Rectal Drug Delivery Flashcards
What are some reasons why rectal drug delivery is used instead of other forms of drug delivery?
- Problems with GI tract
- Unconscious, nauseous or postoperative patients
- Very young or old patients
- Mentally disturbed patients
- Unacceptable taste
- Cannot withstand the pH of the stomach
- Pain or itching mostly due to occurrence of haemorrhoids
- Local anaesthetics and anti-inflammatory compounds
What is the rectum?
Makes up the last part of the colon on the GI tract
How is the drug absorbed in the rectum?
- Drug molecules enter through the lower end of the rectum into the highly metabolising liver via the portal vein
- The drug bioavailability may be less than 100% as the drug molecules can enter the general circulation intact
What are the physiological factors that effect the absorption of the drug from the rectum?
- There is only 3ml of mucus which means that it’s difficult for drugs which aren’t too water soluble to dissolve and be absorbed
- pH is 7.5 with little buffer capacity so something acidic or alkaline would be painful
- No peptidase or esterase activity present in the rectum (much greater stability of peptide like drugs)
- Motility of the rectal wall: contractions
Explain the process that occurs when the suppository enters the rectum?
- Melting or dissolution of base
- Release and diffusion of drug
- Absorption into the rectal mucosa
What are the dosage forms for rectal administration?
- Suppositories
- Tablets
- Capsules
- Ointments
- Enemas
What is a suppository?
Drug rectal delivery system that’s in the shape of a torpedo which dissolves or melts into your blood stream
What are the main requirements for a suppository?
- Melt at or below body temperature or dissolve in body fluids
- Easily moulded and removed from mould
- Chemically stable even when molten
- Release the active ingredient easily
- Easy to handle
- Non toxic and non irritant
What were the suppositories typically made of in the past?
Fatty bases
What are the main hydrophilic bases used in the formation of suppository?
- Glycerol: gelatin bases (main suppository component)
2. Macrogols (derivatives of polyethylene glycols
mainly used for laxative suppositories)
What is the mechanism of formation of a suppository?
- Solution
- Gel
- Solution
What are the problem with hydrophilic bases?
- Small amount of water in the rectum
- Base can react with the water and cause pain due to dehydration as water is drawn from the epithelium (painful sensation)
- Glycerinated gelatin base for the Glycerol should therefore be dipped in water prior to the insertion into the rectum
- Many drugs (phenols, sulphonamides) are incompatible with hydrophilic bases
- Drug release could be slow due to interaction with the base
What are the other ingredients that are present in the suppositories?
- Stiffening agents
- Suspending agents
- Emulsifying agents
- Preservatives
What are some examples of suppositories that are available on the market?
- Alvedon suppositories: relieve pain in children who find it hard to swallow tablets
- Duclolax: relieves constipation and helps restore regularity
- Anusol: internal relief of haemorrhoids (piles)
- Shrink piles
- Soothes itching
- Relieves pain and discomfort
- effective soothing relief
What is an enema? And what are they frequently used for?
- Fluid injected into the lower bowel by way of the rectum
- Relieve constipation or cleaning of bowel before analysing
- Topical administration of medication into rectum like corticosteroids for treatment of inflammatory bowel disease
- Barium contrast is used as an enema to radiography to visualise the bowel
