OMSB Pharmacist Exam key terms

The fraction of an administered dose of unchanged drug that reaches systemic circulation. Intravenous administration is defined as 100%; oral bioavailability is reduced by incomplete absorption and first-pass metabolism. It is a core parameter for comparing formulations and routes.

Presystemic elimination of an orally absorbed drug by gut wall and liver enzymes before it reaches systemic circulation. It lowers oral bioavailability and explains why some drugs require much larger oral than intravenous doses.

An apparent volume relating the amount of drug in the body to its plasma concentration. A large value suggests extensive tissue distribution; a small value suggests confinement to plasma. It determines the loading dose needed to achieve a target concentration.

The volume of plasma from which a drug is completely removed per unit time. Total clearance is the sum of renal, hepatic and other clearances, and together with volume of distribution it determines half-life and maintenance dose rate.

The time required for plasma concentration of a drug to fall by half during elimination. It governs how quickly steady state is reached (about four to five half-lives) and how long a drug persists after stopping therapy.

The condition in which drug input equals elimination, so plasma concentration remains stable over each dosing interval. It is typically reached after four to five half-lives of regular dosing and is the appropriate time for therapeutic drug monitoring.

An initial larger dose given to reach a target plasma concentration rapidly rather than waiting several half-lives. It is calculated from volume of distribution and target concentration, and is independent of clearance.

An inactive or less active chemical derivative that is converted in the body, usually by enzymatic or chemical hydrolysis, into the active drug. Prodrugs are designed to improve absorption, stability, taste or tissue targeting.

The systematic relationship between a molecule's chemical structure and its biological activity. Medicinal chemists modify functional groups to optimise potency, selectivity, solubility and metabolic stability while reducing toxicity.

The spatial arrangement of chemical features in a molecule that is essential for a specific biological activity. It is used to design new analogues and to explain why structurally different drugs can act at the same receptor.

A ligand that binds a receptor and activates it to produce a biological response. Full agonists produce maximal response; partial agonists produce a submaximal response even when all receptors are occupied.

A drug that binds and activates a receptor but produces less than the maximal possible response, even at full receptor occupancy. Partial agonists can act as functional antagonists when competing with a full agonist.

A drug that binds a receptor without activating it and blocks the effect of agonists. Competitive antagonists can be overcome by higher agonist concentrations; non-competitive antagonists reduce the maximal response.

A ratio expressing the margin of safety of a drug, commonly the toxic dose divided by the effective dose. A narrow index means small dose changes can cause toxicity, so monitoring and careful titration are required.

Measurement of drug concentrations in blood to individualise dosing, used for drugs with narrow therapeutic indices, unpredictable pharmacokinetics or concentration-dependent toxicity. Interpretation requires knowing the sampling time relative to dosing.

Increased synthesis or activity of drug-metabolising enzymes after repeated exposure to an inducer, which lowers concentrations of co-administered substrates. Effects develop over days to weeks and resolve slowly after the inducer is stopped.

Reduction of drug-metabolising enzyme activity by an inhibitor, raising concentrations of co-administered substrates and increasing toxicity risk. Inhibition is often rapid and competitive, in contrast with the slower process of induction.

A change in a drug's effect caused by another drug, food, herb or disease state. Interactions may be pharmacokinetic, altering absorption, distribution, metabolism or excretion, or pharmacodynamic, altering effects at the site of action.

A harmful or unintended response to a medicine used at normal doses. Reactions are classified by mechanism, for example dose-related, idiosyncratic or allergic, and must be documented and reported through pharmacovigilance systems.

The science of detecting, assessing, understanding and preventing adverse effects or any other drug-related problem. Activities include spontaneous reporting, signal detection, periodic safety reports and risk minimisation measures.

A medicine for which small changes in dose or blood concentration produce clinically important changes in efficacy or toxicity. Examples include digoxin, lithium and warfarin, which commonly require concentration monitoring and careful dose adjustment.

The absence of a significant difference in the rate and extent of absorption between two pharmaceutical products containing the same active ingredient. It is demonstrated by comparative bioavailability studies and supports interchangeability of generic products.

An inactive ingredient included in a dosage form to aid manufacture, stability, absorption or patient acceptability. Excipients can cause harm in some patients, for example lactose in lactose intolerance or benzyl alcohol in neonates.

The quality-assurance system ensuring medicinal products are consistently produced and controlled to quality standards. It covers premises, equipment, personnel, documentation, validation and quality control testing of each batch.

An official compendium of recognised quality standards for medicines, including tests, assays and specifications. It provides the legal reference for identity, purity and strength of medicinal substances in a jurisdiction.

A continually updated list of medicines approved for use in a health institution or health system, with guidance on prescribing and restrictions. Formulary management balances efficacy, safety and cost to promote rational medicine use.

A lawful written or electronic order from an authorised prescriber for a medicine to be dispensed to a named patient. Required elements typically include patient details, drug, dose, directions, quantity and prescriber signature.

A preventable mistake occurring during the dispensing process, such as wrong drug, strength, dose or label instructions. Reporting and root-cause analysis are used to improve systems rather than to blame individuals.

Any preventable event that may cause or lead to inappropriate medication use or patient harm. Errors can occur at prescribing, transcribing, dispensing, administration or monitoring stages and are addressed through system safeguards.

Structured communication in which the pharmacist provides information and advice so the patient can use medicines safely and effectively. It addresses purpose, dose, timing, adverse effects, storage and what to do about missed doses.

The extent to which a patient's behaviour matches agreed recommendations from a prescriber, including timing, dose and duration. Pharmacists improve adherence through education, simplification of regimens and addressing barriers such as cost.

A formal process of obtaining and comparing a patient's complete medication history across transitions of care. It identifies discrepancies, prevents omissions and duplications, and reduces harm from unintended changes.

Prescribing and using medicines appropriately to the patient's clinical need, in doses meeting individual requirements, for an adequate period and at the lowest cost. It requires accurate diagnosis, correct drug selection and adherence support.

A medicine subject to special legal controls because of abuse or dependence potential. Requirements typically include secure storage, record keeping, restricted prescribing authority and witnessed destruction of unused stock.

A patient's voluntary agreement to a treatment or procedure after receiving adequate information about benefits, risks and alternatives. Pharmacists obtain consent for services such as vaccination and for sharing confidential health information.