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The following message was posted to: PharmPK
Dear Colleagues,
Same dose of two different formulations of a drug was
given to the animals. Theoretically, this dose should
have given plasma concentration of ~1050 ng/mL at time
zero. The summary of PK profile is shown below:
Formulation 1 Profile A= Mono-exponential, C5min =1000
ng/mL, C1h = 800 ng/mL
Formulation 1 Profile B = Bi-exponential, C5min =1000
ng/mL, C1h = 80 ng/mL
Formulation 2 Profile = Bi-exponential, C5min =100
ng/mL, C1h = 10 ng/mL
Terminal phase of all three cases mention below are
parallel and yield similar half-life.
AUC for formulation 1 Profile A was 5 times greater
than AUC for formulation 1 Profile B and 100 times
greater than AUC for formulation 2 (AUC F1A > AUC F1B
> AUC F2).
Vz for AUC F1A was 4 times lower than Vz of AUC F1B
and 400 times lower than Vz of AUC F2. Similar trend
but different result was observed for Vss.
Vz was obtained through non-compartmental analysis
using the following equation: Vz = Dose / (lz *
AUCinf) so if the dose and lz are the same for all
three cases and difference is in AUC why the magnitude
of difference in Vz (100X) between F1B and F2 is not
reflective/proportional to magnitude of changes in AUC
(20X). Any comments?
Rostam
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The following message was posted to: PharmPK
Dear Rostam,
Were these formulations include some type of a drug
carrier (e.g. liposomes etc. ) ?
Some times when the drug is loaded on a carrier, the
distribution characteristics of the free drug is
altered to follow the distribution characteristics of
the carrier system
Regards
Mohsen Hedaya, Pharm.D., Ph.D.
College of Pharmacy
Tanta University
Tanta - Egypt
Phone: +20 10 176 8641 +20 40 333 1779
Fax: +20 40 334 8643 e.mail: mhedaya.at.e-pharmacokinetics.com
Web site: www.e-pharmacokinetics.com
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