- Pain on injection can be immediate or delayed (10-20s later)
- Cause remains unclear
- Possible mechanisms include:
- Direct irritant effect of phenol (particularly that in aqueous phase)
- Effect of pH or osmolarity – considered less likely as solution almost isotonic with physiological pH
- Indirect effect due to release of local inflammatory mediators such as kininogenin
Detailed discussion is given in an article by tan et al.