Is it safe to take methadone with other medications?

Many drugs are digested (metabolized) by chemicals in the liver called enzymes. Methadone is metabolized this way and other drugs broken-down by the same liver enzymes may interfere with methadone and change its effects – this is called a “drug interaction.”

A drug interaction occurs when the amount or action of a drug in the body is altered – usually increased or decreased – by the presence of another drug or multiple drugs. During clinical use spanning more than 40 years, oral methadone has proven to be a well-tolerated medication with minimal adverse reactions when prescribed in appropriate doses and taken daily as a component of methadone maintenance treatment. However, there are potential methadone-drug interactions – involving prescribed medications, illicit drugs, OTC products, and other substances – which sometimes can be difficult to predict, may be potentially harmful, and/or can lead to treatment failures.

Methadone works best when administered in adequate therapeutic doses. However, given the individual variability in methadone absorption and metabolism, it becomes difficult to accurately predict the effects of drug combinations in any one patient, or how methadone dosing may need adjustment. Several points might be kept in mind:

• Just because certain drugs can interact does not mean that they will, or indicate to what extent.
• If a patient is responding unexpectedly or unfavorably to methadone – with signs/symptoms of under- or overmedication – a search for potentially interacting substances would be appropriate. Taking a comprehensive history from the patient can be important in this search.
• When an interaction is suspected, adjustments of medication dosages with followup monitoring, substitutions of non-interacting agents, or other therapeutic modifications might be made.
• In many cases, the daily dose of methadone may need to be either increased or decreased, depending on the interaction.

Also, it is always best for MMT patients to inform their healthcare providers that they are taking methadone and to express concern about possible interactions with any prescribed medications. MMT clinic staff should become familiar with drugs or drug combinations that may affect methadone so they can advise these outside providers