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35 Cards in this Set

  • Front
  • Back
Common etiologies of seizures.
Stress can cause seizures in those with seizure disorders
Menstruation can cause increased seizure in some women
Low trough (even in therapeutic range)
Metabolic Disorders
What is your target serum level for Phenytoin?
Total 10-20
Free 0.5-3
What is the DDI between Phenytoin and OC's?
Phenytoin decreases the efficacy of OC's.

You can use an estrogen has has 50 mcg of estrogen or use a second form of birth control if breakthrough bleeding occurs.
What is phenytoin's mechanism of action?
Sodium Channel Blocker
What is normal albumin?

Low albumin = High free phenytoin
Breakthrough bleeding is the marker of the OC being ineffective.

What are the goals of treatment in seizure disorders?
Maintain or decrease number of monthly seizures
Minimize adverse drug events
Maintain or improve quality of life
Phenytoin has non-linear kinetics.
Doubling a dose can get you an exponentially higher serum level.
Valproic acid - Phenytoin DDI.
Valproic acid will increase Phenytoin levels

Valproic acid is teratogenic - Do not put a women of childbearing age on this!
What would you want to add to a female of childbearing age's drug regimen?
Folic acid to reduce incidence of birth defects if birth control fails

0.4 mg po daily

Supplemental Vitamin D and Calcium b/c AED's can interfere with vitamin D metabolism and are associated with osteomalacia and osteoporosis.
How do you monitor Phenytoin therapy?
Phenytoin levels (average half life is 24 hours, so check in about a week)
Seizure frequency (seizure diary)
Toxicity (SE's = sedation, blurred vision, HA)
What would you counsel patients on a patient on Phenytoin therapy?
Vitamin D/Calcium - Prenatal vitamin
Use barrier contraception while you assess if breakthrough bleeding with occur
Seizure first aid (what to do if you have a seizure)
If a patient is not having seizures but is having side effects, what is your course of action?
Lower the phenytoin dose and start a second AED immediately.
Add the second AED and wait until it is therapeutic to lower the phenytoin dose.
If considering a second AED, what are your options and what is your thought process?
Lamotrigine is a good choice

Valproic acid - avoid in females of childbearing age
***All of these cause more cognitive effects like sluggishness***
Lamotrigine - OC DDI
OC's decrease Lamotrigine levels

Increase Lamotrigine dose
Phenytoin - Lamotrigine DDI
Phenytoin induces Lamotrigine metabolism via non-CYP mechanism
What drugs do you want to avoid in a patient with an abnormal hepatic panel?
Valproic acid - Can cause acute hepatic failure

You can consider Carbmazepine, Levetiracetam, Phenytoin, but you want to monitor levels.
What drugs are renally eliminated?
***Not a contraindication in impaired liver function, but need to monitor levels and adjust dose***
What drugs would you avoid if your patient was concerned with weight gain?
Valproic acid
Topiramate - weight loss!!!
What drug would you avoid if a patient developed a rash while on phenytoin?
Carbamazepine - higher incidence of rash - don't necessarily have to avoid unless it is severe like SJS
What factors favor successful withdrawal of AEDs?
1) Seizure control within 1 year of onset
2) Seizure free period of > 2 yrs
3) Seizure onset between ages 2 and 35
4) Normal neuro exam, EEG and IQ
Relapse rates
< 39% in adults
< 32% in children
Risk of pregnancy in a patient with epilepsy
Increase rate of seizures
Increase rate of miscarriage
Low birth weight

Many women have normal pregnancy however
Specific recommendations on how to withdraw AEDs
Remove AED over 6 months one drug at a time.
Teratogenic AEDs
Phenytoin - Category D - Defects

Lamotrigine - Folate deficiency associated defects - Category C

If Phenytoin is dc'ed what would happen to Lamotrigine level?
It would increase because Phenytoin is an inducer and if you take it away the other drug will increase.
When do you expect to see a relapse if an AED is discontinued?
Within a year after AED withdrawal. After this time your risk if much less of relapse.
Treatment of absence seizures.
Ethosuximide - Fewest side effects
Valproic acid
Children require higher doses because children have a higher rate of metabolism. This was in reference to a 13 year old.
If the patient was 18 yo, she said she would probably go with the same dose as an adult.
Important points to counsel on in Ethosuximide
DDI - OC's
Valproic acid
Weight gain
Thrombocytopenia, Impaired platelet aggregation
DDI (Not with OC)
Counseling with Carbamezipine.
Visual disturbances
Carbamazepine counseling
Take with food
Visual disturbances
Don't drink alcohol
Can't drive
Seizure first aid (Gently help them to the floor, remove harmful objects, afterwards move them on their side so they don't choke, do not put anything their mouth, do not leave them alone afterwards)
Drug interactions
Side effects
Carbamazepine levels (Auto-induction around day 3-5 and completed in 3-4 weeks. You want to check level in 2-3 weeks)
If the patient is experiencing side effects (nausea, vomiting) while on Carbamazepine.
This can be caused by either GI irritation in which switching to the CR formulation would help. Or it could be caused by a brain stem defect in which switching to the CR formulation would not help)