Imagine a painkiller that only switches on in injured tissue, leaving the rest of the body unaffected. That is the idea behind a new class of pH-dependent drugs that interfere with nerve signals to the brain and spinal cord – but only where the tissue is slightly acidic due to injury.
Normal tissue has a pH of around 7.4, but this drops to around 7.0 in injured tissue, largely because the blood supply is disrupted, resulting in the accumulation of waste products such as carbon dioxide and a switch to anaerobic respiration, which produces lactic acid.
The new drugs act by…
