Pharmacodynamics PDF

Receptors It’s a modified functional proteins, reception external signal from out side of the cell Involves drug actions on target cells and the resulting alterations in cellular biochemical reactions Most drugs chemically bind with receptors at the cellular level Drug-receptor complex...

Receptors It’s a modified functional proteins, reception external signal from out side of the cell Involves drug actions on target cells and the resulting alterations in cellular biochemical reactions Most drugs chemically bind with receptors at the cellular level Drug-receptor complex initiates physiochemical reactions that stimulate or inhibit cellular functions TYPES PHYSIOLOGICAL RECEPTORS G Protein receptor (insulin R) Ion channels (Ach R) Transmembrane enzymes (Na, K ATPase) Transmembrane, non-enzymes (Ion channels) Nuclear receptors (steroid R) Intracellular enzymes (Thyroid R) Affinity and Efficacy Ligand- any molecule which attaches selectively to particular receptors. Intrinsic activity – capacity to induce a functional change in the receptor. Affinity refers to the drug’s forces that cause a substance to bind its receptor Specificity - A drug that interacts with a single type of receptor that is expressed on only a limited number of differentiated cells will exhibit high specificity. Efficacy refers to a drug's ability to effectively activate the receptor once it has bound to it Agonists and Antagonists Agonists: mean the drug bind with receptor that stimulate its For example, salbutamol (Ventolin®) is a beta-receptor stimulant; stimulation of beta-receptors in the lungs causes bronchodilation Agonists and Antagonists Antagonist (‘blocker’); mean the drug bind with receptor that blockade it e.g. beta1-receptors in the heart will slow rate  Drug Antagonism Physical Antagonism binds to the drug and prevents its absorption like charcoal binds to alkaloids and prevents their absorption. Chemical Antagonism combines with a substance chemically like chelating agents binds with the metals. Physiological Antagonism produces an action opposite to a substance but by binding to the different receptors e.g. adrenaline is a physiological antagonist of histamine because adrenaline causes bronchodilatation by binding to β2 receptors, which is opposite to bronchoconstriction caused by histamine through H1 receptors. Pharmacological Antagonism produce no effect , shows no intrinsic activity.  Mechanism of Action of Minerals/Vitamins/Supplements Not classic Agonists/Antagonists at specific receptors Generally, they are replacing or supplementing body stores, or enhancing effects in certain diseases and disorders Generally, they are co-factors or essential elements in normal metabolic and physiological processes You will already have much more knowledge than us of specific actions and effects Variables that affect drug actions Dosage Route Drug-diet interactions. Drug-drug interations-additive effects such as seen with sedatives and ethanol. Synergism as seen with acetaminophen and codeine. Antidote—drug can be given to antagonize the toxic effects of another drug Variables that affect drug actions Age Pregnancy Body weight Gender-hormonal effects Pathologic conditions Placebo response Variables that affect drug actions Genetics-hepatic drug metabolizing enzymes===acetyltransferase. Rapid acetylators may need larger than usual dosages and conversely, smaller doses if slow acetylators Glucose-6-phosphate deficiency—develop hemolytic anemia if take antimalarials or sulfonamides Ethnicity—ACE inhibitors in African Americans Tolerance and cross tolerance