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2013-04-15 20:27:20
Pharm 4B

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  1. AEDs major mechanisms (4)
    1. inhibition of Na+ channels in neuronal membrane

    2. inhibition of Ca++ channels

    3. enhanced GABA neurotransmission or decreased degradation of GABA

    4. Glutamate receptor antagonists
  2. Almost all antiepeleptic drugs are associatied with what?
    CNS depressing effects

    -some tolerance to these effects develops over 7-10 days
  3. Carbamazepine (Tegretol)
    -Pharm: metabolized by CYP 3A4; autoinduction (drug interactions are common - need dose increase); category D

    -Use: partial seizures esp. complex partial, tonic clonic generalized sz; mood stabilizer in BPD
  4. Carbamazepine AE and DI
    • AE:
    • -black box warning: frequent CBC monitoring secondary to few cases of aplastic anemia and leukopenia (10%)

    -rash: SJS and TEN-in initial 2 months; check for HLA-B allele in asians

    • DI:
    • -Erithromycin and clarithromycin
    • -increased metabolism of valproic acid, theophylline, and warfarin
    • -serum drug levels
  5. Oxycarbazepine (Trileptal)
    New AED

    -more expensive but better tolerated

    -no autoinduction

    -potential 1st line drug for partial and general tonic clonic seizures; role as mood stabilizer for bipolar
  6. Phenytoin (Dilantin)
    AED of choice for generalized type tonic clonic seizures; status epilepticus, prophylaxis and treatment of seizures in neurosurgery

    -MOA: alters Ca++ uptake, alters Na/K+ pump, slows rate of Na+ channels recovery

    • Pharm:
    • -liver metabolism via CYP 2C9 and inducer of 3A4

    -IV fosphenytoin (loading dose then maintenance)

    -Loading dose and half life: 400, 300, 300

    -irritating to veins and tissue
  7. Phenytoin (Dilantin) AE (6) and DI (2)
    • AE:
    • 1. lethargy, fatigue
    • 2. drowsiness, ataxia
    • 3. nystagmus > 20mcg/ml
    • 4. IV effects -- hypotension
    • 5. gingival hyperplasia (50%)
    • 6. chronic effects: endocrine and metabolic

    • DI:
    • -other AEDS
    • -pregnancy cat D
  8. Valproic acid (Depakene)
    Diverse AED 1st line for generalized absence and myclonic siezures 

    -MOA: affects Na+ channels (prolong inactivation) AND MAY affect GABA metabolism (increased brain levels)

    • Pharm:
    • -liver metabolism and renal excretion
    • -comes in entericcoated, caps, tabs, syrup
  9. Valproic acid AE and DI
    • AE:
    • -most common: dizzy, tremor, HA, insomnia, blurred vision, diplopia
    • -most serious is hepatotoxicity early in the coarse = BB warning

    • DI:
    • -Other AEDs
    • -pregnancy category D
  10. Phenobarbital and Primidone
    Oldest AED

    -MOA: barbiturate bind to receptors, which enhance inhibitory effects of GABA on postsynaptic neurons

    -Pharm: IV>IM>PO; P450 inducer

    • Uses:
    • -neonatal seizures (1st line)
    • -generalized tonic clonic seizures
    • -may be useful for partial seizures
  11. Phenobarbital AE (4)
    • 1. CNS depressant effects (drowsy)
    • 2. impairs cognitive function and may paradoxically stimulate children
    • 3. rashes
    • 4. PB is enzyme inducer and may increase elimination of drugs metabolized by hapatic enzymes
  12. Topiramate (Topamax)
    MOA: multiple actions

    • Pharm:
    • -caps (sprinkle for children), tabs
    • -renal excretion

    • AE:
    • -ataxia, memory impairment, parasthesia
    • -weight loss!! anorexia and nausea
    • -nephrolithiasis so drink lots of water
    • -fewer DI than other AEDs
  13. Ethosuxmide (Zarontin)
    -MOA: reduces Ca++ currents in thalamic neurons; suppresses certain sz patterns in motor cortex and basal ganglia

