Reason for Partially Effective LA

Question: Why does LA not function efficiently in an inflamed environment?  

Answer: The molecule of local anaesthetic agent enters the neural cell through myelin sheath from interstitial fluid by a simple diffusion process. Then in the acidic environment of a neural cell, it breaks itself in its components and acts on the sodium influx gate and blocks it, thus blocking the generation of action potential, thus blocking signal conduction along the nerve cell membrane. The local anaesthesia cannot act on sodium influx gates from outside the nerve cell. It must enter the nerve cell.   

So, what happens when the area surrounding the nerve gets inflamed?  

I shall tell you the event that occurs. 

Once the tissue is inflamed, the interstitial fluid becomes acidic in nature. In an acidic environment, the local anaesthetic molecule breaks down. A broken local anaesthetic molecule cannot pass through the cell membrane by a simple diffusion process and thus cannot produce its effect.  

This is the reason a local anaesthetic cannot produce its effect in an inflamed tissue or is not so effective in an inflamed area.