Vaginal Delivery Flashcards

1
Q

what are the main anatomical features of the vagina? and what’s the importance?

A
  • collapsible musculomembranous tube
    - drugs will interact with the membrane
  • highly folded into rugae
    - large SA
    - rapid drug absorption
  • blood supply by the internal iliac and uterine artery
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1
Q

what are the main features of the vaginal fluid?

A
  • aqueous
  • pH 3.5 to 5
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2
Q

how can the volume and composition of the vaginal fluid change?

A

The pH, fibrosity and mucin content increase with age
The viscosity, cellularity and albumin content decrease with age

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3
Q

what’s the advantages and disadvantages of vaginal route?

A

ADV’s
- local admin
- rich blood supply
- avoid hepatic FPM
- uterine targeting
- reduced GI side effects
- self insertion & removal

DISADV’s
- gender specific
- less convenient
- permeability vary
- ageing
- local irritaton

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4
Q

what is drug absorption mediated by in the vagina?

A

Transcellular route
Intracellular route
Receptor mediated transport mechanisms

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5
Q

why is it good that the vagina has a multiple routes for drug absorption?

A

if there the drug absorption was limited to one route and the route becomes saturated with drug molecules, causing the rate of absorption to slow down

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6
Q

what are physiological factors that affect drug absorption?

A

Thickness of the vaginal epithelium
pH
Volume and composition of vaginal fluid

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7
Q

how does the vaginal fluid volume and composition affect drug absorption?

A
  • larger volume increases the absorption rate for poorly water soluble drugs
  • pH of the vagina will affect the release of pH sensitive drugs
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8
Q

what are physiochemical factors that affect drug absorption?

A

molecular weight - smaller molecules are easier to cross mucosal membrane
lipophilicity (log P) - More lipophilic drugs can pass through cell membranes more easily.
ionisation - Drugs in their non-ionized form are generally better absorbed
chemicals
solubility-Drugs that are more soluble in vaginal fluids will be more readily absorbed

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9
Q

what don’t you want to do if you would like your intended drug to target the vagina locally?

A

Dont want drug to be too absorbed into blood vessels

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10
Q

explain gels as a system

A

A gel is a semi-solid system consisting of a continuous solid network dispersed within a liquid medium.

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11
Q

what characteristics of vaginal gels are important?

A

the vaginal gel may swell and spread over the vaginal wall, this allows a localised drug delivery and sustain release over a longer period of time

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12
Q

what are disadvantages to vaginal gels?

A

messy to apply
leak from the vagina
may not absorb/administer an exact amount of drug
poor pt compliance

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13
Q

explain what creams are as a dosage form?

A

semi solid emulsion of oil-in-water or water-in-oil

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14
Q

what are the advantages of vaginal tablets?

A

easy to manufacture
relatively cheap to make
easy to place within the vagina
release rate can be varied by the use of excipients

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15
Q

how can you increase the retention time of a vaginal tablet?

A

by the use of:
* mucoadhesive polymers and non soluble polymers (Carbomers, HPMC and Chitosan)

16
Q

what materials decrease absorption from vaginal tablets?

A

hydrophobic material-Ethylcellulose
Insoluble material- Colloidal silicon dioxide
Enteric coating-HPMCP

(Looks like it’s mainly acidic polymers)

17
Q

what material enhance absorption in vaginal tablets?

A

surfactants - These can improve the solubility of the drug and enhance its absorption by altering the properties of the mucosal barrier

bile salts - Increase the permeability of the vaginal mucosa by interacting with lipid bilayers and altering membrane fluidity

18
Q

explain what vaginal pessaries are?

A

solid single dose preperations
shape varies - mainly ovoid
1 or more API dispersed/dissolved in a suitable base

the suitable base may be soluble or dispersible in water or melt at body temperature

19
Q

explain what vaginal rings are?

A

torus shaped
1 or more drugs delivered in a sustained fashion
Inserted up to twelve months
local or systemic effect

20
Q

why are vaginal rings used?

A

Overcome many of the disadvantages associated with more traditional vaginal drug dosage forms

Major advantage is providing long-term, continuous release of drug(s) at constant pre- determined rates, thereby increasing cost- effectiveness, patient compliance and therapeutic efficacy

21
Q

what are vaginal rings composed of?

A

silicone elastomers or EVAc

22
Q

what are the two types of vaginal rings?

A
  • matrix ring
  • reservoir ring
23
Q

what is a matrix vaginal ring?

A

drug homogeneously dispersed through a ring, release rate proportional to drug loading and SA of the ring

made in a single step

in a silicone elastomer

24
Q

what’s the typical release profile of matrix VR’s?

A
25
Q

what’s the typical release profile of reservoir VR’s?

A
26
Q

what is a reservoir VR as a dosage form?

A

API dispersed in a centralised core, encapsulated by a drug free layer of polymer

27
Q

how can you modify the rate of drug release in reservoir VR?

A

changing the core diameter or thickness of the nonmedicated coating

28
Q

what factors influencing drug release/ PK/absorption between fluid and ring?

A
  • ring type
  • drug loading
  • polymer type
  • polymer solubility
  • polymer diffusion
  • fluid volume
  • fluid solubility
  • fluid diffusion
29
Q

what factors influencing drug release/ PK/absorption between the epithelium and ring?

A
  • ring type
  • polymer solubility
  • polymer diffusion
  • drug loading
  • epithelial thickness
  • crystal lattice E
30
Q

what are the two types of diffusion from the vaginal ring?

A

direct mechanism: ring to the tissue

indirect mechanism: ring to the fluid to the tissue

31
Q

why are the following log P’s not ideal for drug absorption from vaginal rings…

5.78
-1.2

A

5.78 - too hydrophobic

-1.2 - too soluble within water that it won’t be soluble within the polymer