lectures 48/49 Flashcards
ott - pharmacotherapy of seizure disorders
how was epilepsy classified in 2011?
seizure can either be partial or generalized
a partial seizure can either be simple or complex
how was epilepsy classified in 2017?
focal onset
generalized onset
unknown onset
what medications lower the seizure threshold?
require usual dose –> bupropion, clozapine, theophylline, varenicline, phenothiazine antipsychotics, and CNS stimulants (amphetamines)
require higher/renal dosing –> carbapenems, lithium, meperidine, penicillin, quinolones, tramadol
what type of seizure is most common?
partial, doesn’t matter if its simple or complex
do patients respond better to mono or polytherapy?
mono –> around 50% of pts will have good control with one drug
poly –> most will have good control with 2 drugs
what are risk factors for seizure recurrence?
under 2 years seizure free
onset of seizure after age 12
hx of atypical febrile seizures
2-6 years before good seizure control in treatment
significant number of seizures (>30) before control achieved
partial seizures (which is the most common type)
abnormal EEG throughout treatment
organic neurological disorder - traumatic brain injury, dementia
withdrawal of phenytoin or valproate
what are possible reason for treatment failure?
failure to reach the CNS target
alteration of drug targets in the CNS
drugs missing the real target
what are management strategies to drug-resistant epilepsy?
rule out pseudo-resistance - wrong drug or diagnosis
combination therapy
electrical/surgical intervention
what is status epilepticus?
continuous seizure activity lasting 5 minutes or more, or two or more discrete seizures with incomplete recovery between seizures
what is the first line agent for status epilepticus?
benzodiazepines, most commonly lorazepam or midazolam
what are the phases of status epilepticus treatment?
stabilization 0-5 minutes
initial treatment 5-20
second treatment 20-40
third 40-60
if a person is being treated for status epilepticus, how should they be treated based on phase
stabilization –> no drug therapy
initial if seizure continues –> IV lorazepam and IV midazolam
second if seizure continues –> IV fosphenytoin, IV valproic acid, IV levetiracetam
what limits the infusion rate of phenytoin?
containing propylene glycol which can lead to hypotension
what is fosphenytoin?
prodrug of phenytoin
better IV tolerance of dosing
20 mg PE (phenytoin equivalents)/kg IV
for phenytoin/fosphenytoin loading dose, why is cardiac monitoring required?
due to local reaction called purple glove syndrome
for oral phenytoin, what should be collected in the SAME blood draw?
serum concentration and serum albumin
what is the therapeutic serum concentration range for phenytoin?
10-20 mcg/mL
what is dosing conversion of valproate loading dose?
1:1 mg/mg
IV to PO
what is the desired serum concentration range for valproate?
80 mcg/mL with a range of 50 - 125 mcg/mL
what is the dosing of lamotrigine with a UGT inhibitor (like valproate)?
25 mg QOD x 14d
25 mg QD x14d
50 mg QD x7d
100 mg QD
what is the dosing of lamotrigine without concomitant UGT Drug interactions?
25 mg QD x 14d
50 mg QD x 14d
100 mg QD x7d
200 mg QD
what is the dosing of lamotrigine with UGT inducers (like carbamazepine, phenytoin)?
50 mg QD x 14d
100 mg QD x14d
200 mg QD x7d
400 mg QD
what is an important drug interaction with lamotrigine?
lamotrigine is a UGT substrate, high initial serum concentrations are associated with Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN)
concomitant drug therapy with UGT inducers (carbamazepine, phenytoin) and inhibitors (valproate) need specific dosing
what is the black box warning of carbamazepine or like derivatives (oxcarbazepine, eslicarbazepine)?
anticonvulsant hypersensitivity syndrome so genetic screen for HLA-B*1502 allele PRIOR to initiating
if positive –> DO NOT USE, unless benefit clearly outweighs risk