Greetings!
Thank you everyone for a great discussion of AED's (and Cardiovascular Drugs) today. As promised, below are the answers to the remaining 2 questions we did not have time to get to today. If you have additional questions about this material or any other material discussed today, I encourage you to post to the Q&A Discussion board.
M) What other concerns might you have regarding this medication given LT's prior medical history? What other medications indicated to treat LT's seizure type would not be ideal for similar reasons?
This question is really getting at which medications have CYP interactions. As discussed in class and in the pre-lecture slides, many of the AED's affect liver enzymes, that is induce (increase the production of) CYP450 enzymes. This can affect the concentration of other drugs the patient may be taking that are metabolized by CYP450. Additionally, some AED's are simply CYP450 substrates - meaning that they are metabolized by CYP450 enzymes - and may be affected by other drugs that use the same CYP450 pathway or are themselves inducers or inhibitors. Using drug information resources, you can look up the drugs that LT is taking and realize that Losartan, Warfarin, a well as Atorvastatin and Amlodipine (the components of Caduet) are all metabolized by CYP450 enzymes. Therefore, we would expect an inducer of CYP450 to decrease the concentration of these drugs (because there is more enzyme to metabolize these drugs to inactive forms). The role of a pharmacist in this scenario would be to examine if there are significant drug interactions and how to manage them (whether dosage adjustments are necessary or not). The role of a physical therapist would be to educate the patient on the importance of informing their prescriber and pharmacist about ALL the drugs, supplements, OTC products, vitamins and minerals that they are taking to ensure these interactions are being managed.
Specific to LT, the medications of concern would be Phenytoin and Carbamazepine due to CYP induction and Valproic Acid as it carries a special interaction where it can increase the bleed risk of Warfarin.
N) What would you tell LT regarding her plans to treat her nephew with the AED she uses for her seizure disorder?
As indicated in the slides, Carbamazepine is not indicated for the treatment of absence-type seizures, which LT's nephew has. The usual treatment for absence seizures is ethosuxamide though there are other options - carbamazepine just isn't one of them. Additionally, LT's nephew was not prescribed this medication so even if the medication LT was taking had an indication for her nephews seizure type, it would be unwise for LT to give him the medication as he has not been evaluated to use this medication. Carbamazepine can cause a severe epidermal necrosis known as Steven Johnsons Syndrome in some patients (do not image search unless you have a strong stomach) and should not be given to someone outside of the supervision of a doctor. Finally, the medication has to reach steady state before it is effective and thus would not be use to control seizures for duration of only a day or two.