The anti-convulsants, sometimes also
called anti-epileptics, belong to a diverse group of
pharmaceuticals used in prevention of the occurrence
of epileptic seizures. Many typical anticonvulsants
work by blocking voltage-sensitive sodium channels in
the brain. They include Barbiturates, which are drugs
that act as central nervous system (CNS) depressants,
and by virtue of this they produce a wide spectrum of
effects, from mild sedation to anesthesia. Some also
are used as anticonvulsants.
They also include the Benzodiazepines, whcih are a
class of drugs with hypnotic, anxiolytic, anticonvulsive,
amnestic and muscle relaxant properties. They are believed
to act on the GABA receptor GABAA, the activation of
which dampens higher neuronal activity. They began to
be widely prescribed for stress-related ailments in
the 1960s and 1970s. Benzodiazepines are often used
for short-term relief of severe, disabling anxiety.
Long-term use can be problematic due to the development
of tolerance and dependency. These drugs are preferred
to the use of barbiturates because they have a lower
abuse potential and relatively lower adverse reactions
and interactions. However, drowsiness, ataxia, confusion,
vertigo, impaired judgement, and a number of other effects
are still common.
Two very important Anti-convulsant drugs used in neurosurgery
are Phenytoin and Carbamazepine.
See further information about them here.
Phenytoin sodium (marketed as Dilantin® in the USA
and as Epanutin® in the UK) is a commonly used antiepileptic
or antiseizure drug. It can be injected or taken orally.
It was first synthesized in 1908, but is was not until
1938 that scientists discovered phenytoin's usefulness
for controlling seizures, without the sedation effects
associated with phenobarbital. There are some indications
that phenytoin has other effects, including anxiety
control and mood stabilisation, although it has never
been approved for those purposes by the USA FDA. It
is used especially to prevent tonic-clonic (grand mal)
epileptic seizures, and complex partial seizures (psychomotor
seizures). It may be used alone or with phenobarbital
or other anti-convulsants.
The dosing of phenytoin is very patient specific. It
may be given once, twice, or three times daily. Doses
are often adjusted to find the optimal dose, based on
measurement of blood levels. Taking phenytoin with food
may reduce some of the side effects. Elderly patients,
debilitated persons, and patients with certain kidney
or liver diseases may need lower doses. The suspension
should not be given at the same time as tube feedings.
There are many potential drug interactions with
phenytoin. Phenytoin can increase the metabolism (elimination)
of many drugs, reducing their concentrations in the
body. Drugs that may be affected include: digoxin, carbamazepine,
clonazepam, corticosteroids (e.g. prednisone), cyclosporine,
disopyramide, doxycycline, estrogens, felodipine, levodopa,
lidocaine, methadone, mexiletine, oral contraceptives,
paroxetine, quinidine, tacrolimus, theophylline, phenobarbital,
and warfarin. Phenytoin can interact with these drugs
not only when it is added to therapy but also when it
is discontinued. In the latter case, the concentration
of the other drugs may increase.
Phenytoin's metabolism may be affected by other drugs.
Drugs that can reduce the amount of phenytoin in the
body include rifampin and phenobarbital. Drugs that
increase phenytoin concentrations include amiodarone,
chloramphenicol, cimetidine, disulfiram, fluconazole,
fluoxetine, isoniazid (INH), omeprazole, and paroxetine.
Thus, measuring levels of phenytoin in the blood may
be necessary when patients begin or discontinue other
The oral absorption of phenytoin can be reduced by any
of the following: antacids containing magnesium, calcium
carbonate, or aluminum; calcium salts; or enteral feeding
products (tube feedings). Separating the administration
of phenytoin and enteral feeding products, antacids,
or calcium salts by at least 2 hours will help avoid
Many varied adverse effects can occur during phenytoin
therapy including dizziness, drowsiness, difficulty
focusing (vision), unsteady gate, tiredness, abnormal
involuntary movements, nausea, vomiting, constipation,
abdominal pain, and loss of appetite. Children and young
adults can develop overgrowth of the gums during long-term
therapy which requires regular treatment by a dentist.
Good oral hygiene and gum massage may reduce the risk.
Rashes can occur in between 1 in 20 and 1 in 10 persons;
some may be severe. Additionally, darkening coloration
of the skin may develop (more commonly in women). Phenytoin
can produce unusual growth of hair in some patients.
This reaction most commonly affects the arms and legs
but can also affect the trunk and face; it may be irreversible.
Various lymph node reactions have been reported with
phenytoin therapy. Lymph nodes may swell up, sometimes
painfully. Phenytoin cause serum glucose to rise. Thus,
blood sugar should be monitored closely when phenytoin
is administered to patients with diabetes. Phenytoin
can potentially injure the liver although this is an
uncommon occurrence. Phenytoin can cause the platelet
or white blood cell counts to drop, increasing the risk
of bleeding or infection, respectively. Phenytoin also
can cause anemia. Because it interferes with vitamin
D metabolism, phenytoin can cause weakening of the bones
(osteomalacia). Phenytoin can cause sexual dysfunction
including decreased libido, impotence, and priapism
(painful, prolonged erections).
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Carbamazepine is an anti-seizure medication, and mood
stabilising drug, used primarily in the treatment of
epilepsy and bipolar disorder; but also used to treat
schizophrenia and trigeminal neuralgia, a painful nerve
condition of the face. Recurrent seizures (epilepsy)
are divided into two main categories according to how
much of the brain is involved, partial and generalized
epilepsy (which includes petit mal, grand mal, and myoclonic
epilepsy). Seizures are called "simple" if
there is no loss of consciousness and "complex"
if there is. Medicines that inhibit seizures are called
anti-convulsants. Carbamazepine works as an anti-convulsant
for partial and grand mal seizures by reducing or blocking
certain responses in the brain. It is also used for
treating trigeminal neuralgia. One dosage form, Equetro,
has been approved for treating bipolar disorder.
Carbamazepine is used in the treatment of simple and
complex partial seizures and in generalized seizures
of the grand mal type.a. Equetrol is used to treat bipolar
Carbamazepine may be taken with or without food.
Carbamazepine is excreted by the kidney and metabolized
by the liver and dosages may need to be lowered in patients
with liver or kidney dysfunction. Drug blood levels
of carbamazepine can be followed.
Carbamazepine interacts with multiple drugs and caution
should be used in combining other medicines with it.
Lower levels of carbamazepine are seen when administrated
with phenobarbital, phenytoin, or primidone. Warfarin,
phenytoin, theophylline, and valproic acid are more
rapidly metabolized with carbamazepine, while carbamazepine
levels are elevated when taken with erythromycin, cimetidine,
propoxyphene, and calcium channel blockers. Carbamazepine
also increases the metabolism (destruction) of the hormones
in birth control pills and can reduce the effectiveness
of birth control pills. Unexpected pregnancies have
occurred in patients taking both carbamazepine and birth
Serious side effects include dangerously low red and
white blood cell counts. Severe skin reactions can occur
as well as serious liver abnormalities, such as hepatitis,
resulting in jaundice. Low sodium levels and thyroid
abnormalities have been described. Minor more common
side effects include dizziness, unsteadiness, nausea,
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