elimination half life of the drug: - 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 03-30-2013
neha_subh's Avatar
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 18
Thanked 111 Times in 74 Posts
Reputation: 121
Drug elimination half life of the drug:

10 volunteers in a drug study are administered I/V 500mg of an drug. in a 24 hrs period blood levels are measured.mean data shown belown:

TIME (hr):------0---1---2---3---6-----9--12--18--24


plasma level--24-23--22--21--18--15--12--6----0
(mg/ L)

from these data elimination of the drug is which of the folowing??

a') 1hr
b) 6hrs
c) 12hrs
d) 24hrs
e) has no fixed value
__________________
lets kick some doors open and help each other to reach our destinies
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
The above post was thanked by:
Doctor Ali (03-30-2013)



  #2  
Old 03-30-2013
USMLE Forums Guru
 
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 155 Times in 84 Posts
Reputation: 165
Default

0, 1, 2, 3..

24, 23, 22...

looks like zero order kinetics here. and clearance is constant no matter what. so is it 24 hours? i may have to rethink this one.

D?


what am i talking about!!! in Zero order, Clearance is NOT constant. this has to be a 1st order, give me a little more time on this.

Last edited by ReggieMiller; 03-30-2013 at 05:00 AM.
Reply With Quote Quick reply to this message
  #3  
Old 03-30-2013
nandish_m's Avatar
USMLE Forums Addict
 
Steps History: Not yet
Posts: 117
Threads: 5
Thanked 59 Times in 40 Posts
Reputation: 69
Default

i think 1hour is the ans..
constant amout 1mg/L is eliminated per hour
Reply With Quote Quick reply to this message
  #4  
Old 03-30-2013
USMLE Forums Guru
 
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 155 Times in 84 Posts
Reputation: 165
Default

I don't know why, but for me, units are important here. what are the units for the answer choices?

it its asking for clearance, should it be in mg/min?

but its asking for elimination, so does that mean how long it takes the drug to be completely eliminated? because if that's the case, then it takes 24 hours for the levels to go from 24mg/L to 0mg/L (so regardless of zero or first order kinetics, the elimination of the drug occurs over a period of 24 hours.

i'm just confused by the units, because its in only TIME, i feel that its not asking for a rate.
Reply With Quote Quick reply to this message
  #5  
Old 03-30-2013
USMLE Forums Guru
 
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 155 Times in 84 Posts
Reputation: 165
Default

do you have the correct answer for this question?

i think i'm going to spend the rest of this day figuring out the first part of pharmacology, and then doing all the ANS! want to finally get the concepts down, and get this out of the way11
Reply With Quote Quick reply to this message
  #6  
Old 03-30-2013
neha_subh's Avatar
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 18
Thanked 111 Times in 74 Posts
Reputation: 121
Default corect answer is E)

Quote:
Originally Posted by ReggieMiller View Post
do you have the correct answer for this question?

i think i'm going to spend the rest of this day figuring out the first part of pharmacology, and then doing all the ANS! want to finally get the concepts down, and get this out of the way11
hey dont be panic,this question has gud option to choose it has not fixed value.
i marked it because i have not seen any constant amount has been eliminated, initialy i found constant amount eliminated after that i didnt found any constant amount elimination and nor it has fixed half life.so how can you say that it is zero order kinetic.

CORECT ANSWER IS E)

Explanation:
the question is asking for the half life of a given drug.
half life is defined as time required to decrease the remaining portion of drug in the body by 1/2 and remains constant irrespective of the Cp.

in this question the drug concntration decrease by 1mg/L/hour. the initial conc: is 24mg/L at time zero. 12hrs later the drug conc: dec: by 50% and is 12mg/L.

Based on definition of half life,drug conc: should b decrease by anothr 50% 12hrs later.
12hrs later or time 24hrs however the concentration is 0.

the elimination half life of the investigational drug therefore has no true fixed value.

kaplan asesment question.
__________________
lets kick some doors open and help each other to reach our destinies
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by neha_subh; 03-30-2013 at 07:41 AM.
Reply With Quote Quick reply to this message
The above post was thanked by:
Doctor Ali (03-30-2013), sami trailer (03-30-2013)
  #7  
Old 03-30-2013
USMLE Forums Scout
 
Steps History: 1 + CS
Posts: 47
Threads: 8
Thanked 12 Times in 10 Posts
Reputation: 22
Default

Quote:
Originally Posted by neha_subh View Post
hey dont be panic,this question has gud option to choose it has not fixed value.
i marked it because i have not seen any constant amount has been eliminated, initialy i found constant amount eliminated after that i didnt found any constant amount elimination and nor it has fixed half life.so how can you say that it is zero order kinetic.

