Rectal/Vaginal Routes

Question 1

When is rectal delivery used? (2)

Answer 1

for local action e.g. pain and itch

for systemic action

Question 2

Features of the rectum: (2)

Answer 2

one cell layer thick epithelium

good blood circulation

Question 3

Drug absorption is by…

Rate of absorption is —— than the oral route?

Answer 3

passive diffusion

lower than than the oral due to small surface area

Question 4

Following absorption, drug enters the…

Answer 4

haemorrhoidal veins

Question 5

Advantages of rectal route (3)

Answer 5

suitable for drugs liable to degrade in the GIT or first pass metabolism

suitable for elderly, terminally ill who are unable to swallow oral dosages

possible to remove dosage form to discontinue treatment

Question 6

Disadvantages of rectal route (3)

Answer 6

poor acceptability and compliance in certain countries

local slide effects

upward movement of the dosage form can increase first pass metabolism

Question 7

Physiological factors that affect rectal absorption: (4)

Answer 7

contents of the rectum
- presence of faeces affects drug dissolution in rectal fluids

motility of the rectal wall
- the activity of the muscles influences the rate of dissolution

quantity of rectal fluid
- limited fluid, makes dissolution the rate limiting step

properties of rectal mucus
- neutral pH leads to inability to control drug ionisation

Question 8

Suppositories…

Answer 8

single dose

tapered at one end to aid insertion

diff shapes and sizes - smaller for children

Question 9

Two types of suppository base:

Answer 9

Glyceride-type fatty bases
witepsol

– Water soluble bases
less commonly used

Question 10

Problems with the hydrophilic bases: (2)

Answer 10

small amount of liquid in rectum, it could draw water from rectal epithelium resulting in dehydration and irritation

many drugs are incompatible with hydrophilic bases

Question 11

Excipients include..

Answer 11

melting point controlling agents e.g. beeswax

surface active agents to enhance the wetting properties of the base with the rectal fluid

Question 12

Vaginal wall is highly…

Answer 12

vascular with a relatively large surface area.

Question 13

Physiological factors influence absorption in vagina:

Answer 13

thevolume, viscosity and pH of vaginal fluid, the stage of menstrual cycle, age, and sexual activity.

as well as drug related factors

Question 14

Advantages of vaginal administration (3)

Answer 14

local effects

systemic absorption high due to surface area

suitable where oral intake is restricted

Question 15

Disadvantages of vaginal administration (3)

Answer 15

gender specific

acidic pH of vagina may enhance degradation of some drugs

menstruation cycle and hormonal variations affect systemic absorption

Question 16

Ideal vaginal dosage form: (3)

Answer 16

colourless, odourless

free from local irritation

long acting, easy to apply

Question 17

Semi-solid vaginal formulations

Answer 17

creams, ointments and gels

similar formulation to topical semi-solid formulations

Question 18

Semi-solid vaginal formulations disadvantages: (3)

Answer 18

applicators tend to be messy and add to product cost

large scale production is challenging

no accurate dose

Question 19

Vaginal suppositories (pessaries)

Answer 19

similar to the rectal ones

often use glycerol-gelatine as the base

Question 20

Vaginal rings (implants)

Answer 20

rings are flexible, circular system containing the drug entrapped in a polymer network

controlled release of drug over a period of time

Question 21

Vaginal tablets

Answer 21

They are solid ,single-dose preparations ,similar to oral tablets in terms of formulation and manufacture

disintegrate in the small volume of vaginal fluid to allow drug release

Question 22

Two major mechanisms:

Answer 22

• melting
  designed to melt at body temp releasing the drug
• disintegration
  solid dosage forms release drugs by dissolution or disintegration, followed by dispersion of the contents in the vaginal fluids

Question 23

Manufacture of rectal and vaginal suppositories

Answer 23

using a moulding method.

• The base is heated to above the melting temperature, the drug dispersed or dissolved in the heated liquid.

•The molten product is poured into moulds, cooled then removed for final packing.
Or directly injected into the final packaging (mould strips) then sealed.