- On 7 Nov 2003 at 18:31:51, "Henri Merdjan" (hmerdjan.at.wanadoo.fr) sent the message

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The following message was posted to: PharmPK

Dear all,

Are you aware of any method to estimate the effective half-life for

accumulation by using single dose PK parameters?

I have tried using ln(2)*MRTiv as well as a "weighted" sum of half-lives

where the weights depend on the contribution of each phase to total

AUC. It

did not work. Can you help, please?

Let's keep it simple and assume an intravenous bolus dose, a

2-exponential

model, linear and time-invariant PK

Many thanks in advance,

Henri

Henri Merdjan

Consultant for the Life Science Industries

PK and PK/PD specialist

NewFreelance sarl

Paris, France

+33 (0)6 23 97 67 34

hmerdjan.-a-.wanadoo.fr - On 7 Nov 2003 at 15:40:40, (Anne.Paccaly.aaa.aventis.com) sent the message

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The following message was posted to: PharmPK

Dear Henri,

An approximation could be:

After single dose the R=AUCinf/AUCtau (R=accumulation ratio, tau is

whatever

intended dosing interval). You could then estimate the "effective

half-life"

using the equation

R=1/(1-e-ke*tau), t1/2 "effective" being 0.693/ke

Hope this helps

Anne Paccaly, Pharm.D.

Clinical Pharmacokinetics,DMPK,

Aventis, Bridgewater NJ

908-231 -2835 (Phone), 908-231-5933 (Fax)

E-mail:anne.paccaly.-a-.aventis.com

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