Seizure Medications Flashcards
Levetiracetam/Keppra uses
Go-to, used in all seizure types
Keppra dosing
500mg BID, titrate q2w until at max recommended dose of 1.5g BID
Keppra side effects
Well tolerated, some weight gain
Keppra monitoring
Dose adjust based on GFR- watch renal function
Keppra enhances what drugs?
CNS depressants
Oxcarbazepine uses
Adjunctive therapy in partial seizure treatment in children 6+
Initial oxcarbazepine dosing
5mg/kg/day, weekly increments of 5mg/kg/day
Target oxcarbazepine dosing
30-50mg/kg/day
Dosing frequency of oxcarbazepine
BID
Oxcarbazepine side effects
Most common in children: somnolence, HA, dizziness, N/V, rash is potentially fatal but reversible
Oxcarbazepine monitoring
Sodium, hepatic function
Get baseline electrolytes and hepatic enzymes
Oxcarbazepine and drug interactions
Lower potential for drug interactions because of low protein binding, hepatic enzyme induction, MHD eliminated by the kidneys
Lamotrigine uses
Partial onset seizures
Initial lamotrigine dose
0.5mg/kg/day divided BID x2 weeks, then 1mg/kg/day x2 weeks, then increase 1mg/kg/day q2w until response
Maintenance lamotrigine dose
5-15mg/kg/day div BID
MDD of lamotrigine
400mg/day
When does the dose of lamotrigine need to be decreased?
Patients taking VPA
Lamotrigine side effect
SJS! More likely to occur with fast titration
Other info about lamotrigine
Broad spectrum of activity, low teratogenic potential, nonsedative
Gabapentin uses
Partial seizures, also useful in comorbid neuropathic pain/mood stabilization in BPD
Initial gabapentin dosing
30mg/kg/day
Max gabapentin dosing
1800mg/day
Dosing frequency of gabapentin
TID
Gabapentin side effects
Somnolence, dizziness, ataxia, weight gain with higher doses
Lower incidence of neurotoxic side effects
That one weird fact about gabapentin
Doses 2-3x higher often necessary to achieve max benefits
With a higher dose, lower % is absorbed
Gabapentin interactions with other drugs
No PK interactions, pure renal elimination and no binding to serum proteins
Phenytoin use
Generalized seizures
Phenytoin dosing
200-400mg
Concentration-dependent phenytoin side effects
nystagmus, double-vision, blurred vision, incoordination, drowsiness, dizziness, HA
Idiosyncratic phenytoin side effects
aplastic anemia, granulocytopenia, hepatotoxicity, rash, SJS, Lupus-like reaction
Chronic phenytoin side effects
gingival hyperplasia, acne, hirsutism, peripheral neuropathy, chronic cerebellar damage, megaloblastic anemia, osteoporosis, fetal vitamin K depletion
Phenytoin monitoring
Baseline CBC and liver enzymes, bone density screen for osteoporosis, normal TDM stuff
Phenytoin PK/PD: protein binding
Highly protein bound
Phenytoin PK/PD: hepatic metabolism
Capacity-limited
Phenytoin tmax
4-12h
Phenytoin PK/PD: toxicity
Has both concentration independent and dependent toxicity
Fosphenytoin is used when?
IV, usually given in status epilepticus after IV benzo administration
Valproate initial dosing
15mg/kg/day initially in 2-3 divided doses, increasing in 5-10mg/kg/day increments at weekly intervals to a max of 60mg/kg/day
Valproate maintenance dosing
15-40mg/kg/day in 3 divided doses
When to reduce starting dose of valproate
Elderly patients
Valproate side effects
N/V/D, abdominal cramps, transient elevations in LFTs
Occasionally: drowsiness, ataxia, tremor, behavioral disturbances, transient hair loss, asymptomatic hyperammonemia, weight gain
Drowsiness and ataxia are more likely in patients taking valproate with what?
Other AEDs
Valproate monitoring
Baseline LFTs, platelets, repeat LFTs frequently (esp. in first 6 months of treatment)
Monitor coagulation tests prior to surgery
Valproate CI
Hepatic disease/dysfunction
Target valproate levels
50-120mg/L
Drugs that can lower valproate levels
Carbamazepine, lamotrigine, phenytoin, rifampin
Drugs that can increase valproate levels
ASA, chlorpromazine, cimetidine, felbamate
Drugs levels that can increase by valproate
Lamotrigine, phenobarbital
Valproate can do what to other AEDs at protein binding sites?
Displace them
Carbamazepine uses
Partial and secondary generalized seizures
Adult dosing for carbamazepine
600-2,000mg/day
Kids dosing for carbamazepine
10-40mg/kg/day
Carbamazepine dosing frequency
TID or QID, but BID for SR formulation
Carbamazepine side effects that can be minimized by slow titration
dizziness, drowsiness, HA, diplopia, N/V
Carbamazepine side effects: hyponatremia and water intoxication…what’s it caused by?
Carbamazepine monotherapy, elevated serum levels, age >25, vomiting, diarrhea
Carbamazepine monitoring
Baseline CBC and platelet counts
Serum levels once weekly in first month of therapy
Target carbamazepine serum levels
4-12mg/L
Carbamazepine and MAOIs
D/C MAOI at least 14 days before starting carbamazepine
Carbamazepine can do what to CYP3A4 drugs?
Stimulate their metabolism
Drugs that can inhibit carbamazepine metabolism
Cimetidine, clarithromycin, danazol, erythromycin, fluoxetine
How long does it take for carbamazepine and valproate to reach Css?
2-4 days
That may not last for long with carbamazepine because it goes through autoinduction
Topiramate uses
Focal (partial) onset seizures, primary generalizes tonic-clonic seizures
Topiramate initial dosing
50mg/day, increase in 50mg dose increments until max dose of 200mg/day in 1-2 divided doses. Could go up to 400mg/day depending on formulation
Topiramate elderly dosing
25mg/day, titrated up 25mg weekly until effective dose reached
Topiramate kids dosing
initial- 1-3mg/kg/day at night x1 week, increase at 1-2 week intervals. Maintenance: 5-9mg/kg/day, max is 400mg/day
Topiramate side effects
Dizziness, drowsiness, fatigue, metabolic acidosis, kidney stones, secondary acute angle closure glaucoma, hypohidrosis, hyperthermia, suicidal ideation, anorexia/weight loss, finger/toe numbness
Topiramate monitoring
Electrolytes, SCr, acute acidosis, ammonia levels, IOP, screen for eating disorder
Topiramate has synergistic effects with what other AED and why?
Lamotrigine, because they have different MoAs!
