Pharm Question

[Pythagoras]

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

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[tupac_don]

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

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.