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| Question | Answer |
| Pharmacokinetics | The process by which a drug is absorbed, distributed, metabolised and eliminated by the body |
| Pharmacodynamics | The interactions of a drug and the receptors responsible for its action in the body |
| The Life Cycle of a Drug | Consists of 4 stages: Absorption, distribution, degradation and excretion |
| Water-soluble substance | An ionised (charged) particle that crosses through pores in capillaries, but not in cell membranes |
| Lipid-soluble substance | A non-ionised substance that can cross pores, cell membranes and the blood-brain-barrier |
| Dissociation constant (pKa) | Indicates the pH where 50% of the drug is ionised and 50% is non-ionised, and affects a drugs solubility, permeability, binding and other characteristics |
| Bioavailability | The fraction of the administered dose of a drug that reaches the bloodstream |
| Depot Site/Silent Receptor | When drugs bind to cells that are not receptors e.g. fat, muscle, organs, bones etc. |
| Plasma half-life | The time it takes for plasma concentration of a drug to drop to 50% of initial level |
| Whole body half-life | The time it takes to eliminate half of the body content of a drug |
| 1st Order Kinetics | A constant fraction of drug is eliminated per unit of time |
| Zero Order Kinetics | Rate of elimination is constant and independent of drug concentration |
| Therapeutic Index | The ratio between the dosage of a drug that causes a lethal effect and the dosage of a drug that causes a therapeutic effect - This measures the relative safety of a drug - TI = LD50/ED50 |
| Effective Dose (ED50) | Dose at which 50% of the population shows a response |
| Lethal Dose | Dose at which 50% of the population dies |
| Potency | The amount of a dose of a drug required to produce an effect of given intensity |
| Efficacy | The maximum response achievable from an administered dose |
| Tolerance (Desensitization) | The loss of responsiveness to a given dose with repeated constant exposure |
| Sensitization | An increase in responsiveness to a given dose with repeated exposure |
| Cumulative Effects | When repeated administration of a drug produces effects that are more pronounced than those produced by the first dose |
| Additive Effects | When the effect of two chemicals is equal to the sum of the effect of the two chemicals taken separately |
| Synergistic Effects | When the effect of two chemicals taken together is greater than the sum of their effects taken separately |
| Antagonistic Effects | When the effects of two chemicals taken together is less than the sum of their effects taken separately |
| Agonists | Facilitate receptor responses |
| Antagonists | Inhibit receptor responses |
| Up-regulation | An increase in sensitivity at the cellular level due to an increase in the number of receptors due to an increase in stimulation |
| Down-regulation | A decrease in sensitivity at the cellular level due to an decrease in the number of receptors due to an decrease in stimulation |
| Law of Mass Action | When a drug combines with a receptor, it does so at a rate which is dependent on the concentration of the drug and of the receptor |
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