Mechanisms that medications can work to control seizures, so basically when we’re choosing medication for epilepsy, we want to choose a drug based on how effective the drug is for the particular seizure type. different side effects that the drug may have and whether the patient thinks that they will be tolerable or not, interactions with other medications that the patient
Is currently taking, interactions with other disease states the patient has, like definitely liver and kidney function, and then different lifestyle or patient preferences which we’ll get into later. we’re going to group the anti-epileptics into traditional anti-epileptics which are older anti-epileptics and then the newer agents. typically when we think of older agents, we
Know that their efficacy in different seizure types is well-established, we know their place in epilepsy and the different seizure types, and we know that there’s been a lot of research conducted on them. some cons to to the traditional anti-epileptics are that they’re less well tolerated, they have quite a few side effects, typically they have complex there can be different
Things that happen with their distribution in the body and their metabolism and how they’re absorbed, and there’s quite a few drug-drug interactions as well. with the newer agents, the good things about them is that they’re better tolerated and there are less drug-drug interactions and they’re typically thought of as being safer in pregnancy, but some cons is that since
They are newer their efficacy is less well established, and there’s a lot less research there’s a lot of evolution in finding exactly where they fit in efficacy in controlling seizures. there’s five medications that we’ll be discussing today. the first one is carbamazepine or tegretol, and we can think of this one as seizures being ‘curbed’ or ‘car’-ved we can think of
If we think of the tegretol, we can think of the ending as kind of like control, divalproex or depakote, we can think of the ‘-val-‘ in divalproex looking like ‘-vol-‘ in convulsions. phenytoin or dilantin, that will be the third of the three traditional anti-epileptics. two newer agents are gabapentin or neurontin and pregabalin or lyrica. but they don’t actually have
A direct effect on gaba receptors in the brain, which is one mechanism of action that rhabdomyolysis is?’ and so the five answers that we’ll have for the remainder of the video is a) carbamazepine, a) carbamazepine, b) divalproex, and then c) phenytoin are all incorrect because they are all older agents and they’re all not controlled. gabapentin is incorrect because even
Though it is a newer antiepileptic, it’s not controlled and has less of a rhabdo risk. pregabalin is correct because it is the only controlled substance and it’s controlled because of its potential risk of abuse. there is a risk of rhabdomyolysis, which is just the severe breakdown of muscle tissue. now we’ll go through four more practice questions, and we will keep all
Of the answers the same and in the same order but we will change the question to make each answer correct. ‘an older antiepileptic that can undergo auto-induction and can cause agranulocytosis as well as a severe skin rash?’ the correct answer is a) carbamazepine. b) divalproex is incorrect because it doesn’t cause autoinduction, a rash or agranulocytosis. phenytoin is
Incorrect because although it can cause a rash and agranulocytosis, there is no autoinduction. d) and e), gabapentin and pregabalin, are incorrect because these are newer antiepileptic agents. autoinduction is a form of metabolism, and basically the way carbamazepine works is it induces its own metabolism. we’ll initially see increases in serum concentration, but shortly
After starting therapy the half-life of the drug in the body decreases, which means that we’re clearing the drug faster, so this will lead to lower concentrations in the blood. carbamazepine also has a black box indication for agranulocytosis which are both just fancy words for saying that these are severe drops in white blood cells and in red blood cells. a severe skin
Rash – the skin rash is known as stevens-johnson syndrome -which can lead to skin sloughing. pancreatitis is?’ the correct answer is b) divalproex. but they don’t have any effect on ammonia, liver or the pancreas. gabapentin and pregabalin are both incorrect because they’re newer antiepileptic agents. divalproex has a black box warning for liver failure and pancreatitis.
Pancreatitis is just inflammation of the pancreas, so both of them would present as but liver failure you could differentiate because that would present as jaundice which is orange-ing of the skin. high ammonia, that would that just happens because of a buildup of ammonia in the brain, and that would present as carbamazepine and divalproex both have the narrow therapeutic
Index, but they don’t undergo saturable kinetics. d) and e) are incorrect, gabapentin and pregabalin, because there are newer anti-epileptics. narrow therapeutic index just means the small differences in therapeutic failure or toxicity. basically, the differences in the dose can lead to different blood concentrations and instead of the drug work in in its window of where
It works correctly, it can tip it really easily into either not working at all which would not control seizures or having toxicity which would lead to some some pretty nasty side effects. with most drugs, whenever we give a dose, the dose given is directly related to our blood levels. if we increase the dose, we will increase blood levels exponentially with phenytoin –
It has nonlinear kinetics, so small changes in dose can lead to exponentially higher levels in the body, so we just need to monitor this more cautiously. especially with patient preference if they don’t want to come in and get their blood drawn often and undergo a lot of monitoring of this medication, then this one might not be the one for them, although it’s it’s been
Around the longest and it’s pretty reliable. carbamazepine, divalproex and phenytoin are incorrect because they’re older anti-epileptics. and so gabapentin and pregabalin are both correct. we see these a lot more for neuropathy and not quite as much for seizures. like we discussed earlier, the newer anti-epileptics are still kind of finding their way into an interesting
Fact about a lot of the newer anti-epileptics – most of them, when they were studied, which we’ve already used for a long time, and so we were not really sure how these medications will work if they do or if they’re able to work by themselves, so that’s kind of why they’re they’re not quite the front-runner in seizures, especially these two since we just mostly see them
Being used for neuropathy or nerve pain.
Transcribed from video
(CC) Antiepileptics Phenytoin vs Carbamazepine (CH 5 NEURO NAPLEX / NCLEX PHARMACOLOGY REVIEW) By Tony PharmD
