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Re: Population PKPD using hair drug concentration

From: Sînziana Cristea <sanziana.cristea>
Date: Fri, 12 Jun 2015 15:54:57 +0100

Dear Bernard,

I don't know if you only have data collected from the hair on the scalp or
also from other parts of the body. If so, I think that you should try to
distinguish between body hair and scalp hair (maybe using covariates) since
they have different growth rates and so your drug could be eliminated
faster from the hair on the scalp (barber shop) compared to the hair on
your arm, for example.

Good luck and I am looking forward to the outcome.

Best regards,
Sinziana Cristea

*Research Associate *Simcyp Limited

On 12 June 2015 at 14:54, Leonid Gibiansky <lgibiansky

> Dear Bernard,
> This looks like really interesting problem. Based on the idea that it
> should be a long delay, I would start with the transit compartment model
> (you can google for the references on this type of models) with the input
> from the plasma compartment. The last compartment will represent a barber
> shop. The number of transit compartment can be increased until you get a
> sufficiently long delay. Observation compartment can be either the last
> one, or the sum of several, depending on how measurements are done (at a
> particular hair length, or by grinding the hair together before
> measurement). Depending on whether hair can eliminate the drug (or it
> happens only in the barber shop), hair clearance can be assigned to all or
> only to the last of those transit compartments.
> It could be that a simple effect compartment model with a very slow ke0
> could describe it as well but you should be able to see it by increasing or
> decreasing the number of transit compartments.
> Regards,
> Leonid
> --------------------------------------
> Leonid Gibiansky, Ph.D.
> President, QuantPharm LLC
> web:
> e-mail: LGibiansky at
> tel: (301) 767 5566
> On 6/12/2015 8:56 AM, Bernard Ngara wrote:
>> Dear all
>> I am a working on a study that measures both short and long term
>> exposure to drug using plasma and hair drug concentration. What
>> methods can I use to model hair drug concentration. You can give
>> references so that I can read.
>> Thanks once again.
>> Regards

Received on Fri Jun 12 2015 - 10:54:57 EDT

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