In vivo determination of the time and location of mucoadhesive drug delivery systems disintegration in the gastrointestinal tract.
OBJECTIVE
The objective of this study was to use magnetic resonance imaging (MRI) to detect the time when and the location at which orally delivered mucoadhesive drugs are released.


METHODS
Drug delivery systems comprising tablets or capsules containing a mucoadhesive polymer were designed to deliver the polymer to the intestine in dry powder form. Dry Gd-DTPA [diethylenetriaminepentaacetic acid gadolinium(III) dihydrogen salt hydrate] powder was added to the mucoadhesive polymer, resulting in a susceptibility artifact that allows tracking of the application forms before their disintegration and that gives a strong positive signal on disintegration. Experiments were performed with rats using T(1)-weighted spin-echo imaging on a standard 1.5-T MRI system.


RESULTS
The susceptibility artifact produced by the dry Gd-DTPA powder in tablets or capsules was clearly visible within the stomach of the rats and could be followed during movement towards the intestine. Upon disintegration, a strong positive signal was unambiguously observed. The time between ingestion and observation of a positive signal was significantly different for different application forms. Quantification of the remaining mucoadhesive polymer in the intestine 3 h after observed release showed significant differences in mucoadhesive effectiveness.


CONCLUSIONS
MRI allows detection of the exact time of release of the mucoadhesive polymer in vivo, which is a prerequisite for a reliable quantitative comparison between different application forms.
Kremser
Christian
C
Department of Radiology, Innsbruck Medical University, A-6020 Innsbruck, Austria. christian.kremser@i-med.ac.at
Albrecht
Karin
K
Greindl
Melanie
M
Wolf
Christian
C
Debbage
Paul
P
Bernkop-Schnürch
Andreas
A
D000180:Acrylic Resins / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000284:Administration, Oral; D000818:Animals; D016477:Artifacts; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics*; D016503:Drug Delivery Systems; D019793:Fluorescein / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019786:Gadolinium DTPA / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007413:Intestinal Mucosa / Q000187:drug effects*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
D000180:Acrylic Resins; D003287:Contrast Media; C030312:calcium polycarbophil; D019786:Gadolinium DTPA; D019793:Fluorescein