Rectal mucosa

Cascara sagrada is used as a cathartic. It is most useful when prepared as a fluid extract, and tends to be a mild laxative causing Htfle discomfort. However, on prolonged use it may result in characteristic melanotic pigmentation of the rectal mucosa. The bitter taste can be lessened, owing to neutralization of the acid constituents, if the ground substance is moistened and mixed with magnesium or calcium hydroxide. This treatment may lessen the potency of the preparation. 

Hawkey, C.J. and Truelove, S.C. (1983). Inhibition of prostaglandin synthetase in human rectal mucosa. Gut 24, 213-217. 

Human immunodeficiency virus proteins were detected by immunohisto-chemistry in the duodenal and rectal mucosa (Jl). HIV infected cells were... 

In view of the high level of infection amongst male homosexuals, it is of interest that lymphoid follicles, equivalent to Peyer s patches are abundant in the human rectal mucosa. 

Rectal administration-, burning of rectal mucosa, mild proctitis... 

Both interferon-a and - 3 have been shown to be absorbed across the rectal mucosa when given with the fatty acid linolenic acid as mixed micelles. In the absence of a permeation enhancer, rectally administered interferons (165 aa) do not achieve detectable levels in blood nor lymph. With 0.56% linolenic acid, a significant degree of lymphatic absorption of interferon-a and -P was detected [20]. The rectally absorbed interferon first distributes into the lymphatics, and interferon concentration is much higher in lymph than... 

The use of water-soluble bases may result in some irritation because, as they take up water and dissolve, they may produce slight dehydration of the rectal mucosa. They are widely used, however, and release the drug by dissolving and mixing with the aqueous body fluids. PEG suppository bases and glycerinated gelatin are the most popular in this class. 

In the past two decades, many studies have tested adjuvants that act by either permeabilizing the rectal mucosa or inhibiting drug degradation. Oral and rectal routes of drug administration are unsuitable for adequate absorption of various compounds with a peptide or protein structure and of several hydrophilic antibiotics. The use of absorption enhancers, e.g., salicylates, enamines, surfactants, and straight-chain fatty acids, has gained wide interest... 

An important issue that has been recognized recently concerns the potential adverse effect of absorption enhancers on the rectal mucosa, as shown in rats after a single application [61,62], Safety evaluation of the applicability of absorption enhancers is imperative. In clinical application, medium-chain fatty acids such as sodium caprate are used only for suppositories containing antibiotics [36],... 

Van Hoogdalem, E.J., et al. 1990. Topical effects of absorption enhancing agents on the rectal mucosa of rats in vivo. J Pharm Sci 79 866. 

In this chapter, we especially focus on the strategies for enhancement of rectal absorption of various drugs including peptides and proteins from rectal mucosa using pharmaceutically useful excipients, cyclodextrins (CyDs), and the other absorption enhancers. 

FIGURE 8.6 Permeation profiles of morphine (a) and a-CyD (b) through rabbit rectal mucosa after applications of morphine hydrochloride and a-CyD in Ringer s solution (pH 7.4) at 37°C. Each point represents the mean SE of four experiments. p < 0.05, compared with MH alone. 

Nakanishi, K., et al. 1984. Effect of nonsteroidal anti-inflammatory drugs on the permeability of the rectal mucosa. Chem Pharm Bull 32 1956. 

In tests designed to evaluate the primary irritation of mucous membranes, the tissues of choice (wherever possible) should be the specific mucosal to which the chemical is applied. Differences in histology, absorptive capacity, and pH ranges of the mouth, eye, genitourinary, and rectal mucosa are great enough that results obtained on one mucosa may not apply for the other. 

Although intravenous diazepam is the preferred route, the undiluted intravenous solution of diazepam can be given rectally, and is effective in the emergency management of seizures in children (29). Rectal gel is an alternative, and can be given by non-medical personnel (30). Adverse effects of rectal diazepam are rare and mild. Animal studies and clinical experience have not shown damage to the rectal mucosa. 

The rectal mucosa has a rich blood and lymph supply and, in general, dose requirements are either the same or slightly greater than those needed for oral use. Drugs chiefly enter the portal system, but those that are subject to hepatic first-pass elimination may escape this if they are absorbed from the lower rectum which drains directly to the systemic circulation. The degree of presystemic elimination thus depends on distribution within the rectum and this is somewhat unpredictable. 

Sodium salicylate and 5-methoxysalicylate increased the absorption of insulin. Sodium glycocholate was more effective than sodium taurocholate but less effective than sodium-deoxycholate and PE-9-laurylether in enhancing rectal insulin absorption in rabbits. The role of disodium EDTA in the enhancement of rectal drug absorption, along with the damaging effects on the rectal mucosa, has been described for several drugs. ... 

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