# PharmPK Discussion - Mean Absorption Time

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• On 2 Sep 2005 at 19:29:09, khaled abduljalil (khal_assa.at.yahoo.com) sent the message
`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 advancekabja`
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• On 3 Sep 2005 at 06:23:49, "Kassem Abouchehade" (kassem.-at-.hebert.pharm.mun.ca) sent the message
`The following message was posted to: PharmPKDear 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/MATorabsortption t1/2 =0.693 x MATIn 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 theircorresponding AUMCs and AUC values and apply them to the formula youindicated (MAT = MRT po - MRT iv):MRT po = AUMC po/AUC po  andMRT iv = AUMC iv/AUC ivMRT iv = 1/k (one-compartment model, iv, and k is the elimination rateconstant) MRT po = 1/ka + 1/k (one-compartment model, po)or you can relate your MRT to Vss as such:  MRT = Vss/ClI hope these are helpfulKassem AbouchehadePhD CandidatePK-PD Research/Sessional InstructorSchool of PharmacyHealth Science CentreMemorial University of NewfoundlandSt. John's, NL. A1B 3V6  CANADA`
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• On 6 Sep 2005 at 10:30:41, "Pereira, Luis" (Luis.Pereira.-at-.bos.mcphs.edu) sent the message
`The following message was posted to: PharmPKKabjaPlease understand that it's not a matter of formulae. You should readin any PK textbook the chapter for Mean Time Parameters. Before doingany calculation it's crucial that you understand that Mean AbsorptionTime, or better said Mean Arrival Time, corresponds to the time onaverage that drug molecules spend prior absorption, or in otherwords, 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 PharmacokineticsMassachusetts College of Pharmacy and Health Sciences179 Longwood Ave, Boston, MA  02115Phone: (617) 732-2905Fax: (617) 732-2228Luis.Pereira.-at-.bos.mcphs.edu`
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