Effect of FITC-dextran molecular weight on its release from floating cetyl alcohol and HPMC tablets.
The release mechanism of high molecular weight fluorescein isothiocyanate dextrans (FITC-dextrans) from HPMC hydrogel matrices was studied. An anomaly was noted in the release behaviour of a series of high molecular weight FITC-dextrans from a tablet formulation designed to float in stomach contents. The tablets contained sodium bicarbonate and hydroxypropylmethyl cellulose (HPMC) in a cetyl alcohol matrix. When hydrated in an acid medium, this tablet consisted of a mixed solid with a viscous surface layer containing carbon dioxide bubbles through which the active ingredient (FITC-dextran) was released into the aqueous environment. However, it was observed that, above a critical molecular weight (approx. 65 kDa), the FITC-dextran was only released into the medium by an erosion-type mechanism, whereas, below this value, both diffusion and erosion processes took place. The key constraint appeared to be the apparent gel pore-size of the hydrated HPMC that was approximately 12 nm in diameter, irrespective of the molecular weight of the HPMC samples evaluated. It was concluded that FITC-dextran release was controlled by both FITC-dextran molecular weight and the HPMC hydrogel structure.
Xu
G
G
Institute for Tuberculosis Research, College of Pharmacy, University of Illinios at Chicago, 60612, USA.
Groves
M J
MJ
D003911:Dextrans / Q000493:pharmacokinetics*; D005233:Fatty Alcohols / Q000737:chemistry / Q000493:pharmacokinetics*; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007785:Lactose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics*; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics*; D008970:Molecular Weight; D010078:Oxazines; D013607:Tablets
D003911:Dextrans; D005233:Fatty Alcohols; D010078:Oxazines; D013607:Tablets; C015219:fluorescein isothiocyanate dextran; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008747:Methylcellulose; C005031:cetyl alcohol; C071191:MK 458; D016650:Fluorescein-5-isothiocyanate; D007785:Lactose