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Kaplan Pharmacology USMLE Step1 ,

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Presentation on theme: "Kaplan Pharmacology USMLE Step1 ,"— Presentation transcript:

1 Kaplan Pharmacology USMLE Step1 ,
ANS practice problems Reading assignments: Kaplan Pharmacology USMLE Step1 , Lecture notes;2009,p53-67 ; 1

2 2 types of ANS practice problems asked by NBME
1.Classic presentation :In the body of Q. you will see a graph/tracing showing effect/s of an unknown drug alone or in combination with other drugs. By looking at the response you will have to identify that unknown drug. 2.Other Qs : Effect of unknown drug/s are shown in non graphical pattern (in bars or charts or as pictogram or others).Few working examples are given in practice problem in this PP.

3 Effect of an unknown drug on Heart rate and blood pressure
Control drug effect Increased diastolic Increased TPR (Increased α1) Decreased diastolic decreased TPR (increased β2, decreased α1, directly acting vasodilators and cholinomimetics. Increased Heart rate increased β1 (May be reflex *) Decreased Heart rate Increased Cholinergic (May be a reflex) Increased pulse pressure increased β1 (increased inotropic activity)

4 Effect of α1 activators on Heart rate and blood pressure
Systemically , increase mean blood pressure via vasoconstriction. Increased BP may elicit a reflex bradycardia. Cardiac output may be decreased but also offset by increased venous return. No change in pulse pressure.

5 Effect of β activators on Heart rate and blood pressure
Systemically, decrease mean BP via vasodilation (β2) and increased HR (β1) Increased Pulse pressure.

6 Effect of Norepinephrine on Heart rate and blood pressure
Exercise: Effect of norepinephrine after pre-tretment with atropine.

7 Effect of Epinephrine on Heart rate and blood pressure
Dose dependent effects Low dose: β1 ,β2 stimulation. High dose: α1, β1 (β2). Β2 specific effects: Smooth muscle relaxation. Metabolic effects: Increased glycogenolysis Increased gluconeogenesis Increased mobilization and use of fat. Exercise: Effect of epinephrine after pre-treatment with α1 blocker.

8 Effect of an unknown drug (R) on Heart rate and blood pressure
NBME Step1: Go to working section and write Receptor affections for each of drugs given in the choices ---interpret as the drug R will essentially work by using any of those receptors Step2 :What does the drug R do in BP &HR in control tracing? ------Match those effects with the drug from working section in lite of their receptor affection if more than 1 option looks correct move on to next experiment. Step3:Visit each experiment (R + Blocker) and ask 2 Qs. 1.Does the blocker changes drug response in anyway? (compare with control) interpret as if R + Blocker blocks a response caused by drug R meaning that drug R when given alone will produce that response (blocker can not produce any response by its own. It can only block an agonist response.) 2.In +ce of blocker can the drug still do some changes? (compare baseline/pre t/t vs drug effect in the same tracing) R is A. epinephrine B.norepinephrine C. phenylephrine D. isoproterenol E. terbutaline

9 Effect of an unknown drug (U) on Heart rate and blood pressure
NBME

10 Effect of an unknown drug (S) on Heart rate and blood pressure
NBME

11 Effect of an unknown drug (H) on Heart rate and blood pressure
NBME

12 Effect of an unknown drug (R) on Heart rate and blood pressure
NBME

13 Effect of an unknown drug (R) on Heart rate and blood pressure
NBME Drug H is Isoprotenol Epinephrine. Norepinephrine Phenylephrine Tyramine

14 Effect of an unknown drug (R) on multiple body parameters
NBME Drug X and Y are, respectively Isoproterenol and propranolol Epinephrine and phenoxybenzamine Norepinephrine and phentolamine Terbutaline and phenylephrine. Acetylcholine and hexamethonium

15 Effect of an unknown drug (R) on Heart rate and blood pressure
Effect of an unknown drug (R) on multiple body parameters NBME

16 Effect of unknown drugs on Heart rate and blood pressure in vitro
NBME

17 2. Releaser / indirectly acting drug 3. Muscarinic receptor blocker
NBME Horner's syndrome is a clinical syndrome caused by damage to the sympathetic nervous system. PAMELa" for Ptosis, Anhidrosis, Miosis, Enophthalmos and Loss of ciliospinal reflex. Lesions First-order neuron disorder: Central lesions that involve the hypothalamospinal pathway (e.g. transection of the cervical spinal cord). Second-order neuron disorder: Preganglionic lesions (e.g. compression of the sympathetic chain by a lung tumor). Third-order neuron disorder: Postganglionic lesions at the level of the internal carotid artery (e.g. a tumor in the cavernous sinus). lesion of the post-ganglionic sympathetic innervation of the right eye. 1. Alpha 1 agonist 2. Releaser / indirectly acting drug 3. Muscarinic receptor blocker 4. Alpha receptor blocker

18 Baroreceptor Reflex  BP = SNS;  PSNS  BP = SNS;  PSNS

19 Pretreatment with which drug will amplify the tachycardia produced by the baroreflex arc illustrated in the previous slide when an experimental subject is given an intravenous injection of histamine? Botulinum toxin Diphenydramine Hexamethonium Metoprolol Physostigmine Answer: E Amplifies response at ganglia

20 Baroreceptor Reflex BP (mmHg) SNA (Units) PSNA (Units) HR (bpm)
NBME Histamine Phenylephrine BP (mmHg) SNA (Units) PSNA (Units) HR (bpm) Time (minutes)

21 Pretreatment with which of the following will block the decrease in heart rate shown in the preceding slide when an intravenous injection of phenylephrine is given to an experimental subject? Metoprolol Phenelzine Physostigmine Prazosin Reserpine Answer: D Blocks alpha-1 receptors

22 Predicting Responses Epi reversal β1 & β2 β 1, β 2, & α 1 β 1, & α1
NBME β1 & β2 Epi reversal β 1, β 2, & α 1 β 1, & α1

23 Stimulation of which receptor is responsible for the slight pressor response seen on the preceding slide when norepinephrine is injected intravenously into an experimental subject pretreated with an alpha blocker? Alpha1 Alpha2 Beta1 Beta2 NicotinicN Answer: C Increases cardiac output

24 Heart Rate Blood Pressure ACH (2 mg) ACH (50 mg)
NBME Heart Rate Blood Pressure Look at BP 1st ACH (2 mg) Low dose ACH (50 mg) Intermediate dose (Atropine: Muscarinic Receptor Antagonist) ACH (50 mg) ACH (5 mg) High dose (Hexamethonium: Neuronal Nicotinic Receptor Antagonist) ACH (5 mg)

25 Which drug will block the pressor response illustrated on the preceding slide when 5 mg of ACh was given to an experimental subjects pretreated with atropine? Butoxamine Cocaine Metoprolol Physostigmine Prazosin Answer: E Blocks alpha-1 receptors


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