Which drug will increase the heart rate? - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-02-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 570 Times in 323 Posts
Reputation: 580
Drug Which drug will increase the heart rate?

Which drug would be expected to increase the heart rate in the absence of sympathetic or parasympathetic innervation?

a) Amphetamine
b) Atropine
c) Pindolol
d) Propranolol
e) Tyramine
Reply With Quote Quick reply to this message
The above post was thanked by:
587964 (08-02-2012)



  #2  
Old 08-02-2012
beka-CTS's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 763
Threads: 77
Thanked 1,370 Times in 349 Posts
Reputation: 1380
Default

Which drug would be expected to increase the heart rate in the absence of sympathetic or parasympathetic innervation?

a) Amphetamine
b) Atropine
c) Pindolol
d) Propranolol
e) Tyramine

Due to Intrinsic Sympathomimetic Activitiy, Acebutolol has it too.
__________________
Step 1 - 244 [✔] Step 2 CK - 246 [✔] Step 2 CS [✔] Step 3 - 228 [✔] Match [EMORY SOM] YOG: 2013, 4 Months of USCE University Hospital
Reply With Quote Quick reply to this message
  #3  
Old 08-02-2012
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 791
Threads: 76
Thanked 673 Times in 317 Posts
Reputation: 691
Default

B---atropine
Reply With Quote Quick reply to this message
 
  #4  
Old 08-02-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,039
Threads: 189
Thanked 570 Times in 323 Posts
Reputation: 580
Default correct answer :)

The answer is C) Pindolol

Pindolol is a partial agonist at β1- and β2-adrenergic receptors. In the presence of a full agonist (such as norepinephrine), pindolol behaves as a nonspecific β-adrenergic antagonist. In the absence of a full agonist, pindolol displays intrinsic sympathomimetic activity (ISA). Consequently, pindolol would stimulate β1 receptors and increase the heart rate in the absence of a full agonist.

As for atropine -Atropine is a competitive muscarinic receptor antagonist. Antagonists bind to a receptor but do not produce an effect (i.e., they have no intrinsic activity). In the absence of an agonist, they would produce no change in response. In the innervated heart, atropine would block acetylcholine-induced bradycardia and increase the heart rate.

So in other words because we are talking about the denervated heart, after blocking M receptors there wouldn't be no SANS dominance like in vivo conditions.
Reply With Quote Quick reply to this message
The above post was thanked by:
anomali (08-03-2012), RocketMD (08-14-2012)



Reply

Tags
Pharmacology-, Step-1-Questions

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fetal Heart Rate Interpretation! sneha89 USMLE Step 2 CK Forum 4 07-29-2012 06:18 PM
Calculating the heart rate in the EKG sana akbar USMLE Step 2 CK Forum 1 12-01-2011 10:54 AM
All-cause mortality rate, prevalence and case fatality rate question! Claus_CU USMLE Step 1 Forum 5 05-25-2011 06:38 PM
The effect of heart rate on systolic and diastolic pressures? eesfee USMLE Step 1 Forum 2 05-25-2011 12:24 PM
Why Digoxin decreases the heart rate? vrnda USMLE Step 1 Forum 8 05-06-2011 08:23 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)