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Amylose coated pellets for colon-specific drug delivery

Milojevic, Snezana; (1993) Amylose coated pellets for colon-specific drug delivery. Doctoral thesis (Ph.D.), University College London (United Kingdom). Green open access

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Drug targeting to the colon may be possible by using a coating comprising amylose in glassy form. Amylose is a natural polysaccharide, in this case extracted from pea starch, and possesses the ability to form films through gelation. Its gel microstructure has been found to be resistant to pancreatic a-amylase but is digested by enzymes of colonic microflora origin. Amylose coatings swell in water, becoming porous and thus allowing drug release under simulated gastro-intestinal conditions. Incorporation of other polymers into the amylose film, to control the swelling of amylose has provided a solution to this problem. A range of coating materials (cellulose based polymers and acrylate based copolymers) were assessed of which a commercially available ethylcellulose (Ethocel®) was found to suppress amylose swelling. With additional thermal treatment of the coat, premature in vitro drug release was prevented even after storage of the product for one year. The in vitro digestion of various coated pellets under simulated gastro-intestinal tract conditions (using commercially available pepsin and pancreatin powder) was determined and has demonstrated the resistance of the amylose/Ethocel® mixture to such conditions over a period of 12h. Coated pellets were further evaluated in a batch culture fermenter (simulated colon conditions) which contained mixed faecal bacteria. The in vitro release of 5-aminosalicyhc acid from coated pellets in the fermenter system was studied. The in vivo performance of amylose/Ethocel coated pellets in 8 healthy human volunteers was evaluated using 13CO2 excretion in breath after ingestion of 13C-labelled glucose (incorporated into the pellets) and measured using mass spectrometry. Inert lactose pellets containing amberlite resin and of the same diameter and density as the glucose were labelled with 99mTc to provide a marker to follow gastro-intestinal transit. Gamma scan photographs showed the mean arrival time of 99Tc labelled pellets at the caecum was 3.5h (range 2.50-4.75h). 13CO2 in breath was not detected until 3.7h post dosing and did not become significant (1% recovery) until 6.4h. 13CO2 was not found in breath before pellets had reached the caecum and there was a delay of 2.9h between arrival in the caecum and significant (1%) breakdown of the pellets. enrichment in breath increased linearly for up to 15h and this was still evident 24h after administration of pellets, indicating a gradual release of glucose as the pellets passed through the colon.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Amylose coated pellets for colon-specific drug delivery
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: (UMI)AAI10104161; Health and environmental sciences; Drug targeting
URI: https://discovery.ucl.ac.uk/id/eprint/10109576
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