What are the challenges when switching a patient to methadone for pain control?
There are two primary challenges:the first is the tremendous interpatient pharmacokinetic variability. The second is understanding equianalgesic potency and opioid dose-conversion tables. Q: Can you comment on the pharmacokinetics of methadone? A: The pharmacokinetic properties of methadone govern both the advantages and the difficulties of using this opioid for pain control in seriously ill patients. Methadone’s half-life is highly variable, ranging between 12 and 150 hours. In most patients, the half-life is approximately one day. In addition, irrespective of the dose or route of administration, it takes from 5 days to a week or more in some patients to reach steady-state plasma levels, so methadone does not take effect immediately. Once steady state is reached, the duration of analgesia is 6 to 12 hours. Q: What do you need to watch for? A: Since methadone’s half-life is so much longer than the duration of analgesia, there is a risk of drug accumulation which can increase the potent
