title: Formulation and characterization of poly(ethylene glycol)-based, 5-aminolevulinic acid-loaded solid-dosage forms intended for photodynamic and photodiagnostic methodologies in the colorectal region.
abstract: Aminolevulinic acid-loaded, poly(ethylene glycol) disks prepared using three molecular weights (1000, 6000, and 10,000) were shown to be of potential for rectal administration as part of photodynamic and photodiagnostic colorectal procedures. The disk-shaped delivery system was mechanically robust, as judged by friability measurements. Calorimetric analysis confirmed that low concentrations of ALA (1% w/w) were dispersed completely throughout the PEG matrix, but higher concentrations (5% w/w and 10% w/w) formed crystalline suspensions. The molecular weight of the PEG determined the melting temperature, with PEG 1000 being suitable for melting around body temperature. The drug release kinetics were shown to be a function of both molecular weight and drug loading. Although the higher molecular weight PEG disks were resistant to surface erosion arising from an aqueous receptor phase, this effect was counterbalanced by more rapid and complete release when the ALA loading was increased. The lowest loading used (1% w/w) produced incomplete release, often not exceeding 30% of the total amount of drug. Results suggest that this simple formulation containing ALA can be administered directly to the colorectal area and is a feasible alternative to peroral dosing of ALA.
authors.affiliation: School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Rd, Belfast BT9 7BL, UK.
authors.forename: Paul A
authors.initials: PA
authors.lastname: McCarron
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Andrews
authors.forename: Desmond I J
authors.initials: DI
authors.lastname: Morrow
authors.forename: A David
authors.initials: AD
authors.lastname: Woolfson
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Donnelly
mesh_terms: D000622:Aminolevulinic Acid / Q000737:chemistry*; D004339:Drug Compounding; D016503:Drug Delivery Systems; D006801:Humans; D007410:Intestinal Diseases / Q000175:diagnosis / Q000188:drug therapy; D007420:Intestine, Large; D008970:Molecular Weight; D010778:Photochemotherapy / Q000295:instrumentation* / Q000379:methods; D017319:Photosensitizing Agents / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D013488:Suppositories / Q000737:chemistry*
chemical_list: D017319:Photosensitizing Agents; D013488:Suppositories; D011092:Polyethylene Glycols; D000622:Aminolevulinic Acid