Reference

Glossary

Terms the examiners expect defined precisely. Where two terms are routinely confused they are placed next to each other on purpose.

Kinetics

Bioavailability (F): The fraction of an administered dose reaching the systemic circulation unchanged. Intravenous administration is 1 by definition.
Bioequivalence: Two products whose rate and extent of absorption differ by no more than the accepted margin — not the same claim as equal bioavailability.
Biosimilar: A biological product highly similar to an approved reference biologic, with no clinically meaningful differences. Never called generic.
Volume of distribution (V_d): The theoretical volume needed to contain the total drug in the body at the plasma concentration. A large V_d means extensive tissue distribution, not a large person.
Clearance (CL): Volume of plasma cleared of drug per unit time. Additive across organs.
Half-life (t½): Time for plasma concentration to halve. Steady state is reached after roughly five half-lives, as is complete elimination after stopping.
First-order elimination: Rate proportional to concentration; a constant fraction is removed per unit time. Most drugs, most of the time.
Zero-order elimination: Rate constant and independent of concentration because the enzyme is saturated. Phenytoin, ethanol, high-dose aspirin.
First-pass metabolism: Metabolism between absorption and the systemic circulation, chiefly hepatic. The reason some oral doses are far larger than intravenous ones.

Affinity: How strongly a drug binds its receptor. Antagonists have affinity but no efficacy.
Efficacy: The maximum effect a drug can produce once bound. Distinguishes a full from a partial agonist.
Potency: The concentration required to produce a given effect — a statement about position on the dose axis, not about maximum effect.
EC₅₀: Concentration producing half the maximal response.
Therapeutic index: Ratio of toxic to effective dose. Narrow-index drugs are the ones requiring monitoring: digoxin, lithium, phenytoin, warfarin, gentamicin.
Competitive antagonism: Reversible, at the same site; shifts the agonist curve rightward with no change in maximum. Surmountable by more agonist.
Non-competitive antagonism: Reduces the maximum response and cannot be overcome by more agonist.
Tachyphylaxis: Rapid loss of response on repeated dosing, over minutes to hours.

Excipient: Any component other than the active ingredient: diluent, binder, disintegrant, lubricant, glidant.
Disintegration and dissolution: Disintegration is the tablet breaking up; dissolution is the drug entering solution. Dissolution is usually the rate-limiting step.
BCS class: Biopharmaceutics Classification System, by solubility and permeability. Class II (low solubility, high permeability) is where formulation earns its keep.
Tonicity: Effective osmotic pressure relative to plasma. Parenteral products should be isotonic, near 290 mOsm/kg.
Eutectic mixture: Two solids that liquefy on mixing because the mixture's melting point is below room temperature. Classically menthol and phenol.

Short	Full
ADME	Absorption, distribution, metabolism, excretion
AUC	Area under the concentration–time curve
BNF	British National Formulary
CD	Controlled drug
DOAC	Direct oral anticoagulant
GSL	General sale list
INR	International normalised ratio
MHRA	Medicines and Healthcare products Regulatory Agency
OSPE	Objective structured pharmaceutical examination
POM	Prescription-only medicine
SPC	Summary of product characteristics
TDM	Therapeutic drug monitoring