Question | Answer |
anticonvulsants | stabilize nerve cell membranes and suppress abnormal electrical activity in cerebral cortex |
action of anticonvulsants | 1. suppress sodium influx, prolonging channel inactivation, prevents neuron firing
2. prevents electrical current generated by Ca ions to the t-type calcium channel
3. increases the action of GABA, which inhibits neurotransmitter throughout the brain |
drugs that suppress sodium influx | phenytoin, fosphenytoin, carbamazepine, valproic acid, toprimate, zonisamide, lamotrigine |
drugs that suppress calcium influx | valproic acid and ethosuximide |
drugs that enhance the action of GABA | barbits, benzos, tiagabine |
drug that promotes GABA release | gabapentin |
hydantoins | ☺act by inhibiting sodium influx, stabilize cell membraines, reduce repetitive neuronal firing
☻also used for dysrhythmias by increasing the electrical stimulation threshold in cardiac tissue
♥do not use in pregnancy due to teratogenic effect on fetus
♦drug dose is age related - slower metabolism in older adult means lower dose, high metabolism in children means higher dose
♣dosage is adjusted according to therapeutic plasma or serum levels |
phenytoin therapeutic level and stuff (I am tired of this stuff) | ☺10-12 mcg/mL
☻highly PB
♥IV admin by direct injection into a large vein
♣may be diluted in saline, do NOT use dextrose cause it will precipitate
♠IV infusion rate greater than 50 mg/min may cause HoTN or dysrhythmia, local irritation and sloughing
♦do not give IM |
s/e and a/e of hydantoins | slurred speech, confusion, depression, thrombocytopenia, leukopenia, gingival hyperplasia, hyperglycemia (drug inhibits insulin), n/v, constipation, drowsiness, HA, alopecia, hirsutism, nystagmus |
drug-drug interactions hydantoins | ☺compete with highly protein bound drugs, anticoags, asa
☻barbits, rifampin, ethanol increase hydantoin metabolism
♥sulfonamides and cimetidine increase action by inhibiting liver metabolism
♦antacids, antineoplastic drugs decrease absorption
♣antipsychotics and herbs lower seizure threshold and increase seizure activity |
barbits | phenobarbital - long acting
☺used for: status epilepticus seizures, meningitis, toxic reactions, eclampsia
☻therapeutic level: 20-40 mcg/mL
♥taper to d/c
♦s/e: resp depression, confusion, depression, irritability
a/e: SI, physical dependence |
succinimides | ethosuximide
☺treats absence or petit mal seizures
☻therapeutic range - 40-100 mcg/mL
♥a/e: blood dyscrasias, renal/liver impairment, SLE |
benzos | clonazepam, clorazepate dipotassium, and diazepam
☺clonazepam - petit mal but tolerance may occur w/i 6 months
☻diazepam - acute status epilepticus, must be admin IV, short-term effect, must give phenytoin or phenobarbital during or immediately after |
iminostilbenes | carbamazepine
☺treats refractory seizure disorders that have not responded to other drugs
☻also used for psychiatric disorders, bipolar disorder, trigeminal neuralgia, and etoh w/d
♥therapeutic level: 5-12 mcg/mL
♦no grapefruit juice |
valproate | valproic acid, divalproex sodium (Depakote)
☺not established as safe for small children
☻hepatoxicity
therapeutic level: 50-100 mcg/mL
♥also used for bipolar and migraine
♦avoid during pregnancy |
anticonvulsants and pregnancy | ☺pregnancy causes seizures to ↑ by 25%
☻hypoxia can harm the fetus
♥phenytoin and carbamazepine are linked to fetal abnormalities of the heart and cleft palate, valproic acid is known to cause major congenital malformation
☺anticonvulsants act as inhibitors for vit K contributing to hemorrhage in infants - give oral vit K supp for the last 10 days of pregnancy
☻anticonvulsants increase the loss of folate - take daily folate supp |
anticonvulsants and febrile seizures | ☺usually occur in children 3 mo - 5 yrs old
☻do not use valproic acid in children <2 yo
♥epilepsy develops in 2.5% of children that have febrile seizures
♦phenobarbital or diazepam are used prophylactically |
NC phenytoin | ☺assess pts knowledge regarding medications
☻urinary output must be >1500 mL/day
♥lab values for renal and liver, if both BUN and creatinine are elevated then renal disease is suspected
♦therapeutic range: 10-20 mcg/mL; toxic level 30-50
♣seizure precautions
♠may cause anorexia, make sure pt is receiving adequate nutrition |
teach phenytoin | ☺shake suspension
☻don't get pregnant on phenytoin or valproic acid
♥monitor phenytoin levels closely while pregnant (did you not just hear me tell you not to get pregnant?)
♦no etoh or CNS depressants
♣taper off medication
♠regular dental appts
•get regular lab tests
◘monitor glucose levels closely - hyperglycemia |
s/e of phenytoin | ☺urine will be a harmless pinkish or redish color
☻use a soft toothbrush
♥report sore throat, nosebleeds, bruising - may indicate a blood dyscrasia
♦report gingivitis, nystagmus, slurred speech, s-j syndrome starts with a rash |
status epilepticus tx | ☺diazepam (valium) IV or lorazepam (Ativan)followed by phenytoin IV
☻if seizure continues midazolam (versed) or propofol (diprivan) and then high dose barbiturates
♥admin slowly to avoid resp depression |
clonazepam | ☺used for petit mal, myclonus and status epilepticus |
diazepam (valium) | ☺status epilepticus - drug of choice
☻admin slowly to prevent resp depression
♥repeat q10-15 min up to 30 mg PRN then q2-4 hr PRN
♦also used to treat anxiety and substance abuse w/d |
lorazepam (ativan) | ☺use to treat status epilepticus
☻infusion rate should not exceed 2 mg/min♥
♥also used to treat anxiety and substance abuse w/d |
carbamazepine (tegretol) | ☺for tonic clonic, partial, simple, complex seizures
☻also used to treat bipolar disorder
♥t/r: 5-12 |
gabapentin (neurontin) | ☺used as an adjuctive therapy for partial seizures
☻give with food to prevent GI upset
♥taper to d/c
♦max dose 3600 mg/d - high doses are used short term |
lamotrigine (lamictal) | ☺maintenance dose: 250 mg BID
☻used for partial and tonic clonic, tx of Lennox-Gastaut syndrome
♥blocks sodium influx
♣d/c if rash appears as it may be the start of s-j syndrome |
pregabalin (lyrica) | ☺used for partial seizures and fibromyalgia
☻affects calcium channels in CNS
♥0% PB |
PB for anticonvulsants | all are highly PB except for phenobarbital |
herbal alert | ☺evening primrose and borage may lower seizure threshold
☻gingko may decrease phenytoin effectiveness |