Last month, I highlighted how chronic pain is caused by actual physiological changes, especially affecting neurotransmitters in the central and peripheral nervous systems. Medications used to treat pain can affect the chemical balance at many of these sites.
While a review of all the treatment options for pain would fill this entire journal, I hope to highlight a few pearls across the broad spectrum of options.
Many commonly used therapeutic agents were originally released with other primary indications. Those that are marketed specifically for pain are often proven with clinical trials on diabetic neuropathy and zoster pain. Our much broader use for bread-and-butter ailments — arthritis, back and neck pain, sciatica, headaches, fibromyalgia and other myofascial pain — has data behind it, but can often be considered “off label,” in many instances, though such use is widespread.
When using common OTC analgesics in people with headaches, think about rebound headaches, even with acetaminophen. Try to get patients to only take them on average a third of the time and they won’t get this problem. The same applies to the triptan meds, which can also lead to rebound with overuse.
Antidepressants for pain
Tricyclics are useful for many chronic pain syndromes. Even low doses can have profound effects on some patients. Start with lower doses and build up gradually to minimize adverse effects. Give the bulk of the dose at night to minimize daytime sedation, though an additional morning dose can be added. This actually applies to many of the other pain modulating drugs, which often have some sedative side effects. Typically use amitriptyline, doxepin, or nortriptyline and desipramine, which are less sedating for some individuals. Usual doses can range from 10-50 mg at bedtime and an optional similar or smaller dose in the morning. Higher doses can be used, but there will be more side effects.
The related drug trazodone can be used similarly, starting with doses of 25-50 mg hs and potentially increasing up to 200 mg daily, again with most of the medication at bedtime. This is especially useful for fibromyalgia patients.
Duloxetine has recently been released in our country, though it’s been available elsewhere for some time. As an SNRI it can have antidepressant and independent pain modulating effects. Venlafaxine also has such actions. Duloxetine can be prescribed up to 60/120 mg daily and venlafaxine usually up to 300 mg a day.
Muscle relaxants and neuropathic meds
If standard muscle relaxants such as cyclobenzaprine and methocarbamol don’t help, consider baclofen and tizanidine. Baclofen can be started at 10 mg hs or bid and gradually increased up to 20 mg qid. Tizanidine has some weak α-2 adrenergic effects (similar to clonidine which is also known to have some pain modulating effects). For practical purposes, start with 2-4 mg bid gradually increasing up to 8 mg tid, if necessary.
For neuropathic pain the antiepileptic class of drugs can have especially useful therapeutic properties. Years ago we primarily used phenytoin, carbamazepine, and valproic acid. While these still serve a useful purpose the newer drugs such as gabapentin and pregabalin have fewer side effects, and may require less blood monitoring. Gabapentin can be started in the range of 100-300 mg hs or bid and then increased up to the range of 3,000 mg daily in divided doses, as long as there are no intolerable side effects. Pregabalin can be started in doses from 25-75 mg hs or bid and increased up to 600 mg daily total in 2 or 3 doses with similar caveats.
Topiramate can also be useful for neuropathic pain and be especially helpful for migraine headache prophylaxis. Usually start with 15-25 mg hs and increase to the range of 200 mg/day either all hs or split bid. Remember to watch for metabolic acidosis, which can occur at higher doses. Unlike many pain medications, which tend to have sedative and weight gain side effects, this one has a side effect of weight loss, which pleases our heavier suffering patients.
Opioids: be careful, not fearful
Opioid analgesics certainly have a role in the treatment and palliation of chronic pain states. Their common adverse events and potential for abuse and diversion are also well recognized. Many physicians may limit their use because of the negatives and thus underutilize them in appropriate cases. Pain is what these drugs were made for, so consider them, but use appropriate protocols and precautions. A significant portion of the general population may have addictive issues, and some of these will also fall into the category of legitimate pain sufferers. They can be managed with a “shorter leash.” Methadone can also be used in these individuals, primarily for its pain modulating effects.
Cannabinoids are known to have pain modulating qualities. While quite a few of our patients may be using unprescribed cannabis, which we may or may not know about, they will usually tell you if you ask. Those who are responsible could be considered for prescriptions of oral cannabinoids like nabilone or the Sativex spray.
Sleep disruption and nonrestorative sleep may be a problem associated with chronic pain syndromes and will compound the tendency to heighten pain. Many of the above drugs will have sedative side effects and improve sleep. Some patients may benefit from zopiclone 3.7-15 mg hs, or a benzodiazepine judiciously, or other nocturnal sedation.
I should emphasize that as dosage goes up, so does the tendency for side effects. Patients may get more benefit from lower doses of several drugs rather than a single agent. I tell them that if three medicines will each bring only a 10-20% improvement, cumulatively we can get them to the 50% better range.
Finally, I’d like to comment on patients who say they’ve “tried everything” and nothing works. That’s rarely the case. Often they’ve tried some meds at too low a dose and discarded them. Another therapy may have been initiated too fast, caused side effects and been jettisoned. From the categories above, there are over 25 options to choose from. Patience and a systematic approach will often lead the way to a therapy that brings real benefit.
Steve Blitzer, MD, DAAPM practices family medicine in Thornhill, ON, and has a special interest in medical rehabilitation and pain management. He is on staff at York Central Hospital, Richmond Hill, and at St. Joseph’s Health Centre in Toronto.