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Does any one know about the absorption site for fluoroquinolone
compounds eg norfloxacin. As norfloxacin is an ampholytic compound
should the pH influence the absorption rate/site. To which level the
drug absorption could be reduced in the presence of metallic antiacid.
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[Two replies - db]
From: "Bruce CHARLES"
Organization: School of Pharmacy
Date: Sun, 19 Apr 1999 15:15:25 +1000
Subject: Re: PharmPK Norfloxacin REPLY
X-Confirm-Reading-To: "Bruce CHARLES"
Presumably it is abosrbed in the upper duodenum like most drugs.
Regarding the influence of metal cations this is a potentially serious
interaction. See our paper (J Pharm Sci 85(8);803-809;1996) on
the in vitro complexation chemistry of a number of pharmaceutical
metal cations, and reduction in oral bioavilability (in dogs) as a
function of magnitude of the (log) stability constant and
the concentration of cation.
Bruce CHARLES, PhD
School of Pharmacy
The University of Queensland
Brisbane, QLD Australia 4072
TEL: +61 7 336 53194
FAX: +61 7 336 51688
Date: Mon, 19 Apr 1999 09:03:01 -0700
From: "David Nix, Pharm D."
Organization: College of Pharmacy
Subject: Re: PharmPK Norfloxacin
Fluoroquinolones are absorbed primarily in the upper small intestines.
There are a number of studies (esp. with ciprofloxacin) where site
specific administration was used to study absorption. In general, the
bioavailability decreases when the drug was administered in the lower
jejunum or ileum. The solubility of fluoroquinolones is reduced at pH
values near the isoelectric points (about 7.0 to 7.5). When gastric
acid is suppressed there is a tendency toward decreased
bioavailability. With ciprofloxacin, concurrent administration of H-2
antagonists causes a trend toward decreased AUC (not significant). We
showed a significant decrease in enoxacin AUC when H-2 antagonist was
titrated to maintain gastric pH > 5 (Clin Pharmacol Ther
The specific nature of the absorption process is not known. It is
possible that FQ's may be absorbed as a chelate with a divalent cation
or by some factilitated process.
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