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Pharmacology 2060A/B
Angela Nissen

Module 7 Pharmacodynamics – Dose Response Relationships 7.1 Intro • pharmacodynamics: study of what drug does to the body o study biochemical and physiological effects of drugs and mechanisms by which drugs produce  effects o to provide optimal pharmacotherapy, combine pharmacokinetics and pharmacodynamics 7.2 Dose Response Curves • increasing dose of drug results in increased plasma concentrations • increasing dose also increases response to drug • • dose response curves are monotonic – response increases as dose increases o not linearly though, semi logarithmic • Phases of Dose Response Curve o Phase 1 – doses are too low to elicit a clinically relevant response o Phase 2 – response is graded and nearly linear o Phase 3 – larger doses do not lead to greater response, larger doses may cause toxicity • Efficacy o Measure of how effective a drug is at a given dose o Maximal efficacy – represents the maximal effect that a drug is capable of achieving o Maximal efficacy is read off the dose response curve by looking at maximum height • Do we always choose the drug with the highest efficacy to treat patients? o No o Choose drug and dose that are therapeutically effective with fewest side effects o Health care professionals often titrate the dose of the drug  Start with low dose of drug and slowly increase the dose while monitoring the patients response • Potency o The amount of drug required to elicit a pharmacological response o High potency does not mean more therapeutically effective o In order to compare potency, the drugs must produce the same therapeutic effect  Ex. Cant compare potency of medication for pain relief and medication that measures blood pressure o Amore potent drug will require smaller dosage to achieve desired effect than a less potent drug o Potency is determined by comparing the dose required to produce the half maximal response  Called the ED50 o Drugs with lower ED50 are said to be more potent than a drug with a high ED50 7.3 Drug Receptors • how do drugs produce effects? o Most drugs act on cellular macromolecules (receptors, enzymes, etc)  Majority are targeted to enzymes, but some act on receptors, ion channels, etc. o Typical drug action involves binding of drug to macromolecule target  The complex is then able to produce a biological effect o Drugs typically mimic an endogenous compound in the body  Ex. Norepinephrine binds to receptors on heart and increases heart rate • Drugs that mimic NE bind same type of receptor • Do all drugs act on cellular targets? o NO o Most drugs act on cellular targets o Best example – antacids  Drugs that neutralize stomach acid to provide symptomatic relief of GI disorders  Simply bases that neutralize stomach acids – don’t bind any cellular target • Types of Drug Receptors o Receptor: protein that drug binds and produces a measurable response  Majority are proteins that are able to translate extracellular signals into biological responses o Most important types:  Ligand gated ion channels  GPCRs  Enzyme linked receptors  Int
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