1,3 Other pharmacokinetic considerations for methadone include its absorption, distribution, metabolism, and elimination.Ĭonversions from other opioids to methadone are non-linear, and patients who are stable on a dose of another opioid often show incomplete tolerance to methadone. 1-4 The half-life of methadone typically is between 15 and 60 hours, although it has been reported to be as long as 120 hours in some patients.
Perhaps the most challenging aspect of methadone’s pharmacokinetics is its long and variable half-life. However, an understanding of these pharmacokinetics can allow practitioners to use methadone safely and take advantage of its therapeutic potential. Methadone’s complex pharmacokinetics require close attention to detail to allow appropriate patient selection, initial dosing and titration, and monitoring. These characteristics enable methadone to be used in cases in which other opioids fail, whether due to patient allergy and intolerance, or lack of efficacy. On the other hand, methadone’s low cost and unique mechanism of action make it more accessible, and potentially more beneficial, to patients. In addition, it carries risks, such as the potential for prolongation of the QTc interval, that are not associated with other opioids. Methadone’s pharmacokinetics and mechanism of action are more complex than those of other opioids. While methadone can be more challenging than other opioids to use clinically, it also is potentially more helpful. Methadone’s unique pharmacokinetic and pharmacodynamic properties render it distinguishable from other opioids.