Rectal Drug delivery

Question 1

Why use rectal administration

Answer 1

• oral administration problematic e.g NMB, unconscious, elderly, child, nausea
• Drug not appt for GIT administration e.g GI side effects, unstable at pH values, taste
• Local administration of drugs e.g proctisit (UC) - administration of local anti inflammatories, haemorrhoids pain

Question 2

What physiological factors of the rectum affect drug absorption?

Answer 2

1. Quantity of fluid only 3ml - dissolution of only slightly water soluble drugs is slow and hydrophilic bases draw water out from epithelium causing irritation
2. Mucus pH around 7.5 - little buffering capacity so if drug is acid or base - leads to irritation
3. Gastric motility - contraction waves, pressure from organs

Question 3

What are requirements of bases?

Answer 3

melt at or below body temp
solidify on cooling
Chemical stability
Non irritating, non toxic

Question 4

two types of bases and their mechanisms of solidification?

Answer 4

Fatty e.g theombroma oil, Witepsol - Melting, crystallisation, melting

Hydrophilic e.g glycerine, macrogol - Solution, Gel, solution

Question 5

Why are hydrophilic bases problematic?

Answer 5

• 3ml lack of fluid in rectum, they require water to dissolve so draw water from epithelium causing dehydration & irritation
• Prepared with glycerinated gelatin base so should be dipped in water before insertion (as form gel on cooling)?
• Gelatin biopolymers contains reactive functional groups, react with other drugs, may slow down drug release

Question 6

give example of a pharmaceutical suppository

Answer 6

Dulcolax laxative for constipation

Question 7

Other suppository ingredients?

Answer 7

API, base
stiffening agents - mechanical strength
emulsifying agents
preservatives

Question 8

How to make a suppository?

Answer 8

Melt base
Incorporate powder - stir into base
Pour into supp moulds evenly to avoid trapped bubbles
Cool and harden

Question 9

What are enemas/types

Answer 9

Fluid injected into lower bowel by recutm
Cleansing e.g relieve constipation, before procedure
Topical administration e.g corticosteroids/mesalazine
Contrast agents e.g Barium