Mood stabilizers and antiepileptics Flashcards
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
