USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 Register FAQs Members List Search Today's Posts Mark Forums Read

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

#1
03-31-2013
 USMLE Forums Scout Steps History: Not yet Posts: 40 Threads: 22 Thanked 3 Times in 3 Posts Reputation: 13

Can't remember if this was posted but here goes:

At a target concentration of 7.5 mg/L of theophyline is required by a 60kg patient. What is the loading dose given the following:
Vd= 0.5 L/kg
Cl= 0.04 L/kg/hr
t1/2= 9.3 hrs

#2
03-31-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 824 Threads: 66 Thanked 465 Times in 298 Posts Reputation: 475

LD=CpxVd/F
LD=7.5x0.5=3.75mg/Kg=225mg
__________________
Everything is possible for him who believes (MARK 9:23)
245/247/passed on 1st attempt/223/2mos Obsie /3 US LORS/visa not needed/2008 grad
#3
03-31-2013
 USMLE Forums Veteran Steps History: 1 + CS Posts: 209 Threads: 18 Thanked 112 Times in 75 Posts Reputation: 122

lets assume bio-availability is 1

so

according to weight 3.75 x 60 = 225 mg
__________________
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.

#4
03-31-2013
 USMLE Forums Veteran Steps History: 1 + CS Posts: 209 Threads: 18 Thanked 112 Times in 75 Posts Reputation: 122

Quote:
 Originally Posted by MedicalExaminer Add options LD=CpxVd/F LD=7.5x0.5=3.75mg/Kg=225mg

thasts right but am confused here pls explain this question one for me;

Q:if drug is known to be distributed into TBW, what dose (mg) is needed to obtain an initial plasma level of 5mg/L in patient weighing 70kg?

a)210
b)150
c)110
d)50
e)35
__________________
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.
#5
03-31-2013
 USMLE Forums Veteran Steps History: 1 + CS Posts: 209 Threads: 18 Thanked 112 Times in 75 Posts Reputation: 122

Quote:
 Originally Posted by neha_subh thasts right but am confused here pls explain this question one for me; Q:if drug is known to be distributed into TBW, what dose (mg) is needed to obtain an initial plasma level of 5mg/L in patient weighing 70kg? a)210 b)150 c)110 d)50 e)35
A)210

since the patient weighs 70kg and 60% TBW,he has 42 L (70L X 60%) Of TBW.

NOW
LD = Vd x Cp

LD = 42L X 5mg/L = 210mg
__________________
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.
 The above post was thanked by: rathoreprajay (03-08-2017)
#6
03-31-2013
 USMLE Forums Veteran Steps History: Step 1 Only Posts: 283 Threads: 35 Thanked 206 Times in 115 Posts Reputation: 216

Quote:
 Originally Posted by OMGStep Can't remember if this was posted but here goes: At a target concentration of 7.5 mg/L of theophyline is required by a 60kg patient. What is the loading dose given the following: Vd= 0.5 L/kg Cl= 0.04 L/kg/hr t1/2= 9.3 hrs

= 7.5 mg/L X 0.5 L/Kg / 1

= 3.75 mg / Kg

Now times this by 60 Kg to get rid of Kg.

3.75 mg/Kg X 60 Kg

= 225 mg is my answer. Don't know if I'm right or wrong.
#7
07-17-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 592 Threads: 92 Thanked 198 Times in 129 Posts Reputation: 208

Quote:
 Originally Posted by neha_subh answer of that question is: A)210 This is loading dose question. since the patient weighs 70kg and 60% TBW,he has 42 L (70L X 60%) Of TBW. NOW LD = Vd x Cp LD = 42L X 5mg/L = 210mg
==========
Please Nena help me with this one, im so confused
why do you multiply 70 by the porcentage of water?
please someone explain, im stuck here

 Tags Pharmacology-, Step-1-Questions

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
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.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
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.