Pharmacodynamics Quiz 2020_Graded A | Pharm 5001 Pharmacodynamics Quiz_100% Correct

Pharmacodynamics Quiz 2020 - 100% Correct 1. The set of properties that characterize the effects of a drug on the body is called (A) Distribution (B) Permeation (C) Pharmacodynamics (D) Pharmacokinetics (E) Protonation Answer: C. Pharmacodynamics is the term given to drug actions on the body. Drug-Receptor Interaction 2. What does the term tachyphylaxis mean? (A) An increase in the rate of the response, for example, an increase of the rate of muscle concentration (B) Immediate hypersensitivity reactions (ie, anaphylaxis) (C) Prompt conformational changes of the receptor such that agonists, but not antagonists, are able to bind and cause a response (D) Quick and progressive rises in the intensity of drug response, with repeated administration, even when the doses are unchanged (E) Rapid development of tolerance to the drug’s effects Answer: E. Tachyphylaxis is loosely defined as rapidly developing tolerance to the effects of a drug that is administered repeatedly, even if the dosages given after the first one are not changed or even progressively increased to overcome the phenomenon. It is sometimes also called desensitization or down-regulation of the receptor(s), but those phenomena do not explain all the mechanisms by which tachyphylaxis (or tolerance in general) occurs. The mechanism behind the development of tachyphylaxis or slower-developing drug tolerance in general-varies depending on which drug is being used, the biochemical processes by which the drug exerts its effects, and what the effector and the response(s) are. For example, consider the rapidly diminished response of a variety of cells/tissues to repeated administration of amphetamine, which acts by releasing neuronal norepinephrine. Challenge the system repeatedly and the amount of intraneuronal NE available to be released-which is essential for causing the ultimate response-goes down. Another example, with more clinical relevance, is the somewhat slower development of “tolerance” of airway smooth muscles, and their ability to relax (i.e., cause bronchodilation) in response to repeated administration of β-adrenergic agonists, such as albuterol, arguably the most widely used adrenergic bronchodilator for asthma. (Note: There is no magical number that distinguishes between tachyphylaxis and “regular” tolerance. The brevity with which the tolerance develops is the key point in the working definition of tachyphylaxis.)3. A patient is taking L-dopa as a treatment for their Parkinson’s Disease. Over a 3 month period of taking the drug they notice that the effect of the same dose of L-dopa is diminished. Assuming that the disease has not progressed in this 3 month period, and without knowledge of the physiological mechanism, it can be stated that the decrease in effectiveness of the L-dopa is due to: (A)Receptor inactivation (B) Tolerance (C) Receptor desensitization (D)Receptor down-regulation (E) An increase in the refractory period Answer: B. Tolerance may be defined as when repeated administration of a drug leads to an increased dose being required to produce the same effect. This is the same as saying the same dose gives a diminished response after time. This is a general term that does explain the decrease in L-dopa effectiveness. Receptor inactivation is when repeated drug-receptor binding leads to the receptor being turned off. This could be described as complete desensitization. Receptor desensitization is a process which is defined by a decreased ability of receptors to respond to stimulation by a drug. That is the drug binds to the receptor but does not produce its usual response within the cell. Down-regulation is a process which is defined by repeated drug-receptor interaction resulting in the removal of the receptor from the site of drug-receptor interaction. Although these may explain to some extent the decrease in effect of L-dopa without know the mechanism you cannot specify this as the reason there has been a decrease in the L-dopa effectiveness (there are other mechanisms that may also explain this change). An increase in refractory period would affect a response that involves the activation of voltage-dependent channels. This would decrease the frequency of response to stimulation and so decrease the response. Levodopa acts by increasing dopamine levels in the brain increasing action at the receptor. Most dopamine receptors are involved with G protein activation though binding to some receptors will decrease voltage-dependent Ca2+ channel activity. This will hyperpolarize the membrane and so an increase in refractory period would if anything increases the patient response to L-dopa (lots of assumptions made here). There is no evidence given that Ldopa produces this effect and so you can not specify this as the reason there has been a decrease in the L-dopa effectiveness. 4. A patient has been taking a dopamine agonist for several months in order to treat their Parkinson’s Disease. The drug has been starting to lose it’s effectiveness due to receptor sequestration decreasing the number of receptors on the target cell membrane. This process of receptor sequestration is known as: (A)Tachyphylaxis (B) Desensitization (C) Down-regulation (D)Tolerance (E) Inactivation Answer: C. Down-regulation is a process which is defined by repeated drug-receptor interaction resulting in the removal of the receptor from the site of drug-receptor interaction. This would include receptor sequestration. Therefore the process described that leads to thedecreased response of a patient to a drug over time is down-regulation. Tachyphylaxis is defined as a diminished response to a drug over time. Tachyphylaxis definitely describes an acute diminished response to a drug BUT some will argue that a diminished response observed over several months is better described by the term tolerance. Whichever side you are on tachyphylaxis is a general term whereas the question is specifically asking what describes the actual process of receptor sequestration. Desensitization is a process which is defined by a decreased ability of receptors to respond to stimulation by a drug. That is the drug binds to the receptor but does not produce its usual response within the cell. Although this could explain a decreased response of a patient to a drug over time it does not involve receptor sequestration. Tolerance may be defined as when repeated administration of a drug leads to an increased dose being required to produce the same effect. There is some argument over the use of tachyphylaxis and tolerance, however the example of a decreased response to a dopamine agonist over time definitely is tolerance. The question however is specifically asking what describes the actual process of receptor sequestration. Inactivation is when repeated drug-receptor binding leads to the receptor being turned off. This could be described as complete desensitization. This does not describe a mechanism that involves receptor sequestration. 5. Carbamazepine, a drug used in the treatment of epilepsy is metabolized by the one of the cytochrome P450 enzymes. However, it also induces this enzyme such that over time, the therapeutic effectiveness of carbamazepine is reduced. Which of the following best describes this phenomenon? (A)Pharmacodynamic tolerance (B) Tachyphylaxis (C) Up regulation (D)Pharmacokinetic tolerance (E) Sensitization Answer: D. This is an example of a pharmacokinetic tolerance where one drug affects the metabolism of another drug. Pharmacodynamic tolerance would be a drug that interacts with another drug at the receptor level. Tachyphylaxis and up-regulation and sensitization are changes that occur at the receptor themselves. 6. The effects of atropine at the muscarinic receptor can be overcome by increasing the level of acetylcholine. What type of bond is atropine LEAST likely to make with the muscarinic receptor? (A)Ionic bond (B) Van der Waal’s bond (C) Hydrogen bond (D)Covalent bond Answer: D. Atropine is a competitive antagonist at the muscarinic receptor. It is unlikely therefore that it will make a covalent bond with the receptor since this type of bonding is very strong.