DABAT key terms

A calculated apparent volume relating the amount of drug in the body to its plasma concentration. A large Vd suggests extensive tissue uptake and limits the usefulness of hemodialysis for removal.

The volume of plasma from which a substance is completely removed per unit time. It determines the rate of elimination relative to concentration and governs steady-state levels during repeated exposure.

The time required for the plasma concentration of a substance to fall by half during first-order elimination. It depends on both volume of distribution and clearance and guides dosing intervals and observation periods.

Elimination in which a constant amount of substance is removed per unit time because metabolic pathways are saturated. Concentrations then rise disproportionately with dose, as seen with ethanol, salicylates, and phenytoin.

Presystemic biotransformation of an ingested substance by gut wall or liver before it reaches systemic circulation. It reduces oral bioavailability and can generate toxic metabolites, as with acetaminophen.

The fraction of an administered dose that reaches systemic circulation unchanged. It differs by route and formulation and influences both peak concentration and the onset of toxicity.

A saturable enzyme model in which elimination rate approaches a maximum velocity as substrate concentration rises. At high concentrations elimination becomes near zero-order, causing nonlinear accumulation.

Enzymatic conversion of a xenobiotic into more water-soluble products, usually by phase I oxidation, reduction, or hydrolysis followed by phase II conjugation. It generally aids excretion but can create reactive intermediates.

Metabolic conversion of a relatively inert parent compound into a reactive, toxic species. Examples include NAPQI from acetaminophen and acrolein from cyclophosphamide.

A superfamily of heme-containing monooxygenase enzymes that perform most phase I oxidative drug metabolism. Individual isoforms differ in substrate specificity and in susceptibility to induction or inhibition.

Increased synthesis or reduced degradation of metabolizing enzymes after repeated exposure, raising metabolic capacity over days to weeks. It can lower parent drug levels while increasing toxic metabolite formation.

Reduction of metabolic enzyme activity by a competing substrate, cofactor depletion, or direct inactivation. It can rapidly raise concentrations of co-administered substrates and precipitate toxicity.

The graded association between the amount of exposure and the magnitude or frequency of a biological effect. It underpins threshold concepts, potency comparisons, and regulatory limits.

The lowest dose at which an effect begins to appear in a population or individual. Below it, homeostatic and detoxifying mechanisms are assumed to prevent measurable harm.

No-observed-adverse-effect level: the highest tested dose producing no statistically or biologically significant adverse effect. It is commonly divided by uncertainty factors to derive acceptable exposure limits.

A modeled dose estimated to produce a specified small increase in response, often derived from all dose-response data with statistical confidence limits. It is an alternative to the NOAEL for risk assessment.

A numerical divisor applied to an experimental threshold to account for animal-to-human differences, human variability, and data gaps. The product of factors yields an exposure level presumed protective.

An estimate of daily oral exposure likely to be without appreciable risk of adverse effects over a lifetime. It is derived by dividing a NOAEL or benchmark dose by uncertainty factors.

The first risk assessment step, determining whether an agent has the inherent capacity to cause adverse effects. It draws on structure-activity data, animal studies, and human evidence.

The final risk assessment step integrating hazard identification, dose-response, and exposure assessment to estimate the likelihood and severity of harm in a defined population.

Quantification of the magnitude, frequency, duration, and route of contact between a population and an agent. It is combined with dose-response information to estimate risk.

Measurement of a substance, its metabolite, or a biological effect marker in body fluids or tissues to estimate absorbed dose. It captures all routes of exposure and individual variability.

A reference value for a biomarker measured in a biological specimen, used to judge occupational exposure against a population with acceptable exposure. It complements airborne exposure limits.

An occupational exposure guideline for airborne concentrations of a substance, generally expressed as a time-weighted average over a workday. It applies to healthy adult workers, not the general public.

The study of how absorption, distribution, metabolism, and excretion change with dose, especially at high or repeated exposures. It explains why kinetics observed at low doses may not predict overdose behavior.

The relationship between the concentration of a toxicant at its target site and the resulting biological effect over time. It covers receptor interactions, signal disruption, and recovery of function.

Highly reactive oxygen-containing molecules such as superoxide and hydroxyl radicals that damage lipids, proteins, and DNA. Excess production overwhelms antioxidant defenses and causes oxidative stress.

A cysteine-containing tripeptide that conjugates electrophiles and detoxifies peroxides. Depletion of hepatic stores permits reactive metabolites to bind cellular macromolecules and cause necrosis.

Agonists bind receptors and activate signaling, whereas antagonists occupy the site without activation and block agonist effects. Many poisons act by mimicking or blocking endogenous ligands.

The ratio between a dose producing toxicity and a dose producing the desired effect. A narrow index means small dosing errors or interactions can cause serious poisoning.

A recognizable pattern of signs and symptoms suggesting a particular class of poisoning, such as cholinergic, anticholinergic, opioid, or sympathomimetic. It guides early empiric treatment before laboratory confirmation.

The difference between measured serum cations and anions, calculated as sodium minus chloride and bicarbonate. An elevated gap with metabolic acidosis narrows the differential toward certain ingestions and metabolic disorders.

The difference between measured and calculated serum osmolality. It reflects the presence of unmeasured osmotically active substances such as ethanol, methanol, or ethylene glycol.

Interventions intended to reduce gastrointestinal absorption of an ingested poison, including activated charcoal, gastric lavage, and whole-bowel irrigation. Benefit is time-dependent and must be weighed against aspiration and injury risk.

A highly adsorptive carbon preparation given orally to bind poison remaining in the gut. It is most effective within the first hour and is contraindicated when airway protection is inadequate.

Administration of a polyethylene glycol electrolyte solution to flush unabsorbed material through the gastrointestinal tract. It is used for sustained-release products, packets, and metals not bound by charcoal.

Removal of a poison from blood outside the body by hemodialysis, hemoperfusion, or related techniques. It is most useful for substances with low volume of distribution, low protein binding, and long half-lives.

A substance that counteracts a poison through a specific mechanism, such as receptor blockade, chelation, or metabolite replenishment. Antidotes supplement but do not replace supportive care.

A molecule that binds metal ions to form a stable complex that can be excreted. Examples include dimercaprol, edetate calcium disodium, and deferoxamine for specific metal poisonings.

A predictable cluster of signs and symptoms following reduction or cessation of a substance on which the body has become physically dependent. Severity and timing depend on the drug and its half-life.

Reduced response to a given dose after repeated exposure, requiring larger amounts for the same effect. It may be pharmacokinetic, through increased metabolism, or pharmacodynamic, through receptor adaptation.

Severe alcohol withdrawal with confusion, tremor, autonomic hyperactivity, and hallucinations, typically appearing days after the last drink. It is potentially fatal and requires benzodiazepines and supportive care.

A potentially life-threatening toxidrome of altered mental status, autonomic instability, and neuromuscular hyperactivity, such as clonus and hyperreflexia. It results from serotonergic excess, often after drug combinations.