    -Pharm: (caps, syrup) rapid GI absorption, liver metabolism, mostly renal excretion

    -Uses: first line for absence seizures; may be used alone or in combo w/ valproic acid
  14. Ethosuximide AE (5)
    • 1. well-tolerated
    • 2. N/V and anorexia are common
    • 3. drowsiness, fatigue, lethary
    • 4. rarely rash, hypersensitivity rxns
    • 5. qd or BID/tid dosing depending on GI effects
  15. Lamotrigine (Lamictal)
    New AED

    -MOA: unknown, may be Na+ and Ca++ channels in neuronal membranes

    -pharm: orally tabs and chewables

    -use: adjunctive and monotherapy for partial epilepsy refractory to other agents
  16. Lamotrigine AE (4) and DI (2)
    • 1. diplopia, HA, and ataxia are M/C
    • 2. GI upset
    • 3. BB warning = rash which appears in first 3-4 weeks and may require withdrawal (rarely SJS or TEN)

    • DI
    • -if using inducers, may need to increase lamotrigine dose
    • -valproic acid use increases risk of rash although often used together (use lower dose)
  17. Gabapentin (Neurontin)
    New AED

    -MOA: Enhances GABA neurotransmission and may modulate Ca++ channels

    -Pharm: PO dosing (caps, tabs, oral solution)

    -Use: monotherapy and adjunctive therapy of partial seizures; neuropathic pain, Bipolar
  18. Gabapentin AE (7)
    • 1. Category C
    • 2. fatigue, dizziness, ataxia
    • 3. tremor and nystagmus
    • 4. weight gain and edema
    • 5. better tolerated overall
    • 6. no major DI
    • 7. frequent daily dosing (TID)
  19. Levetiracetam
    New AED

    -used as adjunctive for partial sz in adults; primary generalized tonic-clonic sz in adults and children >=6 w/ idiopathic generalized epilepsy

    -AE: well-tolerated; asthenia, somnolence dizziness
  20. Tiagabine
    -AE (2)
    New AED

    -MOA: inhibits GABA reuptake into neurons and glial cells

    -Use: adjunctive for partial seizures with other drugs

    • AE:
    • 1. dizzines, tremor, and somnolence
    • 2. may increase absense seizures
  21. Zonisamide (Zonegran)
    -AE (2)
    New AED

    -used as adjunct for partial seizures

    • -AE:
    • 1. ataxia, anorexia, somnolence, nervousness
    • 2. renal calculi in 1%
  22. Pregabalin, Lyrica
    -Use (3)
    -AE (3)
    • -Use:
    • 1. adjunctive use for partial seizures
    • 2. fibromyalgia
    • 3. neuropathic pain (DM and postherpetic neuralgia)

    • -AE:
    • 1. dose-dependent
    • 2. dizziness, somnolence, dry mouth, edema,  blurred vision, weight gain
    • 3. "thinking abnormal" (primarily difficulty with concentration/attention
  23. Rufinamide (Banzel)
    • NEW AED
    • -modulation of the activity of sodium channels and, in particular, prolongation of the inactive state of the channel

    -Use: adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in children 4 years and older and adults

    -AE: QT shortens, ataxia, dizziness, nausea
  24. Lacosamide (Vimpat)

    -IV, PO Tx of partial seizures

    -PR prolongation, dizzy, ataxia, N/V, vertigo, blurry vision

    -Na+ channel inactivation

    -Category C
  25. Potiga (Ezogabine)
    -MOA: open K+ channels and reduces neuronal excitability

    -Use: adjunctive tx of partial seizures; the usual initial dose of Potiga is 100mg PO 3 times daily

    -AE: dizziness, vertigo, sleepiness, fatigue, problems w/ gait or coordination, confusion, memory problems, tremor