Antidepressant Toxicology Flashcards
What type of drug is doxepin?
TCA
What causes the increase risk of seizures with TCA overdose?
Decreased Cl flow through the GABA mediated Cl channels
Why can there be intermittent periods of intoxication and recovery with TCA overdoses?
Anticholinergic effects on the gut will slow motility/absorption, until effect wears off.
What is the effect of acidosis on TCA intoxication? (2)
- Increases the amount of non-protein bound drug
- Increases Na channel blocking effect
What is the role of dialysis in TCA overdose and why?
Not effective, since highly protein bound
Which leads on an EKG will better reflect the changes with TCA overdose? What pattern does is resemble?
Limb leads
RBBB
What causes the hypotension with TCA overdose?
- Peripheral alpha blockade
- Decreased ionotropy
Which TCAs in particular predispose to seizures?
Amoxepine
Maprotiline
What meds are NOT used to treat seizures 2/2 TCA overdose?
Phenytoin (worsens Na channel blockade)
What happens if a cholinergic drug is given to combat the anticholinergic effects of TCAs?
Worsens cardiac issues
How does alkalinization work in the treatment of TCA overdose?
Increases TCA binding to proteins and frees heart from Na channel blockade
What is the antiarrhythmic of choice for TCA overdose?
Lidocaine
How long must patients be monitored for with TCA overdose?
24 hours
What are the two hydrazine derivative MAOIs? What is the significance of this?
- Isocarboxazid, Phenelzine
- inhibit Vitamin B6 production, leading to seizures
what is the difference between drug half-life and physiologic effect half-life of MAOIs?
Drug half life is short, but the physiologic effects are long
what is the enzyme that the hydrazine derivative MAOIs block to causes seizures? What metabolic change does this cause?
Pyridoxine phosphokinase.
Increases glutamate
Decreased GABA
What is the MOA of MAOI intoxication?
Inactivates neuron stored and neuron released catecholamines
What is the role of dialysis in MAOI intoxication and why?
No role
High protein binding
When is the latent period in MAOI overdose?
6-12 hours
What, generally, are the s/sx of MAOI overdose?
Sympathomimetic
What are the three poor prognostic indicators in MAOI overdose?
- hyperthermia
- hypotension
- (heart) ventricular arrhythmias
What is the antihypertensive of choice for MAOI overdose?
Nitroprusside
What is the treatment for hyperthermia associated with MAOI overdose?
Cooling, benzos
When do s/sx appear of the Tyramine reaction with MAOI overdose?
minutes to few hours