CORECT ANSWER IS E)

Explanation:
the question is asking for the half life of a given drug.
half life is defined as time required to decrease the remaining portion of drug in the body by 1/2 and remains constant irrespective of the Cp.

in this question the drug concntration decrease by 1mg/L/hour. the initial conc: is 24mg/L at time zero. 12hrs later the drug conc: dec: by 50% and is 12mg/L.

Based on definition of half life,drug conc: should b decrease by anothr 50% 12hrs later.
12hrs later or time 24hrs however the concentration is 0.

the elimination half life of the investigational drug therefore has no true fixed value.

kaplan asesment question.
I think we are missing the point that it is a "mean" data of 10 volunteers. The elimination rates of different volunteers must be different from one another (ie, no fixed value) because thats the reason the mean values are not following either zero order or first order.
Reply With Quote Quick reply to this message
  #8  
Old 03-30-2013
USMLE Forums Guru
 
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 155 Times in 84 Posts
Reputation: 165
Default

Quote:
Originally Posted by docsdr View Post
I think we are missing the point that it is a "mean" data of 10 volunteers. The elimination rates of different volunteers must be different from one another (ie, no fixed value) because thats the reason the mean values are not following either zero order or first order.
but when plotted on an x and y axis, it is a straight line, which means first order kinetics!

i understand that it decreases by 1mg/L/hr.

so far, that makes sense.

but where is the question asking for the half life? zero order does not even have half lifes, i understand that. but i don't see anywhere where we are asked to find the half life. doesn't sound like a fair question to me.
Reply With Quote Quick reply to this message
  #9  
Old 03-30-2013
neha_subh's Avatar
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 18
Thanked 111 Times in 74 Posts
Reputation: 121
Smile

sorry dear, i dont know whether this question is good or not, i shared here because it was diferent from others questions.

this question is from kaplan asesment test.
__________________
lets kick some doors open and help each other to reach our destinies
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #10  
Old 03-30-2013
neha_subh's Avatar
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 18
Thanked 111 Times in 74 Posts
Reputation: 121
Default metric conversion of grams,miligrams,micrograms,millilietrs and liters

http://www.epic4health.com/mecoofgrmimi.html
__________________
lets kick some doors open and help each other to reach our destinies
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message
  #11  
Old 03-30-2013
USMLE Forums Guru
 
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 155 Times in 84 Posts
Reputation: 165
Default

Quote:
Originally Posted by neha_subh View Post
sorry dear, i dont know whether this question is good or not, i shared here because it was diferent from others questions.

this question is from kaplan asesment test.
would you mind copy/pasting the complete question stem? i just don't see how they assuemd we'd have to calculate the half life.
Reply With Quote Quick reply to this message
  #12  
Old 03-30-2013
neha_subh's Avatar
USMLE Forums Veteran
 
Steps History: 1 + CS
Posts: 209
Threads: 18
Thanked 111 Times in 74 Posts
Reputation: 121
Default

Quote:
Originally Posted by ReggieMiller View Post
would you mind copy/pasting the complete question stem? i just don't see how they assuemd we'd have to calculate the half life.
whatever i have posted that is the complete question and explanation of the answer.
__________________
lets kick some doors open and help each other to reach our destinies
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message



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
Calculate the Drug Half Life? venky2600 USMLE Step 1 Forum 1 08-10-2012 12:31 PM
Drug dose, half life, and efficacy adeelacheema USMLE Step 1 Forum 4 07-16-2012 03:30 AM
Drug half life usluipek USMLE Step 1 Forum 2 12-10-2011 05:22 PM
Calculated the half life for this drug? earthpole USMLE Step 1 Forum 7 04-01-2011 07:35 PM
Research Drug Half Life? Yallah USMLE Step 1 Forum 3 04-19-2010 07:43 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)