Pharm Question

Discussion in 'Medical Students - MD' started by Pythagoras, Dec 4, 2005.

1. Pythagoras Senior Member 7+ Year Member

Joined:
May 13, 2003
Messages:
269
0
I've been trying to figure this out for a while and i feel like an idiot for not being able to get the right answer, any help would be appreciated.

A new aminoglycoside antibiotic (5mg/kg) was infused IV over 30 min to a 70kg volunteer. The plasma concentration of the drug was measured at various times after the end of the infusion, as recorded below.

Time after dosing stopped (hr) Plasma concentration (ug/mL)
0.0 18.0
0.5 10.0
1.0 5.8
2.0 4.6
3.0 3.7
4.0 3.0
5.0 2.4
6.0 1.9
8.0 1.3

The elimination half life is ~3.5 hrs

The apparent volume of distribution is approximately?

The total body clearance is approximately?

any help would be appreciated. thanks

2. tupac_don Senior Member 5+ Year Member

Joined:
May 16, 2004
Messages:
881
3

This is what you do, find ke (ke=ln(5.8/1.3)/t8 - t1 Use values for 1hr after infusion and 8 hrs after end of infusion.

When you have ke you can double check t1/2=.693/k

Cmax=5.8/e-ke * t1 (0.5), then Cmin=Cmax (e-(ke*T-t (use 7.5))

For Vd= Dose/Cmax - Cmin

CrCl= Vd * ke * 1000/60

Good luck.

We’ve been on the Internet for over 20 years doing just one thing: providing career information for free or at cost. We do this because we believe that the health education process is too expensive and too competitive.

We believe that all students deserve the same access to high quality information. We believe that providing high quality career advice and information ensures that everyone, regardless of income or privilege, has a chance to achieve their dream of being a doctor.