgesic potency. Population-based conversion ratios between methadone and other opioids are not accurate when applied to individuals. • With repeated dosing, methadone is retained in the liver and then slowly released, prolonging the duration of potential toxicity. • Steady-state plasma concentrations are not attained until 3 to 5 days after initiation of dosing . • Methadone has a narrow therapeutic index, especially when combined with other drugs.
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