Flashcards in Active Learning DRUGS Deck (16):
What are the therapeutic usage of Phenytoin?
Generalized tonic clonic seizures, status epilepticus, partial, complex and focal
What are the pharmacokinetics of phenytoin?
given oral - complete absorption through GI
IM - not reccommended
take with food to avoid side effects
CSF - concentration is proprotional to free plasma level
Metabolized to inactive form in liver, excreted in urine
What are the side effects of phenytoin?
Dose-related adverse effects:
-nystagmus and ataxia
-sedation at higher levels
-inducer of drug metabolism (other drugs broken down more quickly)
Drug interactions involving phenytoin are primarily related to protein binding or to metabolism. Since phenytoin is 90% bound to plasma proteins, other highly bound drugs can displace phenytoin from its binding site.
Mechanism of action of phenytoin?
Prolongs the inactivation phase of the v-gated sodium channels
-This prevents rapid-firing of Action potentials
It also MIGHT inhibit glutamte and promote GABA release (by another mechanism)
What drug other than phenytoin is also a strong inducer of hepatic enzymes?
(Watch out, it could reduce the effectiveness of other seizure meds or contraceptive pills!)
What are the uses of carbamezepine?
drug of choice for focal, tonic/clonic, and partial complex seizures.
Side effects of carbamezepine?
-Luekopenia and Hyponatremia
-High for asian patients with HLA-B-1502 allele
What is the primary treatment for absence seizures?
(not effective for convulsive)
Mechanism of Ethnosuximide?
Mech: Reduces low threshold Ca currents in the thalamus
Adverse: Behavioral changes, Lupus
Valproic acid works for what kinds of seizures?
Works for: Most types of seizure
Mech: Inhibits Na channels to stop rapid firing AND stops Ca currents
Why would it not be good to mix Valproic acid and phenytoin?
Valproate inhibits metabolism of phenytoin and other drugs that are substrates of CYP
Valproate is also bound to albumin and displaced the phenytoin that would normally bind there too.
Adverse effects of Valproic Acid?
Alopecia, weight gain.
(sounds sort of Homer Simpson-esque...)
Any drug interactions with Levetiracetam?
Adv effects: behavioral changes
Mechanism of Topirimate?
Reduces V-gated Na currents in cerebellar cells AND activates a hyperpolarizing K current AND enhances some GABA currents too
(word-finding, concentration, memory impairment)
Remember: Topamax = Dopamax!
What do you use Tiagabine for?
Mech of action?
Adjunct therapy for partial focal seizures
Inhibits GABA transporter GAT-1