Most common side effect of phenytoin is:
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
Gingival hyperplasia
Dental stains
Hypertension
Gingival necrosis