APC Written Assessment key terms

The proportion of an administered dose of a drug that reaches the systemic circulation unchanged, together with the rate at which it arrives. An intravenous dose is taken as 100% bioavailable.

Evidence that two medicine products containing the same drug deliver it to the bloodstream at a comparable rate and extent. It is the basis for approving, and for substituting, generic products for the original brand.

Breakdown of an orally absorbed drug in the gut wall or liver before it reaches the general circulation. It lowers oral bioavailability, so an oral dose often has to be larger than the intravenous dose.

An apparent volume calculated by dividing the amount of drug in the body by its plasma concentration. A large value suggests wide distribution into tissues rather than the drug staying in blood.

The volume of plasma cleared of drug per unit time by metabolism and excretion. Clearance sets the maintenance dose rate needed to hold a target concentration once steady state is reached.

The time for the plasma concentration of a drug to fall by half once absorption is complete. It guides how often a dose is needed and predicts how long steady state will take to reach.

The point during regular dosing when the amount of drug entering the body equals the amount being eliminated, so concentrations fluctuate around a stable average. It usually takes four to five half-lives to achieve.

Elimination that proceeds at a constant amount per unit time regardless of concentration, because enzyme or transport systems are saturated. Dose increases then cause disproportionately large and unpredictable rises in plasma levels.

An initial larger dose given to reach a therapeutic concentration quickly. Its size depends mainly on the drug's volume of distribution, whereas maintenance dosing depends mainly on clearance.

An inactive or weakly active molecule that the body converts, usually by enzymes, into the active drug. The conversion step is designed to improve absorption, stability, taste or targeting of the medicine.

Any ingredient of a medicine other than the active substance, such as fillers, binders, disintegrants, coatings, preservatives and colours. Excipients aid manufacture, stability and palatability and can occasionally cause adverse reactions.

A ratio comparing the dose or concentration that causes toxicity with the one that produces the desired effect. A low index signals a narrow safety margin requiring careful dosing and monitoring.

A coating on a tablet or capsule that resists stomach acid and breaks down in the intestine. It protects acid-labile drugs or the stomach lining, so these dosage forms should not be crushed or chewed.

A drug that binds to a receptor and switches it on to produce a response. Full agonists give the maximal effect, while partial agonists produce a smaller response even when every receptor is occupied.

A drug that binds reversibly to the same receptor site as the agonist and blocks access. Raising the agonist concentration can overcome the block, shifting the dose-response curve right without lowering the maximum response.

A reduced response to a drug after repeated use, caused by adaptive changes such as receptor down-regulation or desensitisation. Higher doses are then required to achieve the same effect.

An increase in the amount or activity of drug-metabolising enzymes after repeated exposure to a triggering drug. It speeds elimination of co-administered substrate drugs and may cause treatment failure.

A large family of enzymes, found mainly in the liver and gut wall, that oxidise many medicines. Inhibition or induction of particular isoforms is a frequent cause of clinically important drug interactions.

Measuring plasma concentrations of selected drugs to individualise doses. It is used for drugs with narrow therapeutic ranges or unpredictable kinetics, such as lithium, digoxin, phenytoin and vancomycin.

A harmful, unintended response to a medicine used at normal doses. Type A reactions are dose-related and predictable from the drug's known actions, whereas Type B reactions are uncommon and idiosyncratic.

The study of how inherited genetic differences affect a person's response to medicines, including how quickly they metabolise a drug or how their receptor target behaves. It helps explain variability and guide dosing.

A combined effect of two medicines that is greater than the sum of their separate effects. It can be therapeutically useful but also raises the chance of unexpected toxicity.

The ability of bacteria, fungi or other organisms to survive exposure to an antimicrobial that would normally kill or inhibit them. It spreads by mutation and gene transfer and is driven by unnecessary antibiotic use.

The greatest response a drug can produce when all its available receptors are occupied. It differs from potency, which describes how much drug is needed to produce a given level of effect.

The Australian government program that subsidises listed prescription medicines for eligible patients, specifying which medicines, strengths, indications and prescriber types can attract a subsidy.

In Australia, a pharmacist-only medicine sold without a prescription after the pharmacist assesses the patient. It is kept behind the counter and its supply may need to be recorded.

In Australia, a prescription-only medicine that can be supplied only on a valid prescription from an authorised prescriber, apart from narrowly defined emergency or continuing-supply situations.

In Australia, a controlled drug of dependence such as morphine or oxycodone. It carries strict requirements for prescribing authority, secure storage, record keeping and reporting because of high misuse potential.

A Pharmaceutical Benefits Scheme prescription that is subsidised only once approval or a streamlined authority code is obtained, because the medicine is restricted to particular indications, quantities or prescriber types.

Dispensing a different brand of the same drug, strength and dosage form from the one prescribed. Under the Pharmaceutical Benefits Scheme it is allowed unless the prescriber indicates otherwise, and the brand supplied is recorded.

A product containing the same active ingredient, strength and dosage form as an originator brand, approved after showing bioequivalence once patent and data protection expire. It is usually less expensive.

Preparing a medicine for an individual patient when no suitable commercial product exists or is available, following documented formulas, using quality ingredients and keeping records of the preparation.

A formal process of collecting the most accurate list of all medicines a person is taking, checking it against reliable sources and resolving discrepancies, especially at admission, transfer and discharge.

A container, such as a sealed blister pack, that sorts a person's medicines into time slots across a week. Pharmacists pack them to support adherence and reduce administration errors.

Australia's policy approach to medicine use: choosing management options wisely, selecting suitable medicines when needed, and using them safely and effectively by health professionals and consumers together.

A standardised leaflet written in plain language for people taking a prescription medicine. It covers what the medicine is for, how to use it, side effects, warnings and storage.

The ongoing detection, assessment, understanding and prevention of adverse effects and other problems with medicines. In Australia it relies on reports to the Therapeutic Goods Administration, including reports from pharmacists.

Prescribing or supplying a registered medicine outside the indications, dose, route or patient group described in the approved product information. It can be appropriate when evidence supports it and should be documented.