Mechanism of Action Opioids in Neuropathic Pain

Neuropathic pain chronic pain caused by an injury, illness or trauma of the nervous system. The treatment of neuropathic pain is difficult due to its multiple etiologies and manifestations. Opioid analgesics are a mainstay of pharmacological treatment of neuropathic pain, though their use is controversial in chronic pain disorders.

What is Neuropathic Pain?

• There are several types of neuropathic pain, including postherpetic neuralgia, diabetic neuropathy, trigeminal neuralgia and HIV-and cancer-related neuropathies. Neuropathic pain is characterized by nerve damage in either the peripheral or central nervous system.

Mechanism of Action of Opioids

• Opioid analgesics bind to opioid receptors located in the central nervous system. This prevents the transmission of gamma aminobutyric acid, a neurotransmitter involved in pain conduction.

Analgesic Effect of Opioids

• The binding of opioid analgesics at opioid receptors inhibits the activation of the body’s natural pain pathways. This causes a decreased perception of and response to pain. Each opioid analgesic exhibits a distinct onset of action, duration of effect and level of analgesia based on its physical and chemical properties.

Effectiveness of Opioids in Neuropathic Pain

• The effectiveness of opioids in neuropathic pain has not been well-established through clinical trials, and their use is controversial. Several other pain management techniques are effective in treating neuropathic pain.

Safety of Opioids in Neuropathic Pain

• Opioid analgesics are likely to cause unwanted side effects, and the long-term use of opioid analgesics can lead to tolerance, dependence and addiction.