You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Most common side effect of phenytoin is: and explain in detail?
Side Eﬀect Of Phenytoin 

Headache
Nausea
Vomiting 
Constipation 
Dizziness
Feeling of spinning 
Drowsiness
Swelling and bleeding of the gums
Trouble in sleeping or nervousness may occur