Toxicology Flashcards
Which drug is one of the more common causes of intentional oversdose because of accessibility?
Tylenol
Which drug can lead to acute hepatic failure that needs immediate intervention in an overdose?
Tylenol
What is the lethal dose of Tylenol?
10 g when acutely ingested
How long does it take for acute hepatic failure to take place in a Tylenol OD?
A day or 2
What is the maximum daily recommended dose of Tylenol?
3000mg
Tylenol metabolism (OD) in the body and how is this dangerous?
90% of the drug gets inactivated and a small percentage gets converted into NAPQI, which is a toxic metabolite that affects the liver.
When you take large amounts of it, your body can’t break it down anymore and you start to accumulate it, which leads to liver failure
What is responsible for APAP (Tylenol) metabolism that prevents toxic acuumulation of NAPQI?
Glutathione, this is hepatoprotective
Reasons you can get hepatic depletion of glutathione?
Chronic ETOH, APAP use or cirrhosis
How might a chronic APAP use present vs actue?
Chronic is more often asymptomatic and may present as a “viral syndrome”
Acute usually starts with emesis with possibly RUQ pain within 48-96 hrs, and can present as hypotensive, encephalopathy, elevations of AST/ALT and coagulopathies
How might labs present in chronic APAP use?
could be high-normal, but are mostly normal
What are good liver markers to check for in the lab?
AST/ALT, INR, Alkaline phosphatase
What do salicylate levels indicate?
ASA use
With acute APAP toxicity, what is a good lab work up?
CMP, Acetaminophen level, salicylate level, ETOH level, INR/PT
The Rumack-Matthew Nomogram is used for what?
Acute ingestion of alcohol
When can you get a Acetaminophen level?
Starting 4 hrs post ingestion
What’s makes diagnoses difficult with overdoses?
Many drugs or drug combos are often used
What is the treatment for APAP OD?
NAC (N-Acetylcysteine, Acetadote)
What does NAC do?
Replenishes glutathiones stores, which helps metabolize NAPQI
Which administration method is prefered for NAC? Why?
IV, because PO smells like rotten eggs
What can we give for massive APAP ODs?
Hemodialysis
And if it’s within an hour since ingestion, activated charcoal (but it’s not often well tolerated)
APAP OD can also cause what?
Cerebral edema, seizures
ASA toxicity can caue you to what?
Bleed
Early S/S for ASA OD? (like 1-2 hrs) Which is often the biggest clue for dx?
Tinnitus, vertigo, N/V/D, tachypnea
**Tachypnea
What happens, pathophysiologically, in an ASA OD?
You ingest a lot of acid, your body compensates via becomine tachypneic to raise CO2 levels. The patient first undergoes respiratory alkalosis. Then, the pH starts to rise and bicarb drops, becoming metabolic acidosis
Fever can occur in which kind of OD?
ASA
What ultimately causes the metabolic acidosis disturbance in ASA OD?
Anion-gap
The acidity of the metabolic acidosis via ASA OD can cause what?
AMS, CV collapse, death
Labs for ASA OD?
CMP, Lactate, coag panels, Salicylate level, APAP level, ETOH level
ASA Treatment?
If within 1-2 hrs of ingestion, you can do activated charcoal
Aggressive volume resuscitation, urine alkalinization (sodium bicarb IV bolus and infusion to increase ASA excretion), hemodialysis
Which 2 drugs present similarly in OD?
CCB and BB
Which CCBs cause more AV nodal blockades?
Non-DHP
AV nodal action can cause what?
profound hypotension and bradycardia
DHPs can present with what?
Profound hypotension (due to peripheral vasodilation) WITHOUT direct myocardial effects
In what case could the DHP CCB and the Non-DHP CCB present similar in their OD?
With large OD
Which meds have a long half life that can make OD treatment difficult?
CCB (24 hrs, which means it would take 4-5 days to get out of your system)
Main difference in the OD presenting symptoms of CCBs and BBs?
HYPERglycemia in CCBs
HYPOglycemia in BBs
CCBs prevent beta islet cells from insulin release
AMS is more common in BBs
Presenting symptoms in Non-DHP CCB OD?
Hypotension, Bradycardia, CHF symptoms
Lab tests for CCB OD
EKG, CMP, Glucose, APAP, Salicylate, ETOH levels
Treatment for CCB OD?
Atropine (for the bradycardic symptoms)
Usually we’ll have to do more, so we add:
IV calcium (helps antagone effects of CCB, but doesn’t alter intracellular dysfunction of calcium)
IV glucagon (assist more with HR) premedicate with anti-emetics for this, though
IV insulin (HIGH dose, 10xs more than what we use for DKA) to help with vasopression and overcome insulin resistance in CCB OD
IV Vasopressors (epinephrine, vasopressin, norepiniphrine)
Fun fact? What can you also use to induce vomiting in people who have food stuck in their throat?
IV glucagon
What do Beta 1 receptors do?
They increase RH and contractility
What do Beta 2 receptors do?
Vasodilation and bronchodilation
How long do you see PK changes in BB OD?
2-8 hrs
Which Beta blockers can cause ventricular arrhythmias?
Sotalol, Acebutolol, propranolol
Which beta blocker is lipophilic and can easily cross the BBB? What are its side effects?
Propranolol
SE: increased CNS SE, seizures
Which Beta blockers block alpha receptors?
Carvedilol, labetalol
Treatment for BB OD?
IV atropine, glucagon, insulin with dextrose (watch out for hypoglycemia, need more dextrose infusions), calcium, vasopressors, bensodiazepines, lipids (indicated for refractory seizure, CV collapse due to propranolol OD)
What happens in serotonin syndrome?
overstimulation of serotonergic receptors in the CNS and periphery
What does serotonin do?
attention, behavior, thermoregulation
What age groups has serotonin syndrome been documented in?
All age groups
How can serotonin syndrome be diagnosed?
NOT by labs, it’s a dx of exclusion
Hunter criteria is used when pt has taken a serotonergic product and has one of:
spontaneous clonus, inducible clonus and agitation/diaphoresis, ocular clonus and agitation/diaphoresis, tremor and hyperreflexia, hyperonia, temp over 100.4F and ocular/inducible clonus
Differential dx for serotonin syndrome?
MH and NMS, and anticholinergic toxicity
What can cause serotonin syndrome?
Analgesics (codeine, fentanyl, meperidine, tramadol)
Antibiotics (linezolid)
Antidepressants (SSRIs, SNRIs, TCAs, MAOIs)
Triptans
Herbals (St. John’s Wort, Panax ginseng, tryptophan)
Illicit drugs (Amphetamines, cocaine, ecstasy, LSD)
Dextromethorphan, lithium, methylene blue
How do you treate serotonin syndrome?
Stop offending agents, stabilize vitals, benzos for agitation
+ cyproheptadine (12 mg inititally PO then 2mg q2hrs until clinical response)
+esmolol/nitroprusside for severe HTN; sedation and paralysis with non-depolarizing agent with intubation
What antihistamine has anti-serotonergic activity that is used to treat serotonin syndrome?
Cyproheptadine
Indications for cyproheptadine?
serotonin syndrome, appetite stimulation, spinal cord injury (spasticity)
S/S Neuroleptic malignant syndrome
AMS (most often the first sign), rigidity, fever, autonomic instability
Lab results on NMS
SCK >1000 Leukocytosis mild elevations in LDH, AlkPhos, AST/ALT Electrolytes - HypoCa, HypoMg, *HyperK, metabolic acidosis Elevated SCr (rhabdomyolysis)
*most concerning
What drugs can cause NMS?
Often with haloperidol, fluphenazine (but really any antipsychotic), metoclopramide, promethazine, withdrawal of carbidopa/levodopa
treatment for NMS
stop drugs, cooling blankets, anticoagulation, ABCs, fluids
Drug of choice for MH?
Dantrolene (Ryanodex)
What is the mechanism from dantrolene?
direct-acting skeletal muscle relaxant that inhibits ryanodine receptors to prevent Ca2+ release from sarcoplasmic reticulum
Reduces temp and muscle rigidity
Dantrolene use
Max of 10 day therapy (but usually stopped within a couple of days)
SE for dantrolene
hepatotoxicity
What is MH?
genetically-linked hypermetabolic state that is life-threatening; usually occurs in those who have taken halothane, isoflurane, enflurane, sevoflurane, or succinylcholine
S/S of MH
rise in end-tidal CO2 despite increase in minute ventilation, muscle rigidity? (pts are usually sedated, so hard to know), hypertermia (late-stage), sinus tachycardia
Post crisis protocol for MH?
Dantrolene 1mg/kg q4-6 hrs
OR 0.25mg/kg/hr continusou infustion for at least 24 hrs