Medications that Impact on Methadone Plasma
Concentrations
Some drugs can interact with methadone when it is bound to plasma proteins. As was mentioned above most binding of methadone to plasma proteins is non specific, and this means that many drugs with similar shapes can bind to the same area of the blood protein and knock the methadone molecule out. This can cause a much higher effective blood methadone level, which can be a problem for someone who does not have tolerance or even someone on a low dose of methadone without much of an initial tolerance. Some drugs can knock methadone away from the blood proteins that they are bound to causing a sudden release of methadone to them interact with the opiate receptor. Drugs that can do this are erythromycin, clarithromycin, Vitamin E and many of the NSAIDS (Ibuprofen and Ketoprofen). While the danger is obvious for the individual with a low tolerance these drugs can also have an effect on patients taking a blockade dose with a high tolerance by causing the release of their stored methadone (or buffer) ;and thus destabilizing them. It would probably take a few days to build up the methadone plasma to its initial level.