Neuropathic Pain Pharmacotherapy
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Direct answer
Neuropathic pain pharmacotherapy uses drugs that act on calcium channels, on serotonin and noradrenaline reuptake, or on sodium channels, rather than anti-inflammatory analgesics. First-line agents are gabapentinoids, duloxetine and amitriptyline, while carbamazepine is the drug of choice for trigeminal neuralgia. Treatment is matched to the underlying condition, and many patients need more than one agent to reach adequate relief.
What you must remember
- Gabapentin and pregabalin: Bind the alpha-2-delta subunit of voltage-gated calcium channels and are first-line for diffuse neuropathic pain and postherpetic neuralgia.
- Duloxetine: A serotonin and noradrenaline reuptake inhibitor that is first-line for painful diabetic neuropathy; nausea is common.
- Amitriptyline: An inexpensive tricyclic that is effective, but limited by sedation, anticholinergic effects and cardiac conduction risk.
- Carbamazepine: The drug of choice for trigeminal neuralgia; HLA-B*1502 testing is done before starting in people of Asian ancestry because of severe skin reaction risk.
- Topical options: Lidocaine plasters and capsaicin patches help localised postherpetic neuralgia.
- Tramadol and tapentadol: Tramadol is a second-line option and tapentadol a later-line one, both with opioid and noradrenergic actions, used when first-line drugs fail or are not tolerated.
- NSAIDs: Of limited value, because neuropathic pain arises from abnormal nerve signalling rather than inflammation.
Matching the drug to the condition
Drug choice follows the underlying condition and the character of the pain. The table gives the usual starting points, with the second-line option alongside.
| Condition | First-line | Second-line or notes |
|---|---|---|
| Painful diabetic neuropathy | Duloxetine, pregabalin or gabapentin | Amitriptyline, with caution in cardiac disease |
| Postherpetic neuralgia | Gabapentinoids or amitriptyline | Lidocaine plaster, capsaicin patch |
| Trigeminal neuralgia | Carbamazepine | Oxcarbazepine, after HLA-B*1502 check |
| Central neuropathic pain | Pregabalin or amitriptyline | Evidence is limited, so response is monitored |
Carbamazepine is the outlier because it suits paroxysmal, lancinating pain rather than constant burning pain. Renal function matters for gabapentinoids and duloxetine, so the dose is reviewed before it is increased.
Titration matters as much as the choice of drug. Gabapentinoids are started low and increased slowly to limit dizziness and somnolence, while amitriptyline is often given at night because sedation helps sleep and the drug is usually taken once daily. Patients should be told that full benefit can take several weeks, so early dose changes are avoided.
Where the exam tries to catch you
Examiners test whether you match the drug to the pain pattern and to the patient's comorbidities.
- Trap: Starting NSAIDs for burning diabetic foot pain Correct: neuropathic pain has a neural mechanism, so gabapentinoids or duloxetine are preferred over NSAIDs.
- Trap: Choosing carbamazepine for diffuse diabetic neuropathic pain Correct: carbamazepine is reserved for trigeminal neuralgia and paroxysmal pain, while diffuse pain responds better to gabapentinoids or duloxetine.
- Trap: Prescribing amitriptyline to an older patient with heart disease without review Correct: tricyclics cause sedation, anticholinergic effects and conduction problems, so an ECG and cardiac status come first.
Frequently asked questions
Which drug is the first choice for trigeminal neuralgia?
Carbamazepine is the first-line drug for trigeminal neuralgia and often gives good relief of paroxysmal facial pain. Oxcarbazepine is a common alternative with a different side-effect profile. Surgery is considered when drugs fail or are not tolerated.
Why is HLA-B*1502 testing relevant before carbamazepine?
HLA-B*1502 is strongly associated with severe carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis, especially in people of Asian ancestry. Testing before starting carbamazepine in such patients reduces the risk of this serious reaction. Carbamazepine should be avoided in those who carry the allele.
Why is duloxetine preferred for painful diabetic neuropathy?
Duloxetine is a serotonin and noradrenaline reuptake inhibitor with established benefit in painful diabetic neuropathy, and it also treats low mood. Common side effects include nausea and dizziness, and it should be avoided in severe renal impairment. It is often used alongside gabapentinoids when one agent alone is insufficient.
Can NSAIDs treat neuropathic pain?
NSAIDs are generally not effective for neuropathic pain, because the pain arises from abnormal nerve signalling rather than inflammation. They may still be useful for coexisting musculoskeletal pain. Gabapentinoids, duloxetine and tricyclic antidepressants are the standard first-line options instead.