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Rectal administration

Definition

These preparations are administered via the rectum, which may exert a local effect on the GI mucosa (e.g. an anti‐inflammatory effect in ulcerative colitis) or have systemic effects (e.g. analgesics or to relieve vomiting) (Potter and Perry [289]).

Related theory

Suppositories

Suppositories are solid preparations that may contain one or more drugs. The drugs are normally ground or sieved and then dissolved or dispersed into a glyceride‐type fatty acid or water‐soluble base. These suppositories will either melt after insertion into the body or dissolve and mix with the available volume of rectal fluid (Aulton and Taylor [16]).

Enemas

Enemas are solutions or dispersions of a drug in a small volume of water or oil. These preparations are presented in a small plastic container in the shape of a bulb, which contains the drug and an application tube. The bulb can be compressed when the tube has been inserted in the rectum to deliver the drug. Retention enemas are often in larger volumes, up to 100 mL, while some rectal preparations come in the form of foams. Enemas can be difficult for patients to use by themselves compared to suppositories and therefore their use is not as widespread (Aulton and Taylor [16]).

Evidence‐based approaches

The advantages of rectal administration include the following (Chernecky et al. [39], Perry [281]):

The drug can be administered when the patient cannot use the oral route, for example if the patient is vomiting or is post‐operative and therefore either unconscious or unable to ingest anything via the oral route.
In some categories of patient (e.g. children and the elderly), it may be easier to use the rectal route than the oral one as it does not require swallowing.
The drug may be less suited to the oral route; for example, the oral route can cause severe local GI side‐effects.
The drug may not be stable after GI administration or it may have an unacceptable taste that makes it unpalatable via the oral route.
Rectal administration rarely causes local irritation or side‐effects.

The disadvantages of the rectal route include the following (Chernecky et al. [39], Downie et al. [82], Perry [281]):

Some patients have strong feelings against the rectal route, and some have feelings of discomfort and embarrassment.
There can be slow and incomplete absorption.
The development of proctitis has been reported with rectal drug administration.
It is contraindicated in patients who have had rectal surgery or have active rectal bleeding.

After a suppository has been inserted into the rectum, body temperature melts the suppository so the medication can be distributed. Proper placement is important to promote retention of the medication until it dissolves and is absorbed into the mucosa (Perry [281]).

For further information about the administration of rectal medication, see Procedure guideline 6.22: Suppository administration.