ABP Med Toxicology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Therapeutic index

Therapeutic index is the ratio of the toxic dose to the effective dose in 50% of subjects (TD50/ED50); a larger index generally indicates a wider margin between benefit and toxicity.

NOAEL

No-observed-adverse-effect level is the highest tested dose producing no statistically or biologically significant adverse effect; it is used to derive reference doses by applying uncertainty factors.

Risk assessment steps

Hazard identification, dose-response assessment, exposure assessment, and risk characterization; these four steps combine toxicity data with estimated human exposure to estimate the likelihood and severity of harm.

Volume of distribution

Apparent volume of distribution (Vd) equals the total body burden of drug divided by its plasma concentration; a large Vd indicates extensive tissue distribution and limits removal by hemodialysis.

Osmolal gap

Serum osmolal gap is measured osmolality minus calculated osmolality (2 x Na + glucose/18 + BUN/2.8); an elevated gap suggests unmeasured osmoles such as methanol, ethylene glycol, or isopropanol.

First-order elimination

In first-order kinetics a constant fraction of drug is eliminated per unit time; half-life is 0.693 x Vd/CL and steady state is reached after about four to five half-lives.

Zero-order kinetics

Zero-order elimination removes a constant amount of drug per unit time because metabolic pathways are saturated; ethanol, phenytoin, and high-dose salicylates show this pattern, so small dose increases can raise levels disproportionately.

Acetaminophen antidote

N-acetylcysteine replenishes glutathione and detoxifies NAPQI; it is most effective within 8 hours of ingestion, and treatment decisions often use the Rumack-Matthew nomogram at 4 hours.

Salicylate toxicity signs

Salicylism causes tinnitus, vomiting, hyperventilation, respiratory alkalosis, and metabolic acidosis; severe cases develop seizures, coma, pulmonary edema, and hypoglycemia, and urine alkalinization enhances elimination.

Digoxin toxicity antidote

Digoxin-specific Fab fragments bind digoxin and reverse life-threatening arrhythmias and hyperkalemia; calcium administration is traditionally avoided because of concern for worse dysrhythmias.

Tricyclic overdose effect

Tricyclic antidepressants block sodium channels, causing QRS widening, ventricular arrhythmias, hypotension, and seizures; sodium bicarbonate is the first-line treatment for cardiotoxicity.

Alcohol withdrawal timeline

Alcohol withdrawal begins with tremor and autonomic hyperactivity within 6 to 24 hours, seizures may occur at 12 to 48 hours, and delirium tremens typically appears at 48 to 96 hours.

Opioid withdrawal features

Opioid withdrawal causes yawning, lacrimation, rhinorrhea, piloerection, cramps, vomiting, and diarrhea; it is intensely uncomfortable but generally not life-threatening, and clonidine or buprenorphine can reduce symptoms.

Cocaine toxicity

Cocaine is a sympathomimetic that can cause hypertension, myocardial infarction, seizures, hyperthermia, and agitation; benzodiazepines are first-line for agitation and seizures, with supportive care for cardiovascular complications.

Carbon monoxide treatment

Carbon monoxide binds hemoglobin with high affinity; treatment is 100% oxygen, and hyperbaric oxygen is considered for severe poisoning, syncope, neurologic deficits, or pregnancy with significant exposure.

Caustic ingestion management

Acid and alkali ingestions cause chemical burns; do not induce vomiting or give activated charcoal, and perform early endoscopy in significant exposures to assess esophageal injury.

Cyanide antidote

Hydroxocobalamin binds cyanide to form cyanocobalamin and is preferred in smoke inhalation because it does not cause methemoglobinemia; sodium thiosulfate and nitrites are alternative antidotes.

Organophosphate poisoning

Organophosphates inhibit acetylcholinesterase, causing cholinergic excess with salivation, lacrimation, urination, diarrhea, bronchorrhea, bradycardia, and fasciculations; atropine treats muscarinic effects and pralidoxime can reactivate the enzyme.

Lead chelation

Severe lead poisoning with encephalopathy is treated with dimercaprol plus calcium disodium EDTA; oral succimer is used for moderate elevations, and removal from exposure is always required.

Iron poisoning antidote

Deferoxamine chelates free iron and is indicated for serious iron poisoning with shock, metabolic acidosis, or high serum iron; it may cause hypotension and should be guided by clinical severity.

Methylmercury toxicity

Methylmercury accumulates in fish and causes paresthesias, ataxia, visual field constriction, and developmental neurotoxicity; chelation is not routinely effective after established organic mercury exposure.

Amanita phalloides toxin

Amanita phalloides contains amatoxins that inhibit RNA polymerase and cause delayed severe gastroenteritis followed by hepatic failure; treatment includes supportive care, silibinin or N-acetylcysteine, and consideration of liver transplantation.

Ciguatera poisoning

Ciguatera is caused by reef fish toxins that activate sodium channels, producing gastrointestinal symptoms followed by paradoxical temperature reversal, paresthesias, and sometimes bradycardia or hypotension.

Scombroid poisoning

Scombroid is histamine toxicity from improperly stored fish, causing flushing, urticaria, headache, and diarrhea soon after eating; antihistamines relieve symptoms and it is not a true allergy.

Activated charcoal use

Activated charcoal adsorbs many drugs and is most effective within one hour of ingestion; it is contraindicated for caustic ingestions, hydrocarbons with aspiration risk, ileus, and an unprotected airway.

Urinary alkalinization

Raising urine pH to about 7.5 to 8 increases elimination of weak acids such as salicylates and phenobarbital; monitor pH, potassium, and fluid status because alkalinization can cause hypokalemia.

Hemodialysis indications

Hemodialysis removes low-molecular-weight, water-soluble drugs with small volume of distribution and low protein binding; classic indications include methanol, ethylene glycol, lithium, salicylate, and theophylline poisoning.

Button battery ingestion

A button battery lodged in the esophagus can cause liquefactive necrosis within hours; it is an emergency requiring immediate referral and urgent endoscopic removal rather than observation at home.

Pediatric ingestion prevention

Child-resistant packaging, locked storage of medicines and household products, safe disposal, and poison center consultation reduce pediatric poisoning; one tablet of some drugs can be lethal to a toddler.

Pediatric acetaminophen dosing

Pediatric acetaminophen dosing is weight-based, commonly 10 to 15 mg/kg per dose every 4 to 6 hours, with a maximum daily dose; dosing errors from combination products are a common cause of toxicity.

Anticholinergic toxidrome

Anticholinergic toxicity causes dry skin, flushing, mydriasis, blurred vision, urinary retention, decreased bowel sounds, agitation, and delirium; physostigmine may be used in selected severe cases without conduction abnormalities.

Serotonin syndrome

Serotonin syndrome presents with mental status changes, autonomic hyperactivity, and neuromuscular excitation such as clonus and hyperreflexia; stop serotonergic drugs, give benzodiazepines, and use cyproheptadine in selected cases.