ANTICONVULSANTS
ANTICONVULSANTS
2010-2011
SEIZURE – uncontrollable physiologic response to abnormal electrical discharges in CNS
EPILEPSY – seizure disorder – the seizure asso. w/ epilepsy results from abnormal electric discharges from cerebral neurons – char. by loss / disturbance of consciousness & usually by a convulsion ( abnormal motor reaction )
Factors affecting seizure occurrence:
1. level of basal seizure threshold
2. presence of foci - initiate abnormal stimuli
a. inflammation
b. abnormal pressure
c. scar from previous lesion
3. irritation of nerve cell due to bio-chemical changes
Ex. Hypoxemia, hypoglycemia, electrolyte imbal., acid-base imbal., alcohol or drug withdrawal
Action of Anticonvulsants:
1. suppress Na influx -- preventing neuron firing ex. phenytoin, fosphenytoin, carbamazepine, oxcarbazepine, valproic acid, topiramate, zonisamide & lamotrigine.
2. suppress Ca influx -- prevents electric current generated by Ca ions ex. Valproic acid & ethosuximide
3. increase the action of GABA ( Gamma-aminobutyric acid ) -- inhibits neurotransmitter throughout the brain.
Ex. Gabapentin -- promotes GABA release Vigabatrin -- inhibits degradation of GABA from enzyme action Barbiturates, benzodiazepines & tiagabine --- enhances the action of GABA
CLASSIFICATION OF SEIZURES
Generalized Seizure - Tonic-clonic seizure convulsive and nonconvulsive -- both cerebral hemispheres of the brain grand mal seizure -- most common form of seizure tonic phase -- skeletal muscles contract for 3-5 sec. clonic phase -- dysrhythmic muscular contraction / jerkiness of legs and arms for 2-4 min.
Tonic seizure – sustained muscle contraction
Clonic seizure – dysrhythmic muscle contraction
Absence seizure – also called petit mal seizure -- brief loss of consciousness 4 sec. – usually occurs in children
> treated with clonazepam but it may lose its effectiveness after 3 months of therapy
Myoclonic
2010-2011
SEIZURE – uncontrollable physiologic response to abnormal electrical discharges in CNS
EPILEPSY – seizure disorder – the seizure asso. w/ epilepsy results from abnormal electric discharges from cerebral neurons – char. by loss / disturbance of consciousness & usually by a convulsion ( abnormal motor reaction )
Factors affecting seizure occurrence:
1. level of basal seizure threshold
2. presence of foci - initiate abnormal stimuli
a. inflammation
b. abnormal pressure
c. scar from previous lesion
3. irritation of nerve cell due to bio-chemical changes
Ex. Hypoxemia, hypoglycemia, electrolyte imbal., acid-base imbal., alcohol or drug withdrawal
Action of Anticonvulsants:
1. suppress Na influx -- preventing neuron firing ex. phenytoin, fosphenytoin, carbamazepine, oxcarbazepine, valproic acid, topiramate, zonisamide & lamotrigine.
2. suppress Ca influx -- prevents electric current generated by Ca ions ex. Valproic acid & ethosuximide
3. increase the action of GABA ( Gamma-aminobutyric acid ) -- inhibits neurotransmitter throughout the brain.
Ex. Gabapentin -- promotes GABA release Vigabatrin -- inhibits degradation of GABA from enzyme action Barbiturates, benzodiazepines & tiagabine --- enhances the action of GABA
CLASSIFICATION OF SEIZURES
Generalized Seizure - Tonic-clonic seizure convulsive and nonconvulsive -- both cerebral hemispheres of the brain grand mal seizure -- most common form of seizure tonic phase -- skeletal muscles contract for 3-5 sec. clonic phase -- dysrhythmic muscular contraction / jerkiness of legs and arms for 2-4 min.
Tonic seizure – sustained muscle contraction
Clonic seizure – dysrhythmic muscle contraction
Absence seizure – also called petit mal seizure -- brief loss of consciousness 4 sec. – usually occurs in children
> treated with clonazepam but it may lose its effectiveness after 3 months of therapy
Myoclonic