Light-activated drugs against neuropathic pain

A team of researchers led by the Institute for Bioengineering of Catalonia (IBEC) has developed light-activated derivatives of the anti-epileptic drug carbamazepine to treat neuropathic pain. These compounds, which show analgesic effects when activated by light, can inhibit nerve signals locally and on demand. Photopharmacological treatments offer precise action at the site of application, thus reducing systemic side effects. This innovative approach involves modifying the chemical structure of a drug by adding a light-activated molecular switch, such as azobenzene. This allows the drug to be activated only when exposed to a specific colour of light, rather than in the dark. Based on these principles, IBEC has developed photoswitchable derivatives of carbamazepine, an anti-epileptic drug widely used in medicine to combat some types of neuropathic pain, such as trigeminal neuralgia. These compounds, which have an analgesic effect when activated by light, can inhibit nerve signals locally and on demand. They are activated at wavelengths corresponding to the amber colour, which allows them to pass through tissue and bone using conventional halogen lamps. Neuropathic pain is caused by lesions or diseases of the somatosensory system, such as lumbar radiculopathy (“sciatica”), diabetic neuropathy and chronic post-operative pain. The treatment of this type of pain often requires opioids, which are stronger analgesics than the usual NSAIDs – such as paracetamol and ibuprofen. However, their use is controversial due to their inconsistent efficacy, the need for high doses that can lead to tolerance and addiction, and systemic side effects such as constipation, nausea, dizziness and drowsiness. In rat models developed at the University of Cádiz, carbadiazocine has shown analgesic effect on neuropathic pain without any signs of anaesthesia, sedation or toxicity. These results demonstrate a simple and convincing treatment with non-invasive illumination.