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Dose-Response Relationship - Pharmacodynamics Lecture | Potency, Efficacy, Therapeutic Index etc

📝 All videos on General Pharmacology: https://www.nonstopneuron.com/post/ge... 🌐 Explore our entire animation video library: https://www.nonstopneuron.com/ ● Follow me at: • Instagram:   / nonstopneuron   • Facebook:   / nonstopneuron   Dose-Response Relationship Pharmacodynamics lecture: In dose-response relationship, we study how much of an effect is produced by a drug. Strictly speaking, it's a study of the plasma-concentration, response relationship. As we increase the dose, the response also increases. The highest response that can be achieved with a drug is called maximal response or ceiling response. The shape of a simple dose-response curve is a hyperbola. This is because the receptors respond to fractional changes in the dose, rather than absolute change. Because of this, during the experiment, the dose is increased by multiplication rather than addition. But if we plot the multiplying numbers on a linear scale, most of the doses get crammed up in the small initial part of the graph. This makes evaluation very difficult in this part. To solve this problem, we use a logarithmic scale on the x-axis. On this scale, the shape we get is sigmoid. In this log dose-response curve, the middle part is almost straight. This makes the evaluation of response at different doses, as well as, the comparison between drugs easy. Also, we can accommodate large doses in a small graph. ED50 is the dose that produces half of the maximal response. Potency refers to the amount of drug required to produce a certain response. It is indicated by the position of the curve on the x-axis. It helps choose the dose of the drug. Efficacy refers to the highest response that can be achieved with a drug. It is indicated by the height of the curve on the Y-axis. It helps make the choice of drug. Potency and efficacy are independent of each other. And in clinical practice, efficacy is more important. Because when treating a patient, it is more important that the desired therapeutic effect is achieved. It does not matter if we need to increase the dose for that, as long as the dose is safe. A steeper curve means a small change in dose produces a large variation in response. With such a drug, the dose needs to be calculated more carefully. But if the curve is flatter, a standard dose can be given to most of the patients. This was all about the graded responses. But if the responses are all-or-none type, we cannot plot them in the same way on the Y axis. So to study them, increasing doses of a drug are given to a group of subjects, and the percentage of subjects showing a specified response is plotted. This produces a similar sigmoid curve. Here the ED50 means a dose that produces a specified response in 50% of the study population. The median toxic dose is the dose that produces toxic effects in 50% of the study population. And median "lethal" dose is the dose that kills 50% of the recipients. Therapeutic index is equal to LD50 divided by ED50. It shows how safe is the drug. To be clinically useful, it needs to be at least more than one. However, in clinical practice, a more relevant parameter (than the therapeutic index) is the therapeutic range. It is a range between minimum effective dose to maximum tolerated dose. Specificity refers to how many types of effects a drug can produce in the body. Selectivity refers to whether a drug can produce one effect more preferentially over other effects. If DRCs for different effects are wide apart, the drug is called selective. Therapeutic efficacy refers to the degree of relief or cure rate achieved with a drug. Thus it is a broader term than simply efficacy. Chapters: 00:00 Introduction 00:47 Parts of Dose-Response Relationship 02:18 Obtaining Dose Response Curve 04:41 Law of Mass Action 07:40 Limitation of Simple Dose-Response Curve 08:33 Log Dose Response Curve 10:23 Effective Dose 50 (ED50) 11:17 Potency 13:20 Efficacy 16:27 Slope 17:46 Graded vs Quantal Response 19:00 Quantal Dose Response Curve 20:41 Median Effective Dose (ED50) 21:47 Median Toxic Dose (TD50) 22:21 Median Lethal Dose (LD50) 22:38 Therapeutic Index 23:44 Therapuetic Range 25:26 Specificity 26:54 Selectivity 28:06 Therapeutic Efficacy 29:20 Risk Benefit Ratio 30:31 Summary 35:36 Bonus Points Dr Vipul Navadiya Nonstop Neuron Medical Animation Medical Animation Videos DISCLAIMER: This video is for education purposes only. Although every effort is made to ensure the accuracy of the material, viewers should refer to the appropriate regulatory body/authorized websites, guidelines, and other suitable sources of information as deemed relevant and applicable. In view of the possibility of human error or changes in medical science, any person or organization involved in the preparation of this work accepts no responsibility for any errors or omissions, or results obtained from the use of information in this video.