Rectal/Vaginal Routes Flashcards Preview

Pharmaceutics > Rectal/Vaginal Routes > Flashcards

Flashcards in Rectal/Vaginal Routes Deck (23)
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1

When is rectal delivery used? (2)

for local action e.g. pain and itch

for systemic action

2

Features of the rectum: (2)

one cell layer thick epithelium

good blood circulation

3

Drug absorption is by...

Rate of absorption is ------ than the oral route?

passive diffusion

lower than than the oral due to small surface area

4

Following absorption, drug enters the...

haemorrhoidal veins

5

Advantages of rectal route (3)

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

6

Disadvantages of rectal route (3)

poor acceptability and compliance in certain countries

local slide effects

upward movement of the dosage form can increase first pass metabolism

7

Physiological factors that affect rectal absorption: (4)

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

8

Suppositories...

single dose

tapered at one end to aid insertion

diff shapes and sizes - smaller for children

9

Two types of suppository base:

Glyceride-type fatty bases
witepsol

– Water soluble bases
less commonly used

10

Problems with the hydrophilic bases: (2)

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

11

Excipients include..

melting point controlling agents e.g. beeswax

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

12

Vaginal wall is highly...

vascular with a relatively large surface area.

13

Physiological factors influence absorption in vagina:

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

as well as drug related factors

14

Advantages of vaginal administration (3)

local effects

systemic absorption high due to surface area

suitable where oral intake is restricted

15

Disadvantages of vaginal administration (3)

gender specific

acidic pH of vagina may enhance degradation of some drugs

menstruation cycle and hormonal variations affect systemic absorption

16

Ideal vaginal dosage form: (3)

colourless, odourless

free from local irritation

long acting, easy to apply

17

Semi-solid vaginal formulations

creams, ointments and gels

similar formulation to topical semi-solid formulations

18

Semi-solid vaginal formulations disadvantages: (3)

applicators tend to be messy and add to product cost

large scale production is challenging

no accurate dose

19

Vaginal suppositories (pessaries)

similar to the rectal ones

often use glycerol-gelatine as the base

20

Vaginal rings (implants)

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

controlled release of drug over a period of time

21

Vaginal tablets

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

22

Two major mechanisms:

- 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

23

Manufacture of rectal and vaginal suppositories

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.