NR-566: Final Exam Study Guide - Week 7 (Seizure Disorders)
What are the treatment options for absence seizures?
traditional: ethosuximide, valproic acid
newer: lamotrigine
What is the MOA of phenytoin?
selective inhibition of Na+ channels, slowing the recovery of Na+ channels from an inactive
state back to an active state - suppressing action potentials and activity of seizure-generating
neurons
How can phenytoin influence the induction of hepatic enzymes?
1. stimulates synthesis of enzymes CYP2C8, CYP2CP, CYP3A4 & CYP2B
2. induction of these enzymes can decrease the effects of OCs, warfarin, and glucocorticoids
3. if doses of phenytoin are slightly greater than those needed for therapeutic effects, the liver's
capacity to metabolize the drug will be overwhelmed and l/t a dramatic rise of levels
How is the dosage of phenytoin determined?
serum drug levels, trough levels, & assessment of seizure control
What are the therapeutic & prescriptive indications for phenytoin?
1. can treat all major forms of epilepsy except absence seziures
2. especially therapeutic for tonic-clonic seizures
3. drug of choice for adults & older children (carbamazepine is drug of choice for younger
children)
What are some major adverse effects noted with phenytoin?
1. CNS effects - nystagmus, sedation, ataxia, diplopia, cognitive impairment
2. gingival hyperplasia - folic acid can decrease overgrowth
3. dermatologic effects - SJS, TEN
4. drug reaction w/ eosinophilia & systemic symptoms (DRESS) - skin eruptions,
lymphadenopathy, severe & multi-organ involvement (hepatic, renal, pulmonary, & hematologic
system)
5. dysrhythmias & hypotension when given IV for status epileptics (SE)
What is a genetic consideration regarding phenytoin therapy?
serious dermatologic effects and DRESS are associated with the genetic mutation human
leukocyte antigen (HLA)-B*1502 - occurs mostly in Asian descent (test for this genetic mutation
before initiating treatment)
What are the treatment options for absence seizures?
traditional: ethosuximide, valproic acid
newer: lamotrigine
What is the MOA of phenytoin?
selective inhibition of Na+ channels, slowing the recovery of Na+ channels from an inactive
state back to an active state - suppressing action potentials and activity of seizure-generating
neurons
How can phenytoin influence the induction of hepatic enzymes?
1. stimulates synthesis of enzymes CYP2C8, CYP2CP, CYP3A4 & CYP2B
2. induction of these enzymes can decrease the effects of OCs, warfarin, and glucocorticoids
3. if doses of phenytoin are slightly greater than those needed for therapeutic effects, the liver's
capacity to metabolize the drug will be overwhelmed and l/t a dramatic rise of levels
How is the dosage of phenytoin determined?
serum drug levels, trough levels, & assessment of seizure control
What are the therapeutic & prescriptive indications for phenytoin?
1. can treat all major forms of epilepsy except absence seziures
2. especially therapeutic for tonic-clonic seizures
3. drug of choice for adults & older children (carbamazepine is drug of choice for younger
children)
What are some major adverse effects noted with phenytoin?
1. CNS effects - nystagmus, sedation, ataxia, diplopia, cognitive impairment
2. gingival hyperplasia - folic acid can decrease overgrowth
3. dermatologic effects - SJS, TEN
4. drug reaction w/ eosinophilia & systemic symptoms (DRESS) - skin eruptions,
lymphadenopathy, severe & multi-organ involvement (hepatic, renal, pulmonary, & hematologic
system)
5. dysrhythmias & hypotension when given IV for status epileptics (SE)
What is a genetic consideration regarding phenytoin therapy?
serious dermatologic effects and DRESS are associated with the genetic mutation human
leukocyte antigen (HLA)-B*1502 - occurs mostly in Asian descent (test for this genetic mutation
before initiating treatment)
