MoA
Phenytoin inhibits the voltage gated Na+ ion channels, leading to decreased depolarisation and inhibitory effects.
This is not a first line drug due to the many side effects and drug interactions
Side effects
- Jerking movements of the eyes
- Decreased coordination
- Shaking of the hands
- Slowed thinking and movement
- Memory problems
- Slurred speech
- Poor concentration
Drug interactions
Phenytoin is an inducer of CYP3A4. This means it increases production of CYP3A4 enzymes which means higher action of this enzyme. 40% of drugs are metabolised by CYP3A4 and so taking this drug will lead to increased plasma levels of many drugs.