Methadone Interaction With Other Drugs
When a person takes medication there is always a risk to how they new medication will interact with other drugs. In the case of methadone, there are more than 100 substances that can interact in some fashion to affect a patient’s response. These substances include prescription medications, illicit drugs, and even “over the counter” (OTC) products which would seem to be benign. This is a significant issue, because many individuals in methadone maintenance treatment (MMT) have co-occurring physical and/or mental disorders requiring multiple medications.
Drugs are broken down, or metabolized, by chemical reactions into molecules that can more easily be eliminated. One of the primary ways in which the body metabolizes drugs involves proteins. Proteins facilitate these chemical reactions, allowing the medication to accomplish its purpose. These proteins are known as CYP450 enzymes, and there are more than 28 CYP enzymes encoded to 57 different human genes.
There are 3 different, primary ways in which substances interact with the enzyme system:
- 1) by acting as a substrate
- 2) through inhibition
- 3) through induction
A substrate is any drug metabolized by one or more CYP enzymes, an inhibitor slows the metabolism of substrate drugs, and an inducer boosts the metabolism of substrate drugs. Inhibitors may cause an excessively high drug level and related toxic effects, while and inducer may cause a lower than expected level of the substrate drug.
For a detailed list of medications, illicit drugs and other substances that may cause a drug interaction with methadone, see Addiction Treatment Forum, 3rd Edition, November 2005 Revision/Update by Stewart B. Leavitt, Ph.D. (PDF)
