Rectal route of administration

Through the rectal pathway it is possible to administer those drugs potentially capable of producing irritation of the gastric mucosa;

Administration routes

• enteral
  • Oral
  • Sublingual
  • Rectal
• parenteral
  • Intravenous
  • Intramuscular
  • subcutaneous
• INHALATION
• TRANSCUTANEOUS

in this way, in fact, the passage of the drug in the stomach is avoided. The rectal route of administration is also used in those patients who have had gastrointestinal interventions, in patients with protracted vomiting and in non-cooperating patients. However, the rectal route also has disadvantages which are:

• moderate absorption area;
• non-constant absorption, because depending on the point where it arrives the active ingredient can be absorbed at the level of the lower, medium or upper hemorrhoidal plexuses, with consequent passage or not at the level of the liver;
• possible expulsion of the pharmaceutical form.

Drug absorption by the rectum

1. Follows the general laws of the passage of drugs through the membranes
2. It is generally quantitatively inferior to that of oral drugs
3. It is very variable from drug to drug
4. It is very influenced by the filling state of the rectal ampulla
5. It is generally slow
6. Drugs given rectally can avoid (but only partially) the hepatic filter (the middle and lower hemorrhoidal veins are tributaries of the internal iliac), therefore the first-pass effect
7. Several drugs can cause irritation of the rectal mucosa.

The rectal route is an alternative to the oral route when the latter is not recommended for

1. Presence of vomiting
2. Unconscious patient
3. Degradability of the drug in digestive fluids or interference of food with absorption
4. Diseases that modify gastrointestinal absorption
5. Relevant first pass effect
6. Unpleasant taste