Flashcards in Rectal Drug Delivery Deck (15):
What are some reasons why rectal drug delivery is used instead of other forms of drug delivery?
1. Problems with GI tract
2. Unconscious, nauseous or postoperative patients
3. Very young or old patients
4. Mentally disturbed patients
5. Unacceptable taste
6. Cannot withstand the pH of the stomach
7. Pain or itching mostly due to occurrence of haemorrhoids
8. 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?
1. Drug molecules enter through the lower end of the rectum into the highly metabolising liver via the portal vein
2. 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?
1. 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
2. pH is 7.5 with little buffer capacity so something acidic or alkaline would be painful
3. No peptidase or esterase activity present in the rectum (much greater stability of peptide like drugs)
4. Motility of the rectal wall: contractions
Explain the process that occurs when the suppository enters the rectum?
1. Melting or dissolution of base
2. Release and diffusion of drug
3. Absorption into the rectal mucosa
What are the dosage forms for rectal administration?
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?
1. Melt at or below body temperature or dissolve in body fluids
2. Easily moulded and removed from mould
3. Chemically stable even when molten
4. Release the active ingredient easily
5. Easy to handle
6. Non toxic and non irritant
What were the suppositories typically made of in the past?
What are the main hydrophilic bases used in the formation of suppository?
1. 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?
What are the problem with hydrophilic bases?
1. Small amount of water in the rectum
2. Base can react with the water and cause pain due to dehydration as water is drawn from the epithelium (painful sensation)
3. Glycerinated gelatin base for the Glycerol should therefore be dipped in water prior to the insertion into the rectum
4. Many drugs (phenols, sulphonamides) are incompatible with hydrophilic bases
5. Drug release could be slow due to interaction with the base
What are the other ingredients that are present in the suppositories?
1. Stiffening agents
2. Suspending agents
3. Emulsifying agents
What are some examples of suppositories that are available on the market?
1. Alvedon suppositories: relieve pain in children who find it hard to swallow tablets
2. Duclolax: relieves constipation and helps restore regularity
3. Anusol: internal relief of haemorrhoids (piles)
- Shrink piles
- Soothes itching
- Relieves pain and discomfort
- effective soothing relief