Pharmacology for Dentistry

108 Section 2/ Drugs Acting on CNS

Oxcarbazepine is completely absorbed
following oral administration and is exten-
sively metabolised to its pharmacologically
active 10-monohydroxy metabolite.

Adverse reactions include dizziness,
diplopia, fatigue, nausea, vomiting,
dyspepsia, ataxia, abnormal vision, tremor
etc.

SUCCINIMIDES

ETHOSUXIMIDE

Ethosuximide is most commonly used
antiepileptic agent in the treatment of
petitmal epilepsy. It acts on thalamocortical
system by selectively suppressing T current
without affecting other types of Ca2+ or Na+
currents. It is completely absorbed from
gastrointestinal tract and present in plasma
in free form and approximately 20% is
excreted unchanged in urine and remaining
portion is metabolized in liver.

Adverse effects include anorexia, nau-
sea, vomiting, drowsiness, dizziness, agita-
tion, skin rashes and blood dyscrasias and
rarely cause systemic lupus erythematosus.

METHSUXIMIDE

It is similar to ethosuximide and used
along with the other drugs in the treatment
of temporal lobe epilepsy.

ALIPHATIC CARBOXYLIC ACID

SODIUM VALPROATE (VALPROIC

ACID)

Sodium valproate increases the levels of
GABA in the brain and increases the

responses to GABA in the postsynaptic

neurons. Also sodium valproate affects

potassium flow across the neurons. The result

of these effects is inhibition of initiation as well

as spread of epileptic activity in the neurons.

Valproate has antiepileptic efficacy in

different types of epilepsy. It is therefore

sometimes called the broad range antiepileptic

drug. It has no significant hypnosedative

effects nor does it have respiratory depressant

activity. In addition it does not have

undesirable effects on blood pressure, heart

rate, kidney function and body temperature.

Absorption is rapid and complete. Protein

binding is between 80 to 95 percent and the

elimination half life is 8 to 22 hours. It is

metabolised in the liver and is excreted by the

kidney. There is no presystemic metabolism.

Adverse effects include anorexia,

nausea, vomiting, diarrhoea and/or

constipation, weight gain, skin rash; hair

loss, neutropenia, tremors and ataxia are

occasionally reported. Valproic acid is

contraindicated in liver disease, especially

cirrhosis, pregnancy and hypersensitivity.

BENZODIAZEPINES

CLONAZEPAM

It is a benzodiazepine useful in the

treatment of petitmal epilepsy, myoclonic

seizures and infantile spasms. It is used in

the treatment of petitmal epilepsy not

responding to ethosuximide and sodium

valproate. Clonazepam and diazepam act by

increasing the effectiveness of the

inhibitory neurotransmitter GABA, within

the central nervous system.