Pharmacodynamics NURS 1060 Exam 2 PDF

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wgaarder2005

Uploaded by wgaarder2005

Lakeland Community College

NURS

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pharmacodynamics drug responses receptors medicine

Summary

This document is a presentation on pharmacodynamics for a nursing exam. It covers key concepts such as dose-response relationships, drug interaction with receptors, efficacy, and the therapeutic index. These concepts are important for understanding how drugs affect the body.

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Pharmacodynamics NURS 1060: Exam 2 OUTCOME  Discusscritical thinking and clinical reasoning to provide quality patient care. COMPETENCY  Discuss critical thinking and clinical judgment used to provide accurate and safe medication administration CONCEPT  ClinicalDecision...

Pharmacodynamics NURS 1060: Exam 2 OUTCOME  Discusscritical thinking and clinical reasoning to provide quality patient care. COMPETENCY  Discuss critical thinking and clinical judgment used to provide accurate and safe medication administration CONCEPT  ClinicalDecision Making: A process used to examine and determine the best actions to meet desired goals; requires anticipating, recognizing and organizing patient problems to respond with urgency and/or importance in a preferential order to avoid or minimize adverse changes in a patient’s condition. Unit Outcomes  Define pharmacodynamics  Define efficacy  Discuss drug dose response relationship  Define agonist and antagonist  Discuss the concept of affinity of a drug and receptor  Discuss therapeutic index as it relates to toxicity Pharmacodynam = The study of what drugs do to the body and ics how they do it  To accomplish the therapeutic objective, nurses must have a basic understanding of pharmacodynamics  Educatingpatients about their medications  Making PRN decisions  Morphine or acetaminophen?  Evaluating patients for drug responses  Benefit or Harm?  Collaborating with prescriber about drug therapy Maximum Benefit, Minimum Harm Concepts Related to Pharmacodynamics  Dose-response relationships  Drug-receptor interactions  Drug responses that do not involve receptors  Interpatient variability in drug responses  The therapeutic index Relationship between the size of an administered dose and the intensity of the response Dose- produced Response Relationshi ps Determines How much we need The minimum The maximum to increase the amount of drug we response a drug can dosage to produce can use elicit the desired increase in response Dosage increases, Dose- response increases Response Relationshi Dosage is adjusted ps to achieve desired response Maximum response a drug can produce Maximal Match the intensity of the response with the patient’s Efficacy need. Very high maximal efficacy is not always more desirable. Maximal Efficacy  Dose-response curves demonstrating efficacy.  Efficacy is an index of the maximal response a drug can produce. The efficacy of a drug is indicated by the height of its dose-response curve.  Usethe concept of efficacy to determine which drug to Apply this administer for a mild headache? Concept  Meperidine (Demerol)  Pentazocine (Talwin)  Acetaminophen (Tylenol) Answer  acetaminophen  The goal is to match the intensity of the response to the patient’s needs; therefore, a drug with high maximal efficacy is not always most desirable. Meperidine and pentazocine have a higher maximal efficacy than acetaminophen; therefore, acetaminophen is the most desirable drug for a headache rated as “mild.” Drug-Receptor Interactions Drugs Receptors = Chemicals that = Special produce effects chemicals in by interacting the body that with other most drugs chemicals interact with to produce effects  A receptor is a macromolecule (protein or enzyme) of a cell to which a drug binds to produce its effects.  The body’s Receptor molecules that interact with receptors include: hormones, neurotransmitters, and other regulatory molecules When a drug binds to a receptor, it can:  mimic the action of the endogenous regulatory molecules  increase or decrease the rate of physiologic activity normally controlled by that receptor  blockthe action of the endogenous regulatory molecules Cell Membrane–Embedded Enzymes: located on cell surface Ligand-gated ion channels: regulate the Four flow of ions (Na, K, Ca) Primary G protein–Coupled Receptor systems Receptor G Protein is the binding protein on the receptor Effectors are enzymes Families Receptor on the cell membrane to the enzyme on the inside the cell Transcription factors within the cell on DNA 1. Cell membrane–embedded enzyme located on cell surface. 2. Ligand-gated ion channel Na, K, Ca. 3. G protein–coupled receptor system attach receptors on the cell membrane to the enzyme receptor inside the cell 4. Transcription factor are found within the cell on DNA Drug-Receptor Interaction Affinity  Affinity = strength of the attraction between the drug and the receptor.  Drugs with high affinity are have a strong attraction to their receptors  Drugs with low affinity have a weak attraction to their receptors. Drug-Receptor Interactions Antagonis Agonists ts Dose-Response Curve 100 80 Respons 60 40 e 20 0 0.1 1 10 100 1000 10000 Dose 100 80 60 40 20 0 0.1 1 10 100 1000 10000 = Agonist 100 80 60 40 20 0 0.1 1 10 100 1000 10000 = Agonist 100 80 60 40 20 0 0.1 1 10 100 1000 10000 = Agonist 100 80 60 40 20 0 0.1 1 10 100 1000 10000 = Agonist = Agonist = = Agonist = Drug Responses That Do Not Involve Receptors  Simplephysical or chemical interactions with other small molecules  Some examples of drugs that do not use receptors:  Antacids  Antiseptics  Saline laxatives Interpatient The dose required to produce a therapeutic Variability response can vary among patients. in Drug What variables can you identify? Responses Variables in  Age Drug  Physiological function of heart, Responses: liver, kidneys  Disease – chronic and acute  Vascular status a few  Nutrition examples Clinical Implications of Patient Variability in Drug Responses Subsequent doses may need to be The initial dose of a increased or drug is an decreased after the approximation. patient response is evaluated. Therapeutic Index  Measure of a drug’s safety  Ratio of the drug’s LD50 to its ED50  (average lethal dose to the average effective dose in 50% of the animals treated)  Thelarger/higher the therapeutic index, the safer the drug.  The smaller/lower the therapeutic index, the less safe the drug. The Therapeutic Index A, Because its LD50 is much greater than its ED50, drug X is relatively safe. B, Because its LD50 is very close to its ED50, drug “Y” is not very safe. Also note the overlap between the effective-dose curve and the lethal-dose curve. A low therapeutic index indicates that high doses may be large enough to cause harm or death. Therapeutic A high therapeutic index is more Index desirable, because the lethal dose is higher than the therapeutic dose. Therapeutic Index Example:  Patient: “Did I take my medication this morning? Well, I’m not sure. Maybe I’ll just take it now.”  Ifthis is the second dose and the medication has a low therapeutic index then?  What if it has a high therapeutic index? Answer  Ifthis is the second dose and the medication has a low therapeutic index:  Patient is more likely to experience harm  Ifthis medication has a high therapeutic index:  Patient is less likely to experience harm

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