Vaginal Delivery Flashcards
what are the main anatomical features of the vagina? and what’s the importance?
- 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
what are the main features of the vaginal fluid?
- aqueous
- pH 3.5 to 5
how can the volume and composition of the vaginal fluid change?
The pH, fibrosity and mucin content increase with age
The viscosity, cellularity and albumin content decrease with age
what’s the advantages and disadvantages of vaginal route?
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
what is drug absorption mediated by in the vagina?
Transcellular route
Intracellular route
Receptor mediated transport mechanisms
why is it good that the vagina has a multiple routes for drug absorption?
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
what are physiological factors that affect drug absorption?
Thickness of the vaginal epithelium
pH
Volume and composition of vaginal fluid
how does the vaginal fluid volume and composition affect drug absorption?
- larger volume increases the absorption rate for poorly water soluble drugs
- pH of the vagina will affect the release of pH sensitive drugs
what are physiochemical factors that affect drug absorption?
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
what don’t you want to do if you would like your intended drug to target the vagina locally?
Dont want drug to be too absorbed into blood vessels
explain gels as a system
A gel is a semi-solid system consisting of a continuous solid network dispersed within a liquid medium.
what characteristics of vaginal gels are important?
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
what are disadvantages to vaginal gels?
messy to apply
leak from the vagina
may not absorb/administer an exact amount of drug
poor pt compliance
explain what creams are as a dosage form?
semi solid emulsion of oil-in-water or water-in-oil
what are the advantages of vaginal tablets?
easy to manufacture
relatively cheap to make
easy to place within the vagina
release rate can be varied by the use of excipients
how can you increase the retention time of a vaginal tablet?
by the use of:
* mucoadhesive polymers and non soluble polymers (Carbomers, HPMC and Chitosan)
what materials decrease absorption from vaginal tablets?
hydrophobic material-Ethylcellulose
Insoluble material- Colloidal silicon dioxide
Enteric coating-HPMCP
(Looks like it’s mainly acidic polymers)
what material enhance absorption in vaginal tablets?
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
explain what vaginal pessaries are?
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
explain what vaginal rings are?
torus shaped
1 or more drugs delivered in a sustained fashion
Inserted up to twelve months
local or systemic effect
why are vaginal rings used?
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
what are vaginal rings composed of?
silicone elastomers or EVAc
what are the two types of vaginal rings?
- matrix ring
- reservoir ring
what is a matrix vaginal ring?
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
