Mood stabilizers and antiepileptics Flashcards Preview

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Flashcards in Mood stabilizers and antiepileptics Deck (19)
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1
Q

What is the gold standard of Bipolar and how does it work?

A
  • Lithium
  • May inhibit second messenger system from neurotransmitter receptors
    • competes with Na, Ca, Mg, affecting cell membranes, H2O and neurotransmitters
  • Not understood well, but niether is bipolar disease
2
Q

Lithium

Pharmacokinetics

A
  • Distributed through total body water and excreted by the kidneys
  • filtered by glomerulus and reabsorbed by proximal tubule
    • reabsorption is competitive with NA, so if Na level is low, may have increased plasma level concentration of lithium up to 50%
  • E1/2t is 24 hrs
3
Q

How long does it take to become steady state with Lithium?

What is the therapeutic range?

A
  • Steady state is 4-5 elimination 1/2 times
  • therapeutic range 1.0-1.2 mEq/L
4
Q

Lithium

side effects

A
  • Kidneys
    • evaluate renal function every 6 months
    • polydipsia and polyuria; >3L/day
    • impaired renal concentrating
    • Amiloride (potassium sparing diuretic) can decrease urine volume
  • EKG
    • T-wave changes, flattening or inversion
    • reversible
  • Heart block (rare)
    • contraindicated in pts with SA node dysfunction
  • hypothyroidism
  • psoriasis
  • hand tremor
  • sedation
  • memory disturbances
5
Q

What are the symptoms of mild Lithium toxicity?

A
  • Mild
    • sedation
    • nausea
    • skeletal muscle weakness
    • wide QRS
    • AV heart block
    • hypotesion
    • dysrhythmia
    • sz
      *
6
Q

What is considered significant toxicity?

A
  • plasma level > 2.5 mEq/L
  • this is a medical emergency
  • requires aggressive treatment
  • hemodialysis
  • osmotic diuresis and IV NA bicarb
7
Q

What are some anesthetic considerations for a pt on Lithium?

A
  • Preoperative labs and ECG
    • bun, cr
    • looking for T wave changes
  • Lithium has reactions with many drugs
    • NSAIDS- avoid; especially ketoralac
    • can cause kidney problems
  • anesthetic requirements may be decreased
  • action of neuromuscular blocking agents may be prolonged
8
Q

What is the goal of antiepileptics?

A
  • to control seizures without medication related side effects
  • achieved in 70% of patients with only one antiepileptic drug
  • drug of choice depends on type of seizure
9
Q

MOA of antiepileptic drugs

A
  • decrease neuronal excitability or enhance inhibition of neurotransmission
  • achieve by altering intrinsic membrane ion currents
    • Na, K, Ca
  • enhancement of GABA action
10
Q

How are lab tests used regarding antiepileptics?

A
  • routine monitoring of plasma concentration used to guide dose adjustments
  • “therapeutic ranges” do not often correspond to individual responses
    • titrate to clinical efficacy
  • check plasma levels to determine compliance with treatment and pharmacokinetic interactions
  • Check for liver function-
    • before starting treatment b/c they are hepatotoxic
  • hematologic
    • life threatening bone marrow suppression
11
Q

What else are antiepileptics being used to treat?

A

bi-polar disorder

Carbamazepine (Tegretol)

Valproate (depakote)

lamictal

12
Q

What is the prototype of antiepileptics?

what is it used for?

MOA?

A
  • Phenytoin
  • effective to treat partial and generalized seizures
    • can be given IV or PO
  • MOA
    • regulates neuronal excitability, and thereby the spread of seizure activity from a seizure focus, by regulating Na and Ca ion transport across neuronal membranes
13
Q

What is the pH of Phenytoin ?

Can you give it IM?

How fast can you infuse?

A
  • pH of 12, precipitates in solutions with pH <7.8
    • only mix with saline
  • NOt recommended for IM injections because it precipitates at the sight and is poorly absorbed
  • Infuse no faster than 50 mg/min in adults
    • 1-3 mg/kg/min in peds or 50 mg/min, whichever is slower
    • too fast will cause arrhythmias and possible cardiac arrest
14
Q

Phenytoin pharmacokinetics

A
  • poorly H20 soluble, variable absorption from GI tract
  • highly protein bound- 90% to albumin
15
Q

How is pheynytoin metabolised?

A
  • by hepatic microsomal enzymes
  • inactive metabolites
  • plasma concentration
    • <10 mcg/ml first order kinetics
    • >10 mcg/ml zero order kinetics
16
Q

Phenytoin side effects

A
  • CNS toxicity
    • nystagmus, ataxia, diplopia, vertigo
    • peripheral neuropathy
  • acne
  • facial coarsening
  • allergic rash; stevens Johnson syndrome
  • GI irritation
  • hepatotoxicity
  • induces hepatic enzyme system
17
Q

Fosphenytoin

Where does it act?

pharmacokinetics

use?

loading dose

A
  • acts on Na ion channel blockade
  • highly pb
  • water soluble phenytoin pro drug
  • used in hospitals for status epilepticus and in neurosurg to prevent/treat sz
  • 10-20 mg/kg IV loading dose
18
Q

Phenobarbital

What is it?

Side effects?

A
  • long acting barbiturate
  • side effects
    • cognitive and behavioral side effects limit usefulness
    • sedation in adults; hyperactivity in children
    • depression
    • confusion in elderly
19
Q

Phenobarbital MOA

A
  • MOA
    • modulation of post synaptic actions of GABA and glutamate
    • prolongs duration of chloride channel opening, limiting spread of sz
  • Metab
    • enhances CYP450