What is the bioavailability of suppositories

SuppositoriesDosage formsPreparations for rectal use Suppositories are single-dose medicinal preparations with a firm consistency that are intended for use in the rectum. The active ingredients are dissolved or dispersed in a matrix and are released when the suppository melts or comes into contact with liquid. On the one hand, suppositories are effective locally, for example as a laxative or for the treatment of hemorrhoids. On the other hand, the active ingredients contained can also be absorbed into the bloodstream and exert their effects in the body, bypassing the liver and first-pass metabolism. In contrast to tablets or capsules, suppositories can also be used for nausea, swallowing difficulties, poor general health and infants and small children.

synonymous: suppository, supp, suppos, suppositoria, rectal suppositories


Many medicines are available in the form of suppositories. Paracetamol suppositories are most often administered in practice to treat fever and pain in infants and children (photo, click to enlarge).


Suppositories are single-dose medicinal preparations with a firm consistency. They usually have an elongated, torpedo-like shape and a smooth surface. They are intended for use in the rectum. The mass is usually between 1 and 2 g.

The definition of suppositories sometimes also includes the rounder and usually somewhat heavier vaginal suppositories and the very rarely used urethral suppositories. However, the pharmacopoeia defines suppositories as rectal suppositories and differentiates them from vaginal suppositories.


The active pharmaceutical ingredients are distributed in a matrix that melts at body temperature or disperses or dissolves on contact with liquid. Hard fat (Adeps solidus), macrogols (PEG) and gelatin masses made from gelatine, glycerol and water are used as the base material. Cocoa butter is rarely used today, partly because the production is challenging due to the different crystal shapes. The active ingredients are dissolved or dispersed in the base.

Various auxiliaries such as dyes, preservatives, fillers, surface-active substances or lubricants can be added.

During production, the base mass with the active ingredients and auxiliaries is usually melted and poured into molds in which the mass solidifies. More rarely, suppositories are also pressed.


A basic distinction is made between a local and a systemic application.

In the local When applied, the active ingredients exert their effects in the rectum or at the anus. Typical examples are laxatives and hemorrhoidal suppositories. Salicylates such as mesalazine are given to treat inflammation of the rectal lining (proctitis).

At a systemic When used, the active ingredients contained are absorbed through the mucous membrane into the blood vessels and into the bloodstream and thus reach their place of action in the body.

The first-pass metabolism is partially bypassed because the blood from the lower hemorrhoidal veins, bypassing the liver, reaches the lower vena cava and thus into the bloodstream. There are various other advantages over oral administration:

  • Suppositories do not have to be swallowed and are ideal for infants, toddlers, children, for patients with swallowing difficulties and for those with nausea and vomiting.
  • Side effects in the digestive tract as well as nausea and vomiting can be avoided.
  • Administration is also possible in poor general condition or unconsciousness.
  • In contrast to an injection, administration is not painful.

Attention: The maximum plasma concentration (Cmax) for suppositories is often reached later than for oral administration. So if a quick onset of action is desired - for example in the case of a migraine - other drug forms may be preferable. This also applies, for example, to paracetamol suppositories, in which, according to the specialist information, the Cmax is only reached after about 1.5 to 2 hours. Often the bioavailability of suppositories is also lower.


According to the specialist information and the package insert.

  • The bowel should be empty because the administration of the suppository can trigger the defecation reflex. Of course, this does not apply to the use of laxatives.
  • Wash hands with soap and water or put on gloves or a finger cot.
  • Carefully remove the suppository from the packaging.
  • In the supine position and with your legs drawn up, insert the uvula deep into the rectum behind the sphincter. If a local effect is desired, e.g. against hemorrhoids, do not insert too far (still palpable).
  • To make application easier, fatty suppositories can be warmed up slightly and PEG suppositories can be moistened with warm water.
  • Wash hands with soap and water.
Pointed or Blunt End First?

Suppositories are usually inserted into the rectum with the pointed end forward. The manufacturers usually also provide for this. Since the publication by Abd-el-Maeboud et al. (1991) however, it is also recommended to use suppositories with the blunt To be administered at the end forwards because it should make it harder to slide out. However, this idea is controversial (Bradshaw & Price, 2007).

Can suppositories be divided?

The manufacturers do not provide for the sharing of suppositories. Suppositories do not contain any break lines and dividing is hardly mentioned in the technical information. In addition, the active ingredient can theoretically be distributed unevenly in a suppository. The suppositories can break, become contaminated and the dividing is laborious.

For the reasons mentioned, suppositories should only be divided in exceptional cases. This should be done under hygienic conditions and lengthways, as in this way two identical parts are created.


Suppositories should usually be stored at room temperature between 15 and 25 ° C. They are kept out of the reach of children. Suppositories can begin to melt at high temperatures. This is especially important in summer and on vacation. When putting together a first-aid kit, suppositories should be avoided if possible.

unwanted effects

The specific possible undesirable effects of suppositories include local irritation, pain and triggering of the defecation reflex. The administration in the genital area is uncomfortable and embarrassing for some patients. It is more complicated compared to tablets or capsules.

Accidental ingestion of suppositories

Suppositories are intended for rectal use in the rectum and should not be ingested.

What happens if a suppository is accidentally swallowed instead of inserted?

The basic masses used, such as hard fat, macrogols or gelatine, are unproblematic for the body. They are either digested in the intestine and their components are absorbed. Or they are excreted unchanged in the stool.

Suppositories are designed to melt inside the body and release their active ingredients. The release also takes place in the case of oral use and the active ingredients can be absorbed. However, the pharmacokinetics differ, for example due to the first-pass metabolism with oral administration.

Furthermore, some active ingredients, such as local anesthetics, are intended exclusively for local use. Side effects are possible. For example, the salicylates can irritate the gastric mucosa.

The consequences of ingestion depend on the active ingredients, the dose and the patient and must be assessed individually. Patients should contact a specialist immediately.

see also

Vaginal suppositories

  • Abd-el-Maeboud K.H. et al. Rectal suppository: commonsense and mode of insertion. Lancet, 1991, 338 (8770), 798-800 Pubmed
  • Medicinal product information (CH)
  • Bradshaw A., Price L. Rectal suppository insertion: the reliability of the evidence as a basis for nursing practice. J Clin Nurs, 2007, 16 (1), 98-103 Pubmed
  • European Pharmacopoeia PhEur
  • Pharmaceutical technology textbooks and manuals
  • Oesch P. On the manufacture and testing of suppositories. Doctoral thesis, Zurich, 1944
  • swell

Conflicts of Interest: None / Independent. The author has no relationships with the manufacturers and is not involved in the sale of the products mentioned.

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This article was last changed on 6.2.2021.
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