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13 Cards in this Set

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  • Back
What are the drugs that block sustained repetitive firing of Na APs?
Phenytoin, carbamazepine and lamotrigine
What is the mechanism of Phenytoin>?
*molecules in extracellular space in resting state, but enter the Na+ channel when it opens and bind to the inactivation particle of the channel in the intracellular space-prolong their inactivation and delya the recovery and stop repetitive firing
What are the pharmacokinetic properties of phenytoin?
*water insoluble at neutral PH and IV would cause muscle necrosis so use IV Phosphenytoin =prodrug water soluble.
**Oral absorption solw and variable
*Elim: hepatic metabolims cyto P450; non-linear kinetics; dec. clearance with inc. conc.
*must moniter levels
variation in half per person
What are the toxicities of phenytoin>?
ataxia, nystagmuc (horiz), lethargy
Idiosyncratic: first 3 mos; Rashes, Steven Johnson syndrome, heptaitis and LAD
What are the SE of chronic administration of phenytin?
ginigival hyperplasia, coarsening of facial features, hirsutism
Some pts: cerebellar atropy, peripheral neuropathy, cognitive effects, accelerates metabolism of vit D and K=> osteoperosis or hypoPT in infants with moms on it
What are the teratogenic effects of phenytoin/
inc. risk of fetal malformations of all types; cleft lip/palate, cardiac; inc. incidence of malformation in mothers taking other anticonvulsants as well; all females should be on folate with an anticonvulsant
What are the drug interactions of phenytoin?
induction or inhibition of heptaic metabolism or competition for plasma protein binding
What are the therapeutic uses of phenytoin?
1. Until recently most widely used anticonvulsant; simple partial, complex partial, and primary and secondarily generalized tonic-clonic seizures and primarliy generalized tonic clonic seizures
What is Carbamazepine?
Structurally related to TCAs, anticonvulsant with similar mechanism ot phenytoin.
What are the pharm properties of Carbamazepine?
Oral Only.
*Met by liver to one active metabolite; 1st order kinetics
*induces its own metabolism over 2-4 wks, start slow and work up to optimal doese.
WHat are the contraindicated drugs of carbamazepine?
erytromycin and cimetidine, calcium channel blockers because they inhibit metabolism
What are the toxic effects of carbamazepine?
dizziness, drowsiness, diploplia, sedation
1. Leukopenia: transient and mild, can be more perisitant and sever=rare
2. Aplastic anemia: rare and unpredicatable
What are the therapeutic indications for carbamazepine?
1.First line drugs for partial seizrues, esp. in kids.
Most widely RX for these.
2. Primary agent for trigeminal and glossopharyngeal neuralgia
3. bipolar disorder and useful in pts with epilepsy who are depressed