The International Association for the Study of Pain (IASP) defines neuropathic pain as “pain caused by primary damage or dysfunction of the nervous system”. The pathogenesis is related to central sensitization, abnormal excitation of neurons and excessive release of neurotransmitters induced by central nervous system injury or disease. Depending on the site of primary damage or dysfunction of the nervous system, it can be divided into peripheral neuropathic pain and central neuropathic pain. Postherpetic neuralgia (PHN) and diabetic peripheral neuralgia (DPN) are the most representative peripheral neuropathic pains, while central neuropathic pain is commonly post-stroke neuralgia. At present, the main drugs for the treatment of neuropathic pain are tricyclic antidepressants, antiepileptics, local anesthetics, and opioid analgesics. (1) TCAs (tricyclic antidepressants) TCAs are commonly promethazine, chlorpromethazine, amitriptyline, and doxepin, which have better antidepressant effects than MAOI, and are monoamine reuptake inhibitors that can inhibit 5-HT and NA, and are suitable for all kinds of depression. In addition, there are cardiovascular adverse effects, such as arrhythmias, conduction block, upright hypotension, and cardiac insufficiency, especially in the elderly. 2010 National Institute for Health and Clinical Excellence (NICE) guidelines recommend amitriptyline as the first-line agent for diabetic peripheral neuralgia. The 2007 Canadian Pain Society guidelines recommend tricyclic antidepressants as one of the first-line drugs for the treatment of chronic neuropathic pain. (2) Selective 5-HT and NA reuptake inhibitors (SNRIs) SNRIs can block both 5-HT and NA reuptake, i.e. double blocking effect. The representative drugs are venlafaxine and duloxetine, the latter of which is not available in China. The pharmacological mechanism of venlafaxine is to inhibit presynaptic membrane 52HT and NA reuptake, enhance central 5-HT and NA neurotransmitter function, and exert antidepressant effects. It has little affinity for histamine, choline and adrenergic receptors, and has mild adverse effects. Its slow-release oral formulation is well absorbed, with plasma t1/2 of 15h and bioavailability of 96%-105%. Clinical studies have shown that this drug is effective and safe in the treatment of depression, and facilitates long-term maintenance treatment of patients. The effect of venlafaxine in reducing pain is similar to that of TCA, and the adverse effects are less than those of TCA, so venlafaxine can be used when patients cannot tolerate TCA-like side effects. Duloxetine has been approved by FDA in September 2004 for the treatment of diabetic peripheral neuropathy. 2010 UK NICE guideline recommends duloxetine as the first-line drug for diabetic peripheral neuralgia. The main mechanisms of antiepileptic drugs in the treatment of neuropathic pain include: reducing the inward flow of Na+ and Ca2+ to neurons, directly and indirectly enhancing the inhibitory effect of GABA, and reducing the excitatory neurotransmitter glutamate activity by depleting the stores of the neurotransmitter glutamate or blocking the NMDA receptor site of glutamate. (1) Carbamazepine Carbamazepine inhibits neuronal hyperexcitability by blocking Na+ channels and voltage-dependent Ca2+, and is effective in diabetic neuropathy, postherpetic neuralgia, and spinal tuberculosis pain. The 2007 Canadian Pain Society guidelines recommend carbamazepine only for the treatment of trigeminal neuralgia (primary) and not for the treatment of other neuropathic pain. (2) Gabapentin Gabapentin is a new antiepileptic drug, which is a derivative of γ-aminobutyric acid (GABA), and its pharmacological effects may include: (1) antagonism of N-methyl-D aspartate; (2) antagonism of calcium channels in the central nervous system and inhibition of abnormal firing of peripheral nerves; (3) increased inhibition of central nervous system-aminobutyric acid-mediated afferent pathways. Gabapentin is well tolerated and has very few serious adverse effects. The most common adverse effects include drowsiness, dizziness, ataxia, and fatigue. 