What this Trial Is About

This study aims to understand how NaV1.8, a specific type of sodium channel found in peripheral nerves, contributes to different types of pain in humans. To address this, suzetrigine, a highly selective blocker of the NaV1.8 channel, is used. While current pain medications often have side effects that limit their use, NaV1.8 is a promising target for new, non-opioid pain treatments because it is primarily located in the nerves that send pain signals to the brain. This study is a randomised, placebo-controlled double-blind crossover microdosing trial. This means that very small, safe amounts of the drug are injected directly into the skin of healthy volunteers to observe its effects locally. This approach ensures the drug works only at the injection site with negligible exposure to the rest of the body. Healthy volunteers will undergo six different types of brief, controlled pain tests to see which ones are reduced by blocking NaV1.8. These tests are as follows: * Electrical stimulation: Brief electrical pulses delivered onto the skin. * Mechanical stimulation: A standardised "pin-prick" stimulation of the skin. * Chemical stimulation: An injection of fluid containing capsaicin (the active component of chilli peppers) superficially into the skin. * Heat stimulation: An injection of hot fluid superficially into the skin. * Cold stimulation: An injection of cold fluid superficially into the skin. * Acid stimulation: An injection of acidic fluid superficially into the skin. By comparing the effects of suzetrigine against a placebo and a standard local anaesthetic (lidocaine), the study will help determine which specific pain modalities critically depend on NaV1.8.

The Role of NaV1.8 in Human Pain Models