Rectal Suspension Enema

The active ingredient in the rectal suspension enema, a disposable (60 mL) unit, is mesalamine, also known as 5-aminosalicylic acid. Each rectal suspension enema unit contains 4 g of mesalamine. In addition to mesalamine, the preparation contains the inactive ingredients carbomer 934P, edetate disodium, potassium acetate, potassium met-... 

Each rectal suspension enema unit contains 4 g of mesalamine. In addition to mesalamine, the preparation contains the inactive ingredients carbomer 934P, edetate... 

Mesalamine (5-aminosalicylic acid asacol, others) is a salicylate that is used for its local effects in the treatment of inflammatory bowel disease (see Chapter 38). It currently is available as a suppository and rectal suspension enema (rowasa) for treatment of mild-to-moderate proctosigmoiditis Cl rectal suppository (canasa, others) for the treatment of distal ulcerative colitis, proctosigmoiditis, or proctitis. Oral formulations and controlled-release capsule that deliver drug to the lower intestine are efficacious in treatment of inflammatory bowel disease, in particular ulcerative colitis. Sulfasalazine (salicylazosulfapyridine azulfidine) contains mesalamine linked covalently to sulfapyridine (see Chapter 38) it is absorbed poorly after oral administration, but it is cleaved to its active components by bacteria in the colon. The drug is of benefit in the treatment of inflammatory bowel disease, principally because of the local actions of mesalamine. 

Suspension The usual dosage of mesalamine suspension enema in 60 mL units is 1 rectal instillation (4 g) once a day, preferably at bedtime, and retained for approximately 8 hours. While the effect may be seen within 3 to 21 days, the usual course of therapy is 3 to 6 weeks depending on symptoms and sigmoidoscopic findings. 

Rectal Mesalamine administered rectally as a suspension enema is poorly absorbed from the colon and is excreted principally in the feces during subsequent bowel movements. At steady state, approximately 10% to 30% of the daily 4 g dose can be recovered in cumulative 24-hour urine collections. 

Drugs are administrated by intravenous routes or ex-travascular routes including oral, sublingual, subcutaneous, intramuscular, rectal (by enema or suppository), and transdermal. Available dosage forms include suspensions, immediate-release capsules or tablets, sustained-release capsules or tablets, and enteric-coated capsules or tablets that resist dissolution in the acidic pfi of the stomach. 

An active substance administered as a suspension must dissolve before it can be absorbed. This may take considerable time which may be a problem due to the termination of rectal retention by defecation. For a systemic effect only a few, if any, suspension enemas are in use. For a local effect a suspension enema is frequently used, for example with mesalazine orbeclometasone. The choice between a suspension of the non-dissociated form of an active substance and a solution of the dissociated form can in the end only be based on biopharmaceutical research. 

Some suspensions have such a limited stability, that they have to be prepared just before use. An example is an enema with budesonide, where the active substance is incorporated in a dispersible tablet, that has to be added to a solution for rectal suspension. Here again, correct instruction of the user or caregiver is important. 

Rectal Avoids problems of stability in gastrointestinal tract No first-pass metabolism Useful if oral administration is not possible Unpopular Inconvenient Erratic absorption Irritation Suppositories, enemas (solutions, suspensions, emulsions), foams, ointments, creams... 

Enema are solution, suspension or emulsion (oil/water type) of medicament intended for rectal administration. 

Enemas These are available as solutions (aqueous or oily) as well as suspensions for rectal administration of drugs for cleaning, diagnostic, or therapeutic effect. Lotions These are available as solutions and suspensions to be applied topically without friction. They may either contain humectant, so that moisture is retained on the skin after application, or alcohol, which evaporates quickly imparting a cooling sensation to the skin. 

Solutions, suspensions, or retention enemas represent rectal dosage forms with very limited application. 

Glafenine suspension was administered and compared with glafenine suppositories and enemas. It is clear from Table (IX) that rectal administration of micro - enemas or suppositories containing this drug is not bioequivalent with oral dosage form (15). 

A water-insoluble active substance may be processed into an enema as a suspension. However, the dissolution rate may be insufficient for a systemic effect. If an active substance is too poorly soluble in water and thus in the rectal fluid, it cannot be absorbed at all. 

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