2007 Canadian Pain Society guidelines recommend gabapentin as one of the first-line drugs for the treatment of chronic neuropathic pain. (3) Pregabalin Pregabalin is similar in structure and action to gabapentin, and is also a derivative of γ-aminobutyric acid (GABA), which inhibits the α2-delta subunit of the voltage-dependent calcium channel in the CNS (pregabalin binds to it more than six times more effectively than gabapentin), reduces calcium inward flow, inhibits neurohypersensitization, and consequently reduces glutamate, noradrenaline, and substance P. This reduces the release of excitatory neurotransmitters such as glutamate, norepinephrine, and substance P, thereby effectively controlling neuropathic pain. Compared with gabapentin, pregabalin is effective at a starting dose of 150 mg/d and is easy to administer. Adverse effects are mild, mainly dizziness, drowsiness and peripheral edema such as ankle edema. The FDA approved indications for pregabalin are: diabetic peripheral neuralgia, post-herpetic neuralgia, adjunctive treatment of adults with partial-onset epilepsy, and fibromyalgia. 2010 UK NICE guideline recommends pregabalin as the only effective first-line drug for the treatment of both central and peripheral neuropathic pain. 2007 Canadian Pain Society guideline also recommends pregabalin as one of the first-line drugs for the treatment of chronic neuropathic pain. In 2007, the Canadian Pain Society guidelines also recommended pregabalin as one of the first-line drugs for chronic neuropathic pain. Local anesthetics have many advantages, such as fewer interactions with other drugs, fewer systemic side effects, and titration-free dosing. 5% lidocaine patches are FDA-approved for the treatment of postherpetic neuralgia. It is also effective in non-postherpetic neuralgia patients with persistent pain and abnormal pain, with the latter being more effective. The American Academy of Neurology 2004 guidelines have recommended topical lidocaine for the treatment of postherpetic neuralgia (Class A). 2010 UK NICE guidelines also recommend lidocaine as the first-line drug for postherpetic neuralgia. Opioid analgesics have strong effects and are more effective in combination with other drugs, and can be considered for patients who do not respond to other drugs. Eisenberg et al. used meta-analysis to study trials of opioids and found that short-term (<24 hours) treatment effects were inconsistent, but mid-term (8-56 days, mean 28 days) trials showed that opioids were significantly more effective than placebo for spontaneous NPP. NPP was significantly more effective than placebo. The American Academy of Neurology 2004 guidelines recommend opioid analgesics for the treatment of postherpetic neuralgia (Class A), and the 2007 Canadian Pain Society guidelines include opioid analgesics and tramadol as second-line agents for the treatment of chronic neuropathic pain. The mechanism of action of capsaicin is unknown, but it is thought to desensitize afferent sensory nerves by inhibiting the release and depletion of a neurotransmitter known to sense injury called substance P. Capsaicin may also be used to treat chronic skeletal pain. Capsaicin may alleviate chronic skeletal muscle or pathological pain, but is less effective and may be used as an adjunctive treatment. Topical capsaicin for neuropathic pain is generally used as a third-line agent in international guidelines. Newer antiepileptic drugs such as lamotrigine and topiramate are also used as third-line agents, including amantadine, a noncompetitive NMDA receptor antagonist that may be effective in cancer patients with NPP. amantadine was shown to reduce diabetic peripheral neuralgia after one week of intravenous amantadine in a randomized, double-blind controlled trial by Amin et al. and was sustained. NSAIDs, as traditional analgesic drugs, are widely used in various pain treatments, and patients with neuropathic pain are no exception. Sixth, the combination of treatment foreign literature reported that about 70% of patients to a single therapy effective, the remaining 30% of patients pain relief is not enough, in this case, the need for a combination of drugs. Some patients are clinically effective for a certain treatment, but may be limited due to dose-related side effects, for these patients can be used in combination to relieve pain without worrying about dose-related side effects. However, there is little information available on the use of combinations, and drug selection is entirely empirical. There is good evidence that gabapentin combined with morphine may be effective in refractory neuropathic pain where conventional treatment has failed. Gabapentin combined with morphine dose-dependently inhibits dorsal horn neuronal responses in rats with ligated spinal nerves, and this inhibition is stronger than morphine or gabapentin alone. Please consult your physician for specific medications.