- On 11 May 2006 at 14:25:48, "Dario Salerno" (dsalerno.at.rtc.it) sent the message

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The following message was posted to: PharmPK

Dear PKusers,

I want specify better my doubt.

The objective of my study is to investigate the toxicity/

toxicokinetic of a test item in dogs after daily intravenous infusion

for 24 hours for a 4 week treatment period.

Blood will be sampled after the first 24 hrs of infusion (on the

morning of day 2) and then after 14 days of infusion (on the morning

of day 15) and then on day 29. No sampling will be perfomed after the

end of infusion.

My question is if it is possible to calculate the STD parameters in

this type of administration? Is it correct to determinate the t 1/2

of a drug if given by continous infusion?

So the following definitions for the PK parameters could be write in

the study protocol?

The toxicokinetic analysis will be conducted according to a standard

non-compartmental analysis.

The following parameters will be calculated:

Cmax : maximum observed plasma concentration

tmax : time to Cmax

Clast : The concentration value obtained at sampling time Tlast.

Tlast : The last sampling time at which a quantifiable

concentration is found.

AUClast : The area under the plasma concentration versus time curve

up to sampling timeTlast, calculated by linear trapezoidal rule.

t 1/2 : elimination half-life

thank you very much.

please help me its urgent.

Dario Salerno, Chem.Pharm.D.

Study Director - On 12 May 2006 at 16:30:53, "Hans Proost" (j.h.proost.-at-.rug.nl) sent the message

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Dear Dario,

If I understand you correctly, you will infuse the drug over 28 days,

and

take samples after 1 day, 14 days and 28 days. This will not allow

you to

calculate any of the PK parameters you listed. If the half-life is

less than

about 6 hours, the expected concentration at all time points is the

same,

and clearance can be calculated, but none of the other PK parameters.

If the half-life is longer, you might get a crude estimate of half-

life from

the increase of the concentration, but this is not the preferred

method to

estimate half-life.

Best regards,

Hans Proost

Johannes H. Proost

Dept. of Pharmacokinetics and Drug Delivery

University Centre for Pharmacy

Antonius Deusinglaan 1

9713 AV Groningen, The Netherlands

tel. 31-50 363 3292

fax 31-50 363 3247

Email: j.h.proost.at.rug.nl - On 16 May 2006 at 13:35:08, Andrew Sutton (asutton.-a-.gcpl.co.uk) sent the message

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Colleagues:

May I ask Dario Salerno for the justification of a study that

delivers an

infusion 24 hours a day for 28 days to a dog? Apart from questions

relating to animal welfare I am surprised that there is a real

possibility

of altered kinetics after such a long period if Pk is the aim of the

study

(and not toxicology).

Thanks

Andrew Sutton

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