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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

 The ileum

It is the terminal part of the small intestine.

The pH is about 7, with the distal part as high as 8.

Due to the presence of bicarbonate secretion, acid drugs will dissolve.

Bile secretion helps to dissolve fats and hydrophobic drugs.

The ileocecal valve separates the small intestine from the colon.

The colon lacks villi and has limited drug absorption also, because of:

• The more viscous and

• Semisolid nature of the lumen contents.
The colon is lined with mucin that functions as lubricant and protectant.

Bacteria, which are mainly localized within the colonic region of the GIT, also secrete

enzymes which are capable of a range of reactions. These enzymes have been utilized

when designing drugs or dosage forms to target the colon.

Sulphasalazine is a prodrug of 5-aminosalicylic acid linked via an azo bond to

sulphapyridine. The sulphapyridine moiety makes the drug too large and hydrophilic

to be absorbed in the upper GIT, and thus permits its transport intact to the colonic

region, where the bacterial enzymes reduce the azo bond and release the active drug

for local action in colonic diseases such as inflammatory bowel disease.

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