Methadone is an effective analgesic but is seldom prescribed for pain. What do you know about its properties, pitfalls, and potential?
Although methadone is considered to be at least equal to the other opioid analgesics in terms of efficacy and has pharmacologic characteristics that separate it from these other medications, misconceptions and concerns about the drug may limit its use. The following questions regard the use of methadone as an analgesic.
1. Methadone can only be prescribed as an analgesic for outpatients by an accredited methadone treatment program.
Answer: B. False
With a few rare exceptions, accreditation as a methadone treatment facility is required to dispense methadone for the treatment of opioid addiction. When prescribed as an analgesic, however, the requirements are the same as for all the other DEA Schedule II opioid analgesics. It is therefore important to document clearly in patients' records the purpose of the methadone.
2. The best schedule for starting methadone is:
A. One dose q24h
B. One dose q12h
C. One dose q8h
Answer: C. One dose q8h
Although methadone has a long half life (15-60 hours with an average of 30 hours) which is why it only needs to be taken q24h for the treatment of opioid addiction, its analgesic effect is much shorter (4-8h) and therefore when used to treat pain it needs to be taken more frequently-on a q8h or q6h schedule.
3. How many days does it usually take before methadone begins to exert a marked analgesic effect?
Answer: D. Five days
It usually takes at least 3-5 times the half-life of the drug before a steady state is attained and the effects of the drug observed.
4. How does methadone differ from most of the other long-acting/extended release (LA/ER) opioid analgesics?
A. In addition to being an opioid receptor agonist, it is also an NMDA receptor antagonist.
B. It has a higher potential for abuse and addiction than other opioid analgesics.
C. Although it is a long-acting medication, it cannot be manipulated so that the all the medication will be released immediately.
D. A and C.
E. B and C
Answer: D. A and C
Methadone and levorphanol are unique in that they are both µ-opioid receptor antagonists and NMDA receptor antagonists. Both of these drugs are pharmacologically long-acting as opposed to the other LA/ER opioids (eg, LA/ER oxycodone) which are formulated to be long-acting. Thus, the pharmacology of methadone is not effected by route of administration so it is essentially the same whether taken orally or injected IV or IM.
5. Which of the following is often a factor that limits the use of methadone as an analgesic?
A. Limited accessibility related to the fact that non-hospital outpatient pharmacies often do not carry it
C. Patient concerns that a prescription for methadone will cause them to be considered drug addicts
D. A and B
E. B and C
Answer: D. A and B
Methadone is inexpensive. However, because many physicians do not prescribe it, many outpatient pharmacies outside of hospitals do not stock it. If you are considering prescribing it, it is important to make sure that the patient has access to a pharmacy that stocks it.
Because methadone is traditionally associated with the treatment of opioid addiction, many patients may believe this is all it is used for. Therefore, if you prescribe it as analgesic, it is important to explain this to them.
6. With regard to dosing of methadone as as an analgesic, which of the following is the most accurate?
A. Doses required to attain analgesia are usually smaller than those required for methadone maintenance for opioid addiction.
B. The dose required for analgesia is usually about the same as that used for methadone maintenance.
C. The dose required for analgesia is usually higher than required for methadone maintenance.
Answer: A. Doses required to attain analgesia are usually smaller than those required for methadone maintenance for opioid addiction.
Although many patients in methadone maintenance programs require at least 80 to 100 mg of methadone per day or more, rarely do patients require more than 40-60 mg qd for analgesia.
7. Of the following tests, which would be considered most important to perform before initiating methadone therapy?
B. Urine analysis
Answer: A. Electrocardiogram
Because methadone can cause QTc interval prolongation, patients with a history of cardiac disease should have had an ECG within the previous three months prior to initiation of treatment. Even for patients without any history of cardiac disease, an ECG should be considered.
Whether urine analysis is important to obtain before starting patients on opioids for an extended period is controversial. As of yet there is no evidence that they reduce the risk for opioid abuse.
Methadone doesn't affect the CBC.
Source: Chou R, Cruciani RA, Fiellin DA, et al. Methadone safety: A clinical practice guideline from the American Pain Society and College on Problems of Drug Dependence, in collaboration with the Heart Rhythm Society.J Pain. 2014;15:321-337