HJAR Sep/Oct 2022

HEALTHCARE JOURNAL OF ARKANSAS I  SEP / OCT 2022 59 Julio Olaya, MD Pain Medicine Specialists of Arkansas neuropathy, postherpetic neuralgia, mixed neuropathic pain conditions, and phantom limb pain. Pregabalin is a GABAanalogue related to gabapentin that has also shown efficacy in neuropathic pain. Gabapentin and pregabalin are generally well tolerated and have no drug interactions but should be administered in smaller doses in patients with renal failure. The adverse side effects include dizziness, sedation, and occasionally peripheral edema. Lamotrigine blocks voltage-dependent Na+ channels and inhibits Na+ influx-me- diated release of excitatory amino acids from presynaptic neurons. In small trials, lamotrigine has shown efficacy in trigeminal neuralgia, HIV neuropathy, painful diabetic neuropathy, and central post-stroke pain at doses of over 200 mg/day. Lamotrigine is usually well tolerated. Side effects include rash, dizziness, and somnolence. Because of the rash, which in severe cases may progress to Stevens-Johnson syndrome, lamotrigine must be titrated slowly. Opioids There is amisconception that neuropathic pain responds well to opioids, there is noth- ing further from the truth. Opioids are the last option when treating neuropathic pain. Topicals Lidocaine blocks the voltage-gated so- dium channels, and topical application is thought to silence ectopic discharges on small afferent fibers. Lidocaine patches are used in the treatment of postherpetic neuralgia and in mixed peripheral focal neuropathy. Topically applied capsaicin has shown a significant effect in diabetic neuropathy and in postherpetic neuralgia. The use of capsaicin is very limited because of the in- convenience of applying the cream to the painful area four times a day. Summary Damage or injury to the nerves can cause neuropathic pain, and symptoms can range frommild to severe. Neuropathic pain commonly presents in primary care and is underdiagnosed.3,4 Diagnosis is based on characteristic symp- toms, altered sensations, and clinical history that matches a neuroanatomical or derma- tomal pattern. Less than half of patients achieve significant benefit with any single drug. Management includes making pain tolerable and maintaining emotional and physical functioning. Nonpharmacological approaches can be effective, but referral for specialist help is indicated if pain persists or remains uncontrolled. Some types of neuropathic painmay ease or resolve over time, while other types will require long-term pain management. If a medication is causing debilitating nerve pain, removal or decrease in the dose of the offending drug may be all that is needed. n REFERENCES 1 van Hecke, O.; Austin, S.K.; Khan, R.A.; et al. “Neuropathic pain in the general population: a systematic review of epidemiological stud- ies.” Pain 155, no. 4 (April 2014): 654-662. doi: 10.1016/j.pain.2013.11.013 2 Bennett, M.I.; Smith, B.H.; Torrance, N.; Lee, A.J. “Can pain can be more or less neuropath- ic? Comparison of symptom assessment tools with ratings of certainty by clinicians.” Pain 122, no. 3 (June 2006): 289-294. doi: 10.1016/j. pain.2006.02.002 3 Dieleman, J.P.; Kerklaan, J.; Huygen, F.J.; et al. “Incidence rates and treatment of neuropathic pain conditions in the general population.” Pain 137, no. 3 (July 31, 2008): 681-688. doi: 10.1016/j. pain.2008.03.002 4 Treede, R.D.; Jensen, T.S.; Campbell, J.N.; et al. “Neuropathic pain redefinition and a grading system for clinical and research purposes.” Neu- rology 70, no. 18 (April 29, 2008): 1630-5. doi: 10.1212/01.wnl.0000282763.29778.59 5 Dworkin, R.H.; Panarites, C.J.; Armstrong, E.P.; et al. “Is treatment of postherpetic neuralgia in the community consistent with evidence-based recommendations?” Pain 153, no. 4 (April 2012): 869-875. doi: 10.1016/j.pain.2012.01.015 6 Torrance, N.; Smith, B.H.; Watson, M.C.; Bennett, M.I. “Medication and treatment use in primary care patients with chronic pain of predominantly neuropathic origin.” Family Practice 24, no. 5 (October 2007): 481-485. doi: 10.1093/fampra/ cmm042 7 Torrance, N.; Ferguson, J.A.; Afolabi, E.; et al. “Neuropathic pain in the community: more un- der-treated than refractory?” Pain 154, no. 5 (May 2013): 690-9. doi: 10.1016/j.pain.2012.12.022 shrink a tumor that is pressing on a nerve. Even though it will not reverse neuropa- thy, an effective blood glucose control for diabetics to maintain acceptableA1C levels (below 7) will prevent it from getting worse. More goals include providing pain relief, maintaining functionality, and improving the quality of life. Along with treating the under- lying disease, medication is often needed to manage the neuropathic pain. First-line medications Antidepressants have a well-established beneficial effect in various neuropathic pain states. These include TCAs (e.g., amitripty- line and imipramine) and SNRI’s (duloxetine and venlafaxine), while the effect of SSRI’s is lower. When we decide to prescribe these medications, we need to take into consid- eration their potential undesirable side ef- fects, and we have to tailor the medical plan considering the different comorbidities that our patient might have. TCAs have several side effects, the most important ones being cardiac conduction disturbances, dry mouth, urine retention, sedation, dizziness, and orthostatic hypo- tension. An electrocardiogram is mandatory before onset of treatment. Anticonvulsants Anticonvulsant drugs are primarily in- troduced for the treatment of epilepsy. They have several pharmacological actions that can interfere with processes involved in neuronal hyperexcitability, either by de- creasing excitatory or increasing inhibi- tory transmission, thereby exerting a net neuronal depressant effect. Gabapentin is a structural analog to gamma-aminobutyric acid (GABA) that has no effect at GABAergic receptors but binds to the alpha2delta subunit of voltage- dependent Ca 2+ channels, therefore reduc- ing the calcium influx into cells. Gabapen- tin has shown efficacy in painful diabetic