The recommended starting dose for first time patients is one 100-mg Dilantin capsule three times a day, which may later be adjusted to suit individual requirements. The standard maintenance dosage for most adult patients is one capsule (strenght as per individual requirements), three to four times a day. The dosage may be increased to two capsules three times a day as necessary. A dosage of one 100-mg capsule daily, if proven effective, may be replaced with a 300-mg once a day dosage. For children, the recommended start up dose is 5 mg/kg/day in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily. The recommended daily maintenance dosage is usually 4 to 8 mg/kg. Children over 6 years old and adolescents may require the minimum adult dose (300 mg/day).

Dilantin should be stopped immediately if a skin rash appears. The drug should not be continued or restarted if the rash is exfoliative, purpuric or bullous rashes or if lupus erythematosus, Stevens-Johnson syndrome or toxic epidermal necrolysis symptoms appear. The medication also has inhibitory effects on insulin release which might lead to hyperglycemia. In diabetic patients, phenytoin may also raise the serum glucose level.

Like all other medications, Dilantin also has its side effects which include nystagmus, ataxia, slurred speech, decreased coordination, mental confusion, dizziness, insomnia, transient nervousness, motor twitchings, and headaches. In rare cases, phenytoin might also lead to dyskinesias, including chorea, dystonia, tremor, asterixis, nausea, vomiting, constipation, toxic hepatitis, liver damage, morbilliform rash, thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia. It is advisable to consult a doctor immediately if any of the above listed side effects get aggravated or persist over an extended period.

The prescribed Dilantin dosage regimen should be strictly adhered to and any clinical condition that might cause disruption in the regimen should be immediately intimated to the doctor. It is advisable to seeking medical advice prior to using other drugs or alcoholic beverages while on this medication. Dilantin might also cause development of gingival hyperplasia and related complications. Hence it is advisable to maintain good dental hygiene during therapy. Never use capsules which are discolored. The above information may also be applied to the following medications: Ethotoin, Fosphenytoin, Mephenytoin, Phenytoin. Phenytoin is also commonly known as diphenylhydantoin.