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hello all,
could anyone explain how can i calculate MAT (mean absorption time)
from the cumulative amounts curve or from the area over the curve ?
is there is any formula other than MAT = MRT oral - MRT iv ?
thanks in advance
kabja
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The following message was posted to: PharmPK
Dear Khaled,
these are some examples:
Assuming 1st-order kinetics, MAT can also be estimated from ka
(absorption rate constant) after oral dosing as such: ka = 1/MAT
or
absortption t1/2 =0.693 x MAT
In the case when drug absorption is a zero-order process:
MAT = T/2 (T is the time over which absorption takes place)
You can get MAT from MRT po and MRT iv estimated from their
corresponding AUMCs and AUC values and apply them to the formula you
indicated (MAT = MRT po - MRT iv):
MRT po = AUMC po/AUC po and
MRT iv = AUMC iv/AUC iv
MRT iv = 1/k (one-compartment model, iv, and k is the elimination rate
constant) MRT po = 1/ka + 1/k (one-compartment model, po)
or you can relate your MRT to Vss as such: MRT = Vss/Cl
I hope these are helpful
Kassem Abouchehade
PhD Candidate
PK-PD Research/Sessional Instructor
School of Pharmacy
Health Science Centre
Memorial University of Newfoundland
St. John's, NL. A1B 3V6 CANADA
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The following message was posted to: PharmPK
Kabja
Please understand that it's not a matter of formulae. You should read
in any PK textbook the chapter for Mean Time Parameters. Before doing
any calculation it's crucial that you understand that Mean Absorption
Time, or better said Mean Arrival Time, corresponds to the time on
average that drug molecules spend prior absorption, or in other
words, the residence time of those molecules 'outside' the absorption
'site'.
Also the only area that you'll be able to calculate is the Area
""Under"" the Curve.
I hope this helps.
Luis
--
Luis M. Pereira, Ph.D.
Assistant Professor, Biopharmaceutics and Pharmacokinetics
Massachusetts College of Pharmacy and Health Sciences
179 Longwood Ave, Boston, MA 02115
Phone: (617) 732-2905
Fax: (617) 732-2228
Luis.Pereira.-at-.bos.mcphs.edu
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