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45 Cards in this Set

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  • Back
creaming
reversible separation of a layer of emulsified particles
cracking or irreversible phase separation
never acceptable
phase inversion /emulsion type reversal
involves the reversion of an emulsion from o/w to w/o form or vice versa
extensive chemical degradation
cause substantial loss of active ing from dosage form
chemical degradation
produce toxic prdt
instability of drug prdt
dec bioavailabity => dec therapeutic effecacy
rate of rxn or degradation rate
velocity at w/c rxn occurs
rate of rxn depends upon
reactant conc
temp
pH
presence of solvents or additives
order of rxn
way in w/c the conc of drug or reactant in a chemical rxn affects the rate
zero order rxn
rate is independent of the conc of reactants
ist order rxn
-rate depends on the 1st power of the conc of a single reactant
-drug conc dec exponentially w/ time
half life
time required for the conc of drug to dec by 1/2
t 1/2
0.693/K1
factors that affect rxn rate
temperature
presence of solvent
chg in pH
presence of additives
inc temp
inc rxn rate
activation energy (ea)
amt of energy required to put the molecules in an activated state (to react)
water miscible solvents
PEG
low MW alcohols
stabilize the drug
H+ catalysis
predominates at dec pH
OH- catalysis
operates at inc pH
to determine effect of pH on degradation kinetics
measure decomposition at several H conc
ph of optimum stability
determined by plotting the log of the rate constant as fxn of ph
buffer salts
added to maintain formulation @ optimum pH

affect rate of degradation => salt in inc ionic stregth
inc salt conc

polyelectrolytes (citrate, phosphate)
substantially affect the magnitude of pka => chg rate constant

promote drug degradation thru gen acid or bases catalysis
surfactants
may accelerate or decelerate drug degradation
acceleration of degradation
caused by micellar catalysis
complexing agts
aromatic esters => inc half life in presence of caffeines

benzocaine
procaine
tetracaine
modes of pharmaceutical degradation
hydrolysis
oxidation
photolysis
most common degradation
hydrolysis
most common catalysts of hydrolytic degradation in soln
H+
OH-
esters
undergo hydrolytic rxn=> drug instability
oxidation
mediated thru rxn w/ atmospheric oxygen under ambient conditions (auto-oxidation)
medicinal compds
at room tem undergo - auto-oxidation

affected by oxygen dissolved insolvent

shld be pkgd in inert atmosphere (NTG) to exclude air fr containers
oxidation rxn
free radical mechanism chain rxn
antioxidants
react w/ free radicals by providing electrons and easily available H atoms -> prevent propagation of chain rxns
commonly used antioxidants
ascorbic acid
butylated hydroxyanisole (BHA)
butylated hydroxytoluene (BHT)
propyl gallate
sod bisulfite
sod sulfite
tocopherols
photolysis
degradation of drug molecules by normal sunlight or room light
undergo rxn
acquire suff energy
amber glass bottle ror opaque container
acts as barrier to this light thereby preventing or retarding photolysis
shelf life
calculated by rate of decomposition
water
most commonly used vehicle for drug soln
USP recognized types of water
purified
wat for inj
sterilize wat for inj
bacteriostatic wat for inj
sterile wat for inhalation
sterile wat for irrigation
oral drug soln
syrups
elixirs
galenicals formulation
aromatic water
tinctures
fluidextracts
spirits
sucrose conc
control of microbial growth