They are used to deliver both systemically-acting and locally-acting medications.
The general principle is that the suppository is inserted as a solid, and will dissolve inside the body to deliver the medicine.
Rectal suppositories are commonly used for:
In 1991, Abd-El-Maeboud and his colleagues published a study in The Lancet, based upon their investigation into whether there was some hidden and forgotten knowledge behind the traditional shape of a rectal suppository.
Their research very clearly demonstrated that there was, indeed, a very good reason for the traditional "torpedo" shape; namely, that the shape had a strong influence on the extent to which the rectal suppository traveled internally — and, thus, upon its increased efficiency.
They (counter-intuitively) found that the ideal mode of insertion was to insert suppositories "blunt"-end first, rather than the generally used mode of inserting the "pointy"-end first. This conclusion was based on the greater distance of internal travel of the suppository once inserted, which was entirely a mechanical consequence of the natural actions of the bowel's muscular structure and the rectal configuration.
As a consequence, and in order to guarantee the maximum optimal efficiency, they recommended that all rectal suppositories be inserted "blunt"-end first. The findings of this single study have been challenged as insufficient evidence on which to base clinical practice.
Non-laxative rectal suppositories are to be used after defecation, so as not to be expelled before they are fully dissolved and the substance is absorbed. The use of a examination glove or a finger cot can ease insertion by protecting the rectal wall and the fingernail(s) from each other.
Alprostadil pellets are urethral suppositories used for the treatment of severe erectile dysfunction. They are marketed under the name Muse in the United States. Its use has diminished since the development of oral impotence medications, but is still on the market.
Some suppositories are made from a greasy base, such as cocoa butter, in which the active ingredient and other excipients are dissolved; this grease will melt at body temperature (this may be a source of discomfort for the patient, as the melted grease may pass through the anus during flatulences). Other suppositories are made from a water soluble base, such as polyethylene glycol. Suppositories made from polyethylene glycol are commonly used in vaginal and urethral suppositories. Glycerin suppositories are made of glycerol and gelatin.
Suppositories may also be used when a patient has a vomiting tendency, as oral medication can be vomited out.
The phrase "liquid suppository" is also sometimes applied to the activity of injecting a liquid, typically a laxative, with a small syringe, into the rectum.