Jun 29, 2015
This is part two of a two part series on chronic pain.
Set realistic expectations when treating patients with chronic pain.
For the vast majority of patients, antidepressants are the first-line pharmacologic choice for the treatment of chronic pain.
Patients who present after the acute phase of a painful condition, whether it’s 1 week or 2 years from the injury, are treated the same. Treatment recommendations are evidence-based and the goal is a return to function. Methods of treating chronic nerve dysfunction include exercise, physical therapy, tolerance of discomfort, yoga, meditation, and the pharmacology of the pain agents. If present, comorbid anxiety, depression, and substance abuse are all addressed.
When patients are in the chronic phase of pain, we want to move away as quickly as possible from the opioids, muscle relaxants, and the belief that the pain will ever completely go away. Patients benefit immensely from starting the rehabilitation of chronic pain early, by employing non-pharmacologic methods and setting realistic expectations. When they present several years into a painful condition, treatment recommendations are the same, but the process is much harder and slower.
Specific pharmacologic therapies for chronically painful conditions.
Almost every antidepressant that works on serotonin and norepinephrine has some benefit for neuropathic pain.
SNRI's (duloxetine, venlafaxine) are the initial drugs of choice, because they work well for pain and have the added benefit of treating comorbid depression or anxiety. Duloxetine has a formal indication for the treatment of diabetic neuropathy and is the primary neuropathic pain antidepressant. These agents tend to treat depression and anxiety lower doses, but much higher doses are needed to get neuropathic pain benefit.
Tricyclic antidepressants (amitriptyline, imipramine, nortriptyline) are effective, but can be hard to tolerate. They’re anticholinergic and have alpha blocking properties which can cause orthostasis and a prolonged QT interval. Certain tricyclics have a formal indication for the use in migraines, fibromyalgia, and irritable bowel syndrome. TCA's have immediate pain benefit at lower doses, but in order to get the mood and anxiety benefits, doses usually need to be much higher. It’s the opposite of the general dosing rule for SNRI's.
The anti-pain benefit of antidepressants is independent of the treatment of depression.
Dr. Hersevoort starts most patients with neuropathic pain on antidepressants, because the vast majority are also depressed.
Virtually all have a benefit for neuropathic pain.
Like the antidepressants, there are certain agents which are specifically recommended for neuropathic pain conditions.
Carbamazepine (Tegretol) is the drug of choice for trigeminal neuralgia.
Gabapentin (Neurontin) is the recommended agent for postherpetic neuralgia.
Pregabalin (Lyrica) is formally indicated for fibromyalgia.
These agents can be combined with antidepressants, as they have a different mechanism of action.
These are not recommended for long-term, chronic pain treatment. They may have synergy with improving the analgesic response in the somatic, acute phase of pain.
If used, clonazepam is the best choice. It has the right length of action, is not tremendously dependency forming, and is easily metabolized.
The combination of benzodiazepines and opioids (particularly methadone) can be lethal.
These benefit patients primarily by making them feel more relaxed and mellow; they don’t truly “relax” the muscles.
Like opiates, their use is specific and limited to acute management of real muscle spasm or muscle injury. Data tells us that they have limited efficacy in chronic pain.
Lidoderm patches can be good adjuncts for some patients. They have a combination of neurologic benefit and placebo effect.
This centrally-acting alpha agonist appears to work for just about anything: opiates, alcohol craving, ADHD, tics.
There is a new body of research that it helps for complex regional pain syndrome, or reflex sympathetic dystrophy.
Like antidepressants and anticonvulsants, antiarrhythmics block sodium and calcium channels and in addition to blocking firing of myocardial cells, they also seem to block the firing of damaged nerves.
Intravenous lidocaine has shown benefit in some neuropathic pain conditions.
How should patients who are currently taking massive doses of prescribed opiates for chronic pain be managed when they present reporting acute pain? These patients need to be treated by a pain management specialist who can get the patient on a treatment program that incorporates non-pharmacologic therapy as well as the slow but consistent tapering of opiate drug therapy.