Toxicology and Poisoning Flashcards
What are the pharmacokinetic interventions available for overdose treatment/poisoning to prevent absorption?
1) Emesis
2) Gastric lavage
3) Chemical adsorption
4) Osmotic cathartics
Describe emesis. What are examples of emetic agents?
Emesis empties stomach contents rapidly
1) ipecac
2) apomorphine
What are the contraindications of using an emetic agent?
1) Comatose pt (no gag reflex –> risk of aspiration)
2) ingestion of corrosive poisons
3) ingestion of CNS stimulant (risk of seizures)
4) ingestion of petroleum distillate (problem if pregnant)
What is ipecac?
Causes emesis after 15-30 min lag — may repeat once every 20 min
Causes local irritation and CNS stimulation of chemoreceptor trigger zone (CTZ)
Given orally
What is apomorphine?
A dopamine agonist — rapid action given by injection
Causes emesis by stimulation of CTZ
Respiratory depressant, toxic in kids, rarely used today
Describe gastric lavage.
Most rapid and complete method of emptying stomach
Lavage + emesis –> only empties 30% of oral poisons
Wash stomach with saline and removal via nasogastric tube — best w/in 60 min
Describe chemical adsorption.
AKA: activated charcoal
Binds drug in gut to limit absorption (also binds ipecac)
Effective prior to gastric lavage
Can reduce elimination half-lives
Describe osmotic cathartics
Decrease time of toxin in GI tract (osmotic laxative effect)
Needed if toxin ingested >60 mins, enteric coated tablets ingested, or hydrocarbon ingested
What are 4 types of osmotic cathartics?
1) Sorbitol 70%
2) Magnesium citrate/sulfate
3) Sodium sulfate
4) Polyethylene glycol
Describe sorbitol 70%
Recommended osmotic cathartic
Given with charcoal to prevent “charcoal briquet” formation
Describe magnesium citrate/sulfate
A osmotic cathartic
Avoid in renal disease or poisonings with nephrotoxic agents
Describe sodium sulfate
A osmotic cathartic
Avoid in CHF or HTN (system absorption –> fluid overload)
Describe polyethylene glycol
A osmotic cathartic
Whole bowel irrigation that promotes elimination of entire intestine contents
For poisonings with sustained-release drugs, metal ions, drug packets
What are the pharmacokinetic interventions available for overdose treatment/poisoning to enhance elimination?
1) Extracorporeal removal
2) Enhanced metabolism
3) Enhanced renal excretion
4) Chelation of heavy metals
Describe extracorporeal removal. Name 2 types.
Yield lots of complications, only give if the pt really needs this
1) Hemodialysis/ peritoneal dialysis
2) Hemoperfusion
Describe hemodialysis/peritoneal dialysis
Blood pumped through filter — most effective for drugs with small Vd (large Vd —> outside plasma)
Toxin should have low protein binding capacity (won’t cross membrane otherwise)
Corrects electrolyte/fluid imbalance
Describe hemoperfusion
Blood pumped through column of adsorbent material — useful for high MW toxins w/ poor water solubility
Risks: bleeding and electrolyte disturbances
Describe enhanced metabolism
- Enhancement of detox metabolic pathways with N-acetylcysteine (tylenol toxicity)
- Induction of CYP450 not realistic due to delay (1-3 days for onset)
- Inhibition of metabolism to block toxic metabolite formation has been successful (ethanol)
Describe enhanced renal excretion. Name 2 types.
Previously popular but of unproved value
1) Forced diuresis
2) Block reabsorption from kidney
Describe forced diuresis, including its pros and cons.
- A type of enhanced renal excretion
- fluids + high efficacy diuretics
- PROS: protects kidneys
- CONS: small effect with fluid overload danger
Describe process of blocking reabsorption from kidney
- A type of enhanced renal excretion
- prevents passive reabsorption by altering urine pH and ion trapping
- For weak toxic base: acidify urine with NH4Cl/ascorbic acid
- For acidic: alkalinize urine with NaHCO3