Medication-based Therapies
Opioid Use
Opioids are powerful analgesics that can provide relief from many types of pain; however, they also have drawbacks including sedation, severe constipation and/or nausea in many patients. Also, they can interact with other drug types, can actually increase sensitivity to pain (opioid-induced hyperalgesia, OIH), as well addiction or addiction relapse. A little known issue is opioids (and antidepressants like SSRIs, SNRIs, MAOI drugs, HIV medications and St. John’s Wort) can cause serotonin syndrome. Patients already on opioid pain killers are also at heightened risk of serotonin syndrome should then need emergent surgical care where drugs like fentanyl, pentazocine or meperidine are used.
While opioid medications can be useful keep in mind that “No study has ever shown that opioids eliminate chronic pain, other than in the very short term, so efforts to achieve a zero pain love with opioids will fail, while subjecting the patient to potentially intoxicating doses of the medication.”*
Starting a pain treatment program (e.g., for acute pain) with opioids can offer “excellent analgesia” (SAMHSA, p. 69) but the benefit diminishes with time. Typically about one-half of patients quit treatment after 1 1/2 years because of side effects or loss of effect. Patients who continue with opioids can expect about a 30% reduction in pain after 18 months.** The point is a comprehensive pain management program will need to explore other options not just because of opioid addiction risk, but to maintain a decent level of pain remediation to allow basic life quality. In addition, hyperalgesia has been found to result from use of methadone, buprenorphine, sufentanyl, fentanyl, morphine, and heroin or the opioids studied thus far.
Cannabinoids
Synthetic THC (Marinol) is approved in the United States for chemotherapy-induced nausea and AIDS-induced anorexia. Sativex, a mixture of THC and cannabidiol, is an oromucosal spray that spares the lungs the toxicity of drugs and smoke. It is analgesic in neuropathic pain and is approved in Canada for the pain of multiple sclerosis. Nabilone is a synthetic drug similar to THC. Its reported analgesic effects were determined to be weaker than codeine in a controlled study of neuropathic pain. Although it is reasonable to conclude that modulating the human cannabinoid system shows promise for treating pain, there is no reason to believe that inhaled smoke is an acceptable delivery mode. The consensus panel does not recommend smoked marijuana for treating pain (SAMHSA, 2011, p. 37).
SSRIs & SNRIs
There is good evidence for treating PTSD with serotonin-selective reuptake inhibitors (SSRIs) like Zoloft and sertonin-norephinephrine reuptake inhibitors (SNRIs) like Effexor. However, the only FDA-approved medications for PTSD are the SSRIs paroxetine and sertraline. The others can be used off-label but all should be supplemental to other treatments like CBT as no pharmacological treatments have met criteria for evidence-based treatment for PTSD.
The SAMHSA consensus panel recommends that clinicians treat comorbid anxiety and insomnia with antidepressants or anticonvulsants. Some antidepressants (e.g., trazodone, mirtazapine, amitriptyline, doxepin) may be useful sleep aids. Amitriptyline and doxepin do have strong anticholinergic effects and in addition to sedation can induce confusion, especially in the elderly.
Benzodiazepines
This class of drugs is almost uniformly discouraged in pain management. Side effects, especially in the elderly, are significant and include balance problems, memory impairment, and addiction risk. There are studies showing they actually increase pain and can reduce pain when benzodiazepine antagonists are administered.
Non-Opioid Analgesics
Medications developed for conditions other then pain control, but have shown benefit in pain are called adjuvant treatments. For the most part these involve anticonvulsants and antidepressants. Non-opioid analgesics include acetaminophen and the non steroidal anti-inflammatory drugs (NSAIDS) like ibuprofen and naproxen.
Non-Opioid Analgesics Compared
Acetaminophen – Addictive: No. Should normally not exceed 4 g/day; in adults with hepatic disease, the maximum dose is 2 g/day. Potentiates analgesia without potentiating respiratory and sedative side effects.
NSAIDS – Addictive: No. Are used to relieve numerous types of pain, especially bone, dental, and inflammatory, and enhance opioid analgesia. May cause gastrointestinal bleeding and renal insufficiency.
Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) – Addictive: No. Are used to relieve several nonstructural types of pain (e.g., migraine, fibromyalgia, low back pain) and probably others.
Tricyclic Antidepressants – Addictive: No. Have demonstrated efficacy in migraine prophylaxis, fibromyalgia, many neuropathic pains, vulvodynia, and functional bowel disorders. Watch for anticholinergic side effects and orthostatic hypotension (fall risk in older people).
Anticonvulsants – Addictive: No. Some have demonstrated efficacy in relieving fibromyalgia, migraine prophylaxis, and neuropathic pains.
Topical Analgesics – Addictive: No. Comprise several unrelated substances (e.g., NSAIDs, capsaicin, local anesthetics). Work locally, not systemically, and therefore usually have minimal systemic side effects.
Antipsychotics – Addictive: No. Have no demonstrated analgesic effect, except to abort migraine/cluster headache. Risks include extrapyramidal reactions and metabolic syndrome.
Muscle Relaxants – Carisoprodol (Soma) is addictive. Some others have significant abuse potential. Have not been shown to be effective beyond the acute period. Some potentiate opioids and are not recommended.
Benzodiazepines – Addictive: Yes. Not advised.
Cannabinoids – Addictive: Yes. Not advised. – adapted from SAMHSA pp. 35-36
Partial Opioid Agonists
About buprenorphine
*Substance Abuse and Mental Health Services Administration (SAMHSA). (2011) Managing Chronic Pain in Adults With or in Recovery From Substance Use Disorders. Treatment Improvement Protocol (TIP) Series 54. HHS Publication No. (SMA) 12-4671. Rockville, MD: Substance Abuse and Mental Health Services Administration.
**Kalso, E., Edwards, J. E., Moore, R. A., & McQuay, H. J. (2004). Opioids in chronic non-cancer pain: Systematic review of efficacy and safety. Pain, 112(3), 372–398.