Chronic Pain at the Pharmacy: Methadone Initiation for CRPS and Comorbidities

The Patient

Patient Bob* called our pharmacy inquiring about a new prescription for methadone that he was placed on by his pain management physician. He informed me that he does not know too much about this drug and wants to know more details about this therapy. He has complex regional pain syndrome (CRPS).

• simvastatin 40 mg daily (cholesterol)
• multivitamin 1 tablet daily
• atenolol 100 mg daily (hypertension)
• cyclobenzaprine10 mg 3 times daily as needed (muscle spasms)
• ibuprofen 200 mg 1 tablet every 4 to 6 hours (as needed for pain)
• acetaminophen 500 mg 1 tablet every 4 to 6 hours (as needed for pain)
• methadone 5 mg twice daily (pain, new medication)
• morphine 2 mg every 4 to 6 hours (as needed for breakthrough pain)

Bob informed the pharmacy that, about 4 years prior, he got into a bad motor vehicle accident and crushed both his left arm and leg. He developed CRPS and is in constant pain (including neuropathic discomfort) daily. He has tried oxycodone in the past, but according to him it was not effective at all for his pain. For the past year, he has just been taking his cyclobenzaprine, OTC pain relievers, and morphine for breakthrough pain. His pain management physician wants to re-start him on a prescribed pain regimen.

Methadone for Pain Management

To start off the counseling session, I informed Bob that methadone is an opioid medication that is utilized in different aspects of pain management (postprocedural, cancer, neuropathic pain). Onset of pain relief from the oral tablets is usually between 30 minutes to an hour. Duration of pain relief when first initiating is around 3 to 6 hours.¹ I informed him that once a person continues on therapy after the initial dose, the duration of analgesia is around 8 to 12 hours. The dose that this patient is currently on to start with is 5 mg twice daily.

Clinicians may take note of Palat et al’s recommendations for methadone titration strategies including:

1. Start at a low dose and increase slowly (start low and go-slow method)²
2. Dose can be increased, but not more than 5 mg every 5 to 7 days, which will depend on the response of the patient

Side Effects of Methadone and Drug Interactions

In the next portion of the counseling session, I touched upon the side effects of methadone. Core side effects associated with methadone and opioids, in general, include pruritis, nausea, constipation, sedation, confusion, and respiratory depression. Excessive sweating (diaphoresis) and flushing are also common with methadone use. I discussed with Bob that it is important that his provider monitor and continue to follow up with him regarding his methadone prescription to make sure there are not any major toxicities associated with therapy, which may be delayed for a few days if noted.³

Finally, I discussed with Bob the importance of storing this medication in a safe place away from children and pets. I also reminded him to be cautious of using other sedating medications, or drinking alcohol, which could exacerbate the side effects seen with methadone and lead to very serious issues (respiratory depression, death, etc.).

When engaging in new medication counseling with patients, it is important to hit upon the most crucial pharmacotherapy points to best optimize the session. Asking open-ended questions will open dialogue and allow for optimal patient education regarding the patient’s medication therapy. In this counseling session, the main points discussed were administration, titration, side effects, and drug/substance interactions.

*Identifying details have been altered.