Pharmacology Notes Pharmacology – drug action, how medicines work, how body processes them • Pharmacodynamics à effects of drug on body • Pharmacokinetics and drug metabolism à effects of body on drug Glossary of Terms Terms Definition/Description Agonist Ligand/small molecule that binds to receptor (usually orthosteric binding site) and activates receptor e.g. acetylcholine Antagonist Binds to orthosteric site of receptor, but has intrinsic activity of 0 so does not activate it e.g. atropine Ligand A molecule that binds to another (usually larger) molecule Dose-response or concentration effect relationship Dose-response – refers to adding drug to a living system like a body Concentration-effect e.g. guinea-pig ileum Orthosteric binding Binding to the active site Allosteric binding Site that differs from the orthosteric binding site Competitive binding Will compete for the binding site Non-competitive binding Binding to a different site from the orthosteric site – doesn’t necessarily mean it has to bind a receptor – could bind downstream e.g. interact with G proteins or ion channel Efficacy Ability to initiate a maximum response after receptor binding Potency Measured by measuring functional physiological response and finding EC50, the lower the value, the more potent the drug EC 50 Effective concentration to cause a half maximal response pD 2 -logEC50 K D Dissociation constant - concentration of ligand that results in half occupancy of receptors form a ligand-receptor complex (applies a 1:1 ligand: receptor ratio) Indicator of affinity, measured by a radioactive ligand (K B for antagonist) Affinity Strength of binding of drug to its target, preferability with high specificity K B Dissociation constant of antagonist Found from schild plot or direct binding experiment Desensitization v. tachyphylaxis Desensitisation – biological response to drug diminishes when it is given continuously or repeatedly, down regulation of receptor – done through kinases à arrestin binding etc. Tachyphylaxis – acute rapid decrease in response to drug after its administration, like tolerance Terms mean the same thing Selectivity Ability of drug to bind preferentially to one site over another. As no drugs are entirely specific, you get that one drug is more selective to a receptor over another à has preference to one site over another, e.g. muscarine is more selective for muscarinic over nicotinic, beta blockers are antagonists that bind to B receptors, non-selective would be something that binds to either B1 or B2, or something else may be selective over B1 than B2 Specificity Ability of a given drug concentration to produce one effect over another. Chemical binding interaction between the ligand and the
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Pharmacology Notes - StudentVIP · Pharmacology Notes Pharmacology – drug action, how medicines work, how body processes them • Pharmacodynamics à effects of drug on body •
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o Receptors–agonists,antagonists,modulatorso Ionchannels–blockers,modulatorso Enzymes–inhibitors,falsesubstrateso Transporters–blockers,falsesubstrates
o Endogenousandreleasedmainlyfromnerveso Activatesanorthostericbindingsiteonseveralreceptors
§ Muscarinic§ Nicotinic
o ChangesphysiologicalstateofcellthathasreceptorsthatbindtoAch
• Bindingforcesbetweenagonistandreceptor
o Electrostatic(charge)–longrangebinding,initialattraction• Thenifmoleculesuitablyshapedtofitbindingsiteofreceptor
§ Hbonding§ Vanderwaals
o HydrophobicLawofmassaction–at equilibrium, rate of chemical reaction is proportional to product of concentration of reactants (drug and free receptor)
o Maxresponsecanoccurwithoutfullreceptoroccupancyo Transductionpathwayscanamplifytheeffecto KDisforagonistsandantagonistsbecauseitreflectsaffinityoftheligandandnotintrinsic