General
Description & Use
Phenytoin
sodium is a commonly used anti epileptic drug. Phenytoin acts
to dampen the unwanted, runaway brain activity seen in seizure
by reducing electrical conductance among brain cells by stabilizing
the inactive state of voltage gated sodium channels. Aside from
seizures, it is an option in the treatment of trigeminal neuralgia
as well as certain cardiac arrhythmias. Phenytoin
sodium has been marketed as Phenytek by Mylan Laboratories, previously
Bertek Pharmaceuticals, and Dilantin; also Dilantin Kapseals and
Dilantin Infatabs in the USA, Eptoin by Abbott Group in India
and as Epanutin in the UK and Israel, by Parke-Davis, now part
of Pfizer. (Diphenin, Dipheninum), PhydumTM in form of tab./inj.
by Quadra labs pvt. ltd. in India.
Dilantin is an anti-epileptic drug, also called an anticonvulsant.
It works by slowing down impulses in the brain that cause seizures.
Dilantin is used to control seizures (epilepsy). It is not made
to treat all types of seizures, and your doctor will determine
if it is the right medication for you. Dilantin may also be used
for purposes other than those listed in this medication guide.
Important
information about Dilantin
If you are taking Dilantin to prevent seizures, keep taking the
medication even if you feel fine. You may have an increase in
seizures if you stop taking Dilantin. Follow your doctors instructions.
Do not change your dose of Dilantin without your doctors advice.
Tell your doctor if the medication does not seem to work as well
in treating your condition. Carry an ID card or wear a medical
alert bracelet stating that you are taking Dilantin, in case of
emergency. Any doctor, dentist, or emergency medical care provider
who treats you should know that you are taking a seizure medication.
Side-effects
At therapeutic doses, phenytoin produces horizontal gaze nystagmus,
which is harmless but occasionally tested for by law enforcement
as a marker for alcohol intoxication (which can also produce nystagmus).
At toxic doses, patients experience sedation, cerebellar ataxia,
and ophthalmoparesis, as well as paradoxical seizures. Idiosyncratic
side effects of phenytoin, as with other anticonvulsants, include
rash and severe allergic reactions.
It
has been suggested that phenytoin causes a reduction in folic
acid levels, predisposing patients to megaloblastic anemia. Folic
acid is presented as polyglutamate in foods, it is then converted
into monoglutamates by intestinal conjugase. Phenytoin acts by
inhibiting this enzyme therefore causing folate deficiency.
Phenytoin
is a known teratogen. The syndrome consists of craniofacial anomalies
(broad nasal bridge, cleft lip and palate, microcephaly) and a
mild form of mental retardation (average IQ=71). This syndrome
resembles the well-described Fetal Alcohol Syndrome and has also
been called the "fetal hydantoin syndrome."
Phenytoin
may accumulate in the cerebral cortex over long periods of time,
as well as causing atrophy of the cerebellum when administered
at chronically high levels. Despite this, the drug has a long
history of safe use, making it one of the more popular anti-convulsants
prescribed by doctors, and a common "first line of defense"
in seizure cases. Recently phenytoin is suggested to be a human
carcinogen.
Due
to patent expiration, phenytoin is available in generic form and
several branded forms at relatively low cost, making it one of
the more affordable seizure control medications. It is available
in extended release capsules and injectable forms, though the
injectable formulation is rapidly losing ground to fosphenytoin
(an important side note is that fosphenytoin has to be dephosphorylated
before it can metabolized for use which can take an extra 15 minutes).
Some generic formulations of phenytoin have been felt to be less
reliable with respect to time-release than their branded counterparts.
In some cases, this can be related to complications which arise
between the alternative protein bond release mechanisms used in
the generic versions, and those individuals with high metabolic
rates.
Phenytoin
has been associated with drug induced gingival enlargement (hyperplasia)
in the oral cavity probably due to above mentioned folate defiency.
Plasma concentrations needed to induce gingival lesions has not
been clearly defined. Effects consist of the following: bleeding
upon probing, increased gingival exudate, pronounced gingival
inflammatory response to plaque levels, associated in some instances
with bone loss but without tooth detachment.
Before
taking Dilantin
Do not use this medication if you are allergic to Dilantin.
Before taking this medication, tell your doctor if you are allergic
to any drugs, or if you have:
