Phenytoin: Price, Dosage & Where to Buy

Phenytoin is an antiepileptic medicine in the hydantoin group, used to control seizures in epilepsy, including tonic-clonic seizures. It is also used for seizures linked to brain surgery, and its extended-release capsules have specific labelled uses for these conditions. Phenytoin requires a prescription in the United Kingdom and is available as a generic medicine.

Extended phenytoin sodium capsules are used to treat tonic-clonic seizures, also called grand mal seizures. They are also used for psychomotor seizures, which are described in the label as temporal lobe seizures. Another labelled use is preventing and treating seizures that occur during or after brain surgery.

These are the seizure types and settings listed for the extended-release capsules. Treatment is tailored to the individual, with blood level monitoring sometimes needed to help guide adjustments.

Phenytoin helps control the repeated electrical signals in the brain that can cause seizures. Nerve cells pass signals through tiny channels in their outer surface. Phenytoin acts mainly on sodium channels, helping to limit rapid, repeated firing of these cells.

This can reduce the spread of abnormal electrical activity through the brain. Its action helps control seizures rather than removing their underlying cause.

The label lists oral capsules of 100 mg and extended-release oral capsules of 30 mg, 100 mg, 200 mg and 300 mg. The label lists an injection of 50 mg/mL, an oral suspension of 125 mg/5 mL and chewable oral tablets of 50 mg. The usual starting dose is 100 mg of extended phenytoin sodium capsules three times a day for adults who have not previously received treatment.

The label lists adult maintenance treatment as one capsule three to four times a day, with adjustments according to individual needs. The label lists 300 mg once daily as an option for adults whose seizures are controlled with divided daily doses of three 100 mg extended-release capsules. This once-daily option applies only to extended phenytoin sodium capsules.

Blood level checks may guide adjustments. Changes of brand or formulation need careful monitoring because absorption and drug content can differ. Oral loading treatment is reserved for a clinic or hospital where blood levels can be closely monitored.

A missed dose may reduce seizure control, so regular treatment matters. Check the medicine leaflet or ask a pharmacist for advice on resuming the prescribed schedule, especially if the next dose is close.

Do not double a dose to make up for a missed dose. Repeated missed doses should be discussed with the prescriber.

Phenytoin exposure during pregnancy may increase the risk of birth defects and other developmental problems, including heart defects and facial clefts. Seizure frequency may increase during pregnancy, and blood level monitoring may help guide treatment. Newborns exposed during pregnancy can develop a serious bleeding disorder that can be prevented with vitamin K given to the mother before delivery and the newborn after birth.

Phenytoin passes into human milk. Breastfeeding benefits should be weighed against the mother's treatment needs and possible effects on the infant.

The label specifies storage at 20° to 25°C in tight, light-resistant containers. Protect the capsules from moisture to maintain quality. Keep phenytoin and all medicines out of the reach of children.