PPI lab midterm review

Absorption

the molecules cross the membrane interface to enter into the interior of a cell.

Adsorption

molecules of a substance (known as the adsorbate) attach to the

surface of a solid substance (known as the adsorbent).

adsorbate

liquid, solute in

solution or a gas which is adsorbed. The solid surface is also termed as an interface.

Physical adsorption(Physisorption)

is a physical process where the adsorbate is held to

the surface of the solid by weak, van der Waals forces.

desorption.

This type of adsorbate-adsorbent

interaction can be easily broken by changes in temperature and pH and the adsorbent is

easily regenerated.

Chemical adsorption (Chemisorption)

is a chemical process where a chemical bond (ionic,

covalent) is formed between the adsorbate and the adsorbent.

Adsorbents are typically classified into three types

Hydrophilic and polar oxygen-containing compounds such as silica gel

2. Non-polar carbon containing compounds such as activated carbon and

graphite

3. Porous polymer matrix with polar or non-polar functional groups

Activated charcoal is a

is a common adsorbent used in pharmacy and medicine. It can

adsorb a wide range of adsorbates (drugs and chemicals). It is used to treat toxicity due to oral drug ingestion.

Several factors influence adsorption

(e.g. temperature, layers, type of adsorption,

concentration of adsorbate, quantity of adsorbent. Temperature is inversely proportional

to adsorption.

The degree of the adsorbent ‘s affinity’ for the adsorbate determines its

distribution between the adsorbent and liquid phases. The extent of adsorption depends on several factors.

The properties of the adsorbate and adsorbent (affinity).

2. The surface area of adsorbent and active sites present on adsorbate (capacity).

3. The equilibrium conditions (temperature and concentration of adsorbate)

At low pressure, the extent of adsorption (x/m) varies

lineraly with the gas pressure

At moderate pressure, (x/m) varies

exponentially to gas pressure

At high pressure, (x/m) is

independent of gas pressure

The Langmuir isotherm is based on several assumptions.

Adsorption is a second order reaction (dependent on adsorbent and adsorbate

concentration.

2. The surface of the adsorbent is uniform and has a fixed number of active

(adsorbent) sites.

3. Adsorbate is adsorbed at the surface as a single monolayer. molecules of

adsorbate do not deposit on each other

4. One adsorbate molecule is adsorbed to only one single active site.

5. The adsorption is random and non-specific physio-adsorption via weak

forces (van der Waals).

Regression Analysis:

Analysis: Before performing the statistical analysis for goodness-of-fit, the

experimental data should be evaluated for errors (calculations, techniques).

Cylinder:

without turning on the Titrette, turn the sides wheels away from

you until the piston is around half way from the top

2. Make sure the red notch is horizontal from you. Turn the wheel

towards you to release the liquid back into the bottle. This removes

any air from the piston.

3. Repeat steps a) and b) again to make sure there is no air below the

piston, a few tiny bubbles are permissible

Suspension dosage forms

insolubility, stability, taste, and route of administration.

suspending agents and viscosity enchancers are required to

ensure controlled floccation and prevent caking

the particle size must be

fine to ensure uniformity of dose, prevent erratic absorptiom, bioavailability, and stability, avoid a coarse feeling in the mouth

Particle size increases

surface area and potentially bioavaialbility

extremely fine powders

defocculate due to an increase in surface charges, decrease in the wettability of the powder, increase caking

The suspension must be

physically and chemically stable

Physical stability

appearance, color, odor, taste, viscosity, specific gravity, uniform drug distribution, pH, sedimentation rate and volume, compability with container and cap

microbial stability

growth, color, odor

chemical stability

pH, degradation of active ingredient, viscosity change

suspensions must resist

microbial growth

preservative concentration is based on

non preserved water content in the suspension

aluminum hydroxides, trisilicates, magnesium oxides, and carbonates bentonite

are more likely to have microbial issues

simple syrup is

self preserving, require preservation due to their hygroscopic nature

recall syrups

are not preservatives

for oral preparations

citric acid and sodium citirate are preferred to maintain the pH

effectiveness of an anacid is determined by

its ability to neutralize gastric acid

suspensions

liquid preparations