3.3) Factors that affect medicine Flashcards
(36 cards)
Define stability of a medicine
*a medicine’s capacity to remain within the specifications established to ensure its identity, strength and purity.
-the ability of the medicine to resist deterioration
how is the stability of a medicine expressed
in terms of shelf-life
A product’s shelf-life is indicated by
expiry date on the product
define expiry date
means that the specific product cannot be used after this date because the conc. of API decreases and becomes lower than the therapeutic conc.
*in some cases they become toxic and harmful to patients when it degrades
What happens after opening a medicine
the expiry date will be shorter as a result of decr. conc. of medicine during usage and effects of environmental factors
how long can eye drops last
for one month after opening dropper
How long can syrups and suspension of antibiotics last
for 1 week if stored at room temp
for 2 weeks if stored at 4*C
How long can tablets and capsules last
remain stable in package
*after removal, expiry date will change
How long can ampoules last
must be used immediately
*vials (multi dose) are stable for 24h due to preservatives
Name the environmental factors that affect stability
- moisture
- oxygen
- light (photolysis)
- Temperature
5.pH
What happens to water-soluble medicines in solid dosage form
they will dissolve in any moisture layer on the solid surface
*the API is then in an aqueous environment
Effect of moisture on stability
-enhances hydrolytic degradation (splitting of molecule)
-water catalyzes chemical rxns such as oxidation, hydrolysis and reduction rxn
-water promotes microbial growth
-packaging materials such as Glass and Plastic are usually used to prevent medicine exposure to high humid conditions
How can a medicine’s susceptibility to oxygen presence be tested
by comparing its stability in ampoules purged with oxygen to that when stored under nitrogen
How can medicine that has a higher rate of decomposition when exposed to oxygen be stabilised
- by replacing oxygen in storage container with nitrogen or CO2
- by keeping them out of contact with heavy metals
- with antioxidants
Effect of O2 on medicine stability
-it enhances the hydrolytic degradation
-exposure of medicine formulations to O2 affects their stability
How does light affect medicine stability
thru its energy or thermal effect leading to oxidation (decomposition by light)
Relation ship between wavelength and energy absorbed
The shorter the wavelength, the more energy is absorbed per mole
Name the sources of light
-sunlight
-metal halide lamps’-fluorescent lamps
-other indoor light sources
Photolysis is prevented by
-suitable packing in amber-coloured bottles
-cardboard outer packages
-aluminum foil wrapper
How can medicines susceptibility to light be tested
comparing its stability when exposed to light to that when stored in the dark
Where should Photo labile medicines be stored
in containers of amber glass
-should be kept in the dark as a precaution
Energy absorbed thru UV light
50-400 wavelength
=287-72 kcal per mole
Energy absorbed thru visible light
400-750 wavelength
= 287-72/36-1 kcal per mole
Energy absorbed thru I.r.
750-10000 wavelength
= 36-1 kcal per mole
