Kinetics question

[lazydazy]

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I'm reviewing kinetics for my new job. Is there any difference between the below equations for calculating ke? Any reason you want to use one vs. the other? I understand that you can use the first eq. once you have levels to calculate a patient-specific ke. The ke is dependent on Vd and Cl so the third equation can be used to determine ke. The fourth equation takes into account population parameters from studies, which this eq. can be used to determine an initial ke for initial dosing.

Can you use any of the equations to calculate ke? I mean, eq. 2-4 are generally used for initial ke determination then you can calculate the pt specific ke once you have concentrations, correct?

Ke = ln [(Cp1/Cp2)] /Δt

Ke = (0.693)/t½

Ke= Cl/Vd

Ke= 0.0024 x CrCl + 0.01

Just trying to get it all straight...thanks!

 

[Its Z]

You're missing

LD = Vd x Cmax

 

[New Bee]

I'm reviewing kinetics for my new job. Is there any difference between the below equations for calculating ke? Any reason you want to use one vs. the other? I understand that you can use the first eq. once you have levels to calculate a patient-specific ke. The ke is dependent on Vd and Cl so the third equation can be used to determine ke. The fourth equation takes into account population parameters from studies, which this eq. can be used to determine an initial ke for initial dosing.

Can you use any of the equations to calculate ke? I mean, eq. 2-4 are generally used for initial ke determination then you can calculate the pt specific ke once you have concentrations, correct?

Ke = ln [(Cp1/Cp2)] /Δt

Ke = (0.693)/t½

Ke= Cl/Vd

Ke= 0.0024 x CrCl + 0.01

Just trying to get it all straight...thanks!

Why are you interested in calculating ke? Usually it is the other way around, i.e. you have the ke and want to calculate the terminal elimination half-life. The last equation is a population-derived equation that is drug specific.

 

[npage148]

The first 3 are NCA derived forms of ke. The first 1 uses the terminal slope and the third uses C0 and AUC. The second is just the first upside down. The 4th is drug specific for gent, a renally excreted drug.

ke is really a composite term comprised of Cl and V. Where these 2 parameters are true PK parameters we should be interested in