Stability of pharmaceutical dosage forms (II)

Mathematical study of the rate of appearance or disappearance of a substance in a reaction process

chemical kinetics

WHY DO I HAVE TO KNOW THE RATE OF REACTIONS

1. rate or speed

2. time

3. stability and expiration date

4. appropriate rate

5. acting in timely manner

6. appropriate time frame

Rate is experimentally determined by measuring _________________________.

disappearance of drug or appearance of product

The rate of first-order reaction is directly proportional to the concentration of the reactants

first-order reaction

Most pharmaceutical reactions are of ______________

first-order

The amount of drug removed/degraded in a certain time interval _______________ with time. Unique to first-order reactions

decreases

The unit of first-order rate constant (k1) is

time^-1

Value of k1 is the ______________ of concentration of drug removed during a unit length of time.

fraction

The first-order rate constant fraction or % of drug degraded/removed in each time interval remains _______________

constant

It is not desirable for _____________________ to operate via first order reactions

1. sustained drug delivery

2. TDDS

3. implants

The time taken for amount or concentration of drug to decrease by one half or The time needed for drug concentration to decline to half of the initial concentration

half-life for first order reactions

For first-order process, half-life depends only on _________

first-order rate constant (k1)

The half-life of a first-order reaction is not __________ on drug concentration b/c it's a constant

dependent

The rate of reaction is constant and ___________ of the concentration of the reactants

independent

Degradation of drug _______________ generally follow zero-order kinetics

suspensions

Zero-order process is desired for sustained drug delivery systems including: ____________

TDDS, implants, etc

For zero-order rate constant the amount of drug removed/degraded/lost in a certain time interval remains ___________

constant

the unit of zero-order reaction rate constant is __________________

concentration per time

________________ of zero-order processes is NOT a constant

Half-life

the time after manufacture or preparation until the product contains 90% of its original strength

Shelf-life

shelf life is the time period at which we have at least 90% of the______________ in the formulation

labeled drug

That means within the shelf life we should have not _____________ of original drug as degraded

more than 10%

shelf life is indicated as

t90

Remaining percentage of labeled strength

chemical shelf life

Dissolution rate, Integrity of dosage forms (Particle size and homogeneity in emulsions, Re-dispsersibility of Suspensions, Integrity of Suppositories)

physical shelf life

Color, Odor, Texture of drug product

Aesthetic