Part 1 Flashcards
if a drug bottle has the expiration:
3/1/24
when can you use it until
the last day of march (3/31)
name 3 drug stability issues and 3 mechanisms of degradation
stability issues:
-loss of Active ingredient from dosage form
-a toxic product can be produced with undesirable effects
-decreased bioavailability
3 mechanisms of degradation:
oxidation, hydrolysis, photolysis
the mechanisms of degradation in regards to drug stability are _____ factors
environmental –
oxidation (atmospheric oxygen)
photolysis (by sunlight OR room light)
hydrolysis
what is the most frequent type/mechanism of degradation of drugs?
hydrolysis
name a drug that has a big issue with hydrolysis and what this means for the dosage forms which it is available
aspirin is very prone to hydrolysis
therefore, when it’s formulated as a suppository, water is not included
name 3 medicinal compounds that are very susceptible to hydrolysis
esters
lactams
amides
the OXIDATION mechanism of degradation is usually mediated through reaction with ____ under _____ conditions
reaction with molecular oxygen under ambient conditions (AUTO-OXIDATION)
what is added to drugs to prevent oxidation
antioxidants
true or false
photolysis is the degradation of drug molecules by normal sunlight
FALSE
normal sunlight OR room light
give a method of shelf life estimation
Q10 method
give the definition of stability
the extent to which a product retains, within specified limits and throughout its period of storage and use, the SAME PROPERTIES AND CHARACTERISTICS THAT IT POSSESSED AT THE TIME OF ITS MANUFACTURE
name the 5 types of stability
chemical
physical
microbiological
therapeutic
toxicologic
odor is an example of what kind of stability?
physical
name 3 factors that must be considered because they can affect the chemical stability of the product
storage conditions
the dispensing container
anticipating interactions that may occur
explain how storage conditions can affect chemical stability
temperature
light
humidity
(environmental factors)
explain how different containers can affect chemical stability
glass vs plastic: plastic is preferred because it wont break but sometimes it has chemical stability issues with the product
clear vs amber – amber protects against photolysis if sensitive to light
explain why it is important to anticipate interactions when trying to preserve chemical stability
anticipate the interactions that can occur when mixing drugs or when selecting certain DOSAGE FORMS
IE: ASPIRIN SUPPOSITORY DOES NOT HAVE WATER
give an example of therapeutic instability
the insulin is there but has no therapeutic effect when injected
define kinetics
motion or movement
rate of change over time
give the rate equation and explain the variables
dC/dt -(C) ^n
dC = change in concentration
dt= change in time
dC/dt = change of concentration with change in time (rate of reaction)
C = concentration
n= the ORDER of the reaction
it’s a minus sign because the concentration is decreasing over time when considering stability
what is zero order kinetics
the rate of the reaction is INDEPENDENT of the concentration of the reactants
give the formula for the rate constant and the slope in a graph of a zero order reaction
ko = -dC/dt
slope = -ko
give the full formula for ko in a zero order reaction
Ko = (C1-C2)/(t2-t1)
what does Ct mean in zero order reaction
concentration at “t” time
give the formula for Ct in a zero order reaction
Ct = C0-K0t
what is the formula and units for Ko?
KO = (C1-C2)/(T2-T1)
units = concentration/time
give the formula for t1/2 of a zero order reaction
t1/2 = C0/2K0
true or false
every drug has a constant Ko. the value only changes for different drugs
TRUE
the higher the Co value, the ____ the half life
higher (longer)
true or false
in zero order kinetics, the t1/2 does not depend on concentration
FALSE
it does.
formula is
t1/2 = Co/2ko
higher the concentration, higher the half life
true or false
the rate constant for a zero order reaction can be negative
FALSE – IT CANT
must be positive. we can’t have a negative drug value in the body
in ZERO ORDER kinetics, the graph is ____ vs _____. what is on the y axis? what is on the x axis?
y axis = concentration
x axis = time
in first order kinetics, the rate depends on…..
the first power of the concentration of a single reactant
in first order kinetics, what happens to concentration with time?
concentration decreases exponentially with time
what is the rate constant for 1st order kinetics?
what is the rate constant for zero order kinetics?
rate constant for 1st order kinetics = k(c)
for 0 order = Ko
first order kinetics:
__________ = kc
-dc/dt
what is the slope formula for 1st order kinetics
-k/2.303
true or false
for 1st order kinetics, K will be constant for the same drug but different for every drug (like Ko for zero order)
TRUE
Give the formula to calculating the rate constant in first order kinetics
K = (ln C1 - ln C2) / (t2-t1)
give the formula to calculate Ct for 1st order kinetics
ln Ct = ln Co - Kt
most drugs follow ______ order elimination rate constant
1ST
second is ZERO order
give the formula to calculate half life in first order kinetics
t1/2 = 0.693/k
true or false
for zero order kinetics, the half life does not depend on concentration but for first order it does
FALSE
half life depends on concentration for zero order (t1/2 = Co/2Kt)
half life does NOT depend on concentration for first order (t1/2 = 0.693/k)
ln ____ = 0.693
ln2
what are the units of the rate constant for zero order?
what about first order?
zero order:
Ko units = concentration/time
first order:
K units = 1/time (NOT CONC DEPENDENT)
for first order kinetics, dc/dt depends on……
drug concentration
define shelf life
the time required for 10% of drug to degrade
(WITH 90% OF INTACT DRUG REMAINING)
Give the arrhenius equation.
what is it used to calculate?
used in finding the energy of activation
log K2/K1 = Ea (T2-T1) / 2.3 * R*T1 *T2
K = reaction rate constant
T = absolute temp
R = gas constant
Ea= energy of activation
When using the arrhenius equation, Ea was calculated to be 25,651kcal/mol
what does this mean?
if energy is not higher than 25,651 kcal/mol, degradation DOES NOT TAKE PLACE
in the arrhenius equation, what is the value of the gas constant (R)?
1.987 cal K ^-1 mol ^-1
what is the method of estimating shelf life
Q10 method
true or false
for a 1st order reaction, as the concentration increases the shelf life also increases
FALSE – the shelf life remains the same regardless of concentration
RATE of degradation is dependent on concentration but not the shelf life
true or false
for a zero order reaction, the shelf life IS dependent on concentration but not the rate of the reaction
true
give the formula for the Q10 method of estimating shelf life
t90 (T2) = t90(T1) / Q10 ^(diff in temp1 and 2/10)
t90(T2) = estimated shelf life
t90(T1) = given shelf life at given temp
what is the normal Q10 value for most drugs?
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