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The Mechanisms of Drug Action course aims to provide an understanding of the basic mechanisms of drug action at the levels of both drug-receptor interactions and the effects on body systems. Attention is focused not only on the current use of drugs, but also on a framework for evaluating future therapies. Teaching Objectives
Drug action via indirect alteration of the effect of an endogenous agonist 1.5. Drug action via inhibition of transport processes 1.6. Drug action via enzyme inhibition 1.7. Drug action via direct enzymatic activity or activation of enzymes 1.8. Drug action via other miscellaneous effects 1.9. Multiplicity of effects 2. Stereoisomerism and drug ...
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Jun 30, 2024 · Abstract. Pharmacodynamics is the study of mechanisms behind drug actions. It helps us understand the behaviour of drugs inside a body and the way body reacts to the drugs. Every class of drug preserves a unique mechanism of action mostly through different receptor proteins and sometimes involving associated secondary messengers.
- dipesh.chakraborty@makautwb.ac.in
- How do drugs work? Mechanisms of Drug Action
- How do drugs bind to receptors
- Affinity vs Biological Response
- Efficacy
- Antagonists
- Reversible Competitive Antagonism
- Irreversible Antagonism
- Irreversible antagonist
- Inactivation
- Inhibitors of Acetylcholine esterase
- Reversible AChE inhibitors
- SSRI’s
- Revision
- “typical” nerve terminal
- Receptors
- G Protein coupled receptors (GPCRs) (Slow synaptic transmission)
- Enzymes
- Carrier/Transporter Molecules
- Ion Channels
Liam Anderson Dept Pharmacology & Clinical Pharmacology Describe the potential drug targets within a human body. Describe the role of receptors, enzymes, ion channels and transporters in drug action. Understand how drugs bind to receptors, and define the principles of affinity, efficacy and potency and be aware of the influence of the tissue on the...
Van der Waals forces – weak forces Hydrogen binding – stronger Ionic interactions – between atoms with opposite charges, stronger than hydrogen, weaker than covalent. Covalent binding – essentially irreversible
Concentration - response curves are not a good measure of affinity because the relationship between receptor occupancy and response is not strictly proportional : considerable amplification may exist - it may only take a low level of receptor occupancy to cause a maximal response in some tissues. Many factors downstream from the receptor binding m...
The ability of a drug to bind to a receptor and cause a change in the receptor’s action is termed “efficacy” and measured by Emax A drug with positive efficacy will activate a receptor to promote cellular response - AGONISTS A drug with negative efficacy will bind to receptors to decrease basal receptor activity - INVERSE AGONIST A drug with no eff...
A compound that binds to but does not activate (or inactivate) the receptor. Antagonists have affinity but NO efficacy. Defined by how they bind to the receptor...
Bind to the receptor in a reversible manner to compete directly with agonist binding. What effect will this have on an agonist response curve? agonist LOG [AGONIST]
Drug covalently binds to the receptor. Not reversible Reduces the number of receptors available to the agonist. What would this do to an agonist dose response curve? agonist Log [agonist]
• Sometimes at low doses an irreversibe antagonist looks like a reversible antagonist – what does this tell you about the number of receptors required to produce maximal response? agonist agonist + increasing Concentrations of irreversible antagonist [Agonist] In contrast to drugs that act on receptors which can activate or inactivate, most drugs a...
Once in the synapse neurotransmitter must be quickly removed or chemically inactivated in order to prevent constant stimulation of the post-synaptic cell There are two key mechanisms of inactivation Transport back into the pre-synaptic synapse (eg dopamine, serotonin) Enzymic degradation (eg Acetylcholine)
The effect that a specific AChE inhibitor can have on the body depends largely on the chemical properties of the molecule and the strength of the bond it forms with AChE. Irreversible AChE inhibitors are highly toxic – organophosphorus compounds or nerve gases form incredibly stable phosphorus bonds with AChE. Which resist hydrolytic cleavage for u...
Bind to AChE for a short time. Used in disorders characterized by a decrease in cholinergic function – increase the duration that Ach is available ins synapse, so one molecule can activate more receptors. Used to treat myasthenia gravis an autoimmune disorder characterized by debilitating muscle weakness. weakness is caused by a progressive breakd...
What does this stand for? Can you think of an example? What will the effect be?
On the following “stylised” synapse find at least ten sites of drug action. Describe what the likely effect of the drug is on neurotransmission For five give an example of a drug that acts in this way.
P= precursor T= transmitter D=degradation product P Mechanism of Drug Action and Drug Targets
Neurotransmitter receptors in the plasma membrane of postsynaptic cells fall into two broad classes: ligand-gated ion channels and G protein – coupled receptors. Synapses containing either type can be excitatory or inhibitory, but the two types vary greatly in the speed of their response.
Many functions of the nervous system operate with time course of seconds or minutes; regulation of the heart rate, for instance, requires that action of neurotransmitters extend over several beating cycles measured in seconds. In general, the neurotransmitter receptors utilized in slow synapses are coupled to G proteins. GPCR signalling is also co...
Many enzymes form useful drug targets eg acetylcholinesterase (neostigmine); cyclo-oxygenase (asprin), angiotensin converting enzyme (captopril). Often the drug mimics the natural substrate acting as a competitive inhibitor of the enzyme (eg captopril); in other cases the binding is non-competitive and irreversible (eg asprin). Drugs may also a...
Transportation of polar molecules across lipid membranes often requires a carrier protein. The carrier proteins embody a recognition site that makes them specific for a particular permeating species, and these sites can also be targets for drugs, whose effect is generally to block the transporter. We will consider the example of the serotonin tra...
Ion channels are protein molecules that span the cell membrane, and can switch between open and closes states, allowing the controlled entry or exit of specific ions across the cell membrane in their open state. Ion channels are highly selective for the ions that they control. The channels are all gated i.e they have particular triggers that all...
Apr 7, 2014 · Pharmacodynamics is the study of how drugs act on the body and their mechanisms of action. It involves drug-receptor interactions and explains the relation between drug effects. Pharmacodynamics provides a basis for rational drug use and design. Drugs can act through stimulation, depression, irritation, replacement or cytotoxic effects on cells.
Pharmacodynamics, the study of drug mechanisms of action, provides a comprehensive framework for unraveling the complex interactions between drugs and their molecular targets within the body. The intricate interplay between drugs and their targets dictates not only the therapeutic effects but also the potential side effects and adverse ...
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What is pharmacodynamics?
Pharmacodynamics is the study of the biochemical, cellular, and physiological actions of drugs, including the molecular mechanisms by which these actions are achieved. Most drugs are small molecules that interact with macromolecular entities, or drug targets , intrinsic to the body or to pathogens.
