Drug delivery to the colon

Abstract

The recent patent literature concerning drug delivery to the colon is reviewed. A variety of products are under development using either specialised drug coatings or specific devices that target drugs to the colon. The use of coatings that break down in response to microbial flora, change in pH or the permeation of water, herald promise. A number of devices that release drugs in response to changes in pressure, the passage of time or that have degradable tablet cores are also described. However, many of these devices are so complex that they may be uneconomic to manufacture. Colonic drug delivery devices that release drugs in response to microbial degradation are the most propitious, as they are simple and are less susceptible to inter-patient variability.

Colonic delivery of 4‐aminosalicylic acid using amylose–ethylcellulose‐coated hydroxypropylmethylcellulose capsules

“…Traditionally, enteric‐coated preparations, which disintegrate at neutral pH conditions, have been used to deliver drugs, including 4‐ASA, to the distal gut; 11–13 however, the colon specificity of such systems is known to be poor 14 ,. 15 This is not unduly surprising given the variable nature of the gastrointestinal tract, particularly in terms of pH and transit time, which makes colonic targeting via the oral route an exceedingly difficult proposition.…”

The role of excipients in determining the pharmaceutical and therapeutic properties of medicinal agents (Review)

“…Materials such as shellac and keratin were used in the past, though the passage of time saw the synthesis of a multitude of pH-sensitive polymers soluble at different pH values (cellulose acetate phthalate, which dissolves at pH values above 6, and hydroxypropylmethylcellulose phthalate, which dissolves at pH values above 5) [34,35]. When release in the large intestine is required, excipients sensitive to specific bacterial enzymes are used, as well as pH-sensitive polymers (pH 6.8 -7.5) [36,37].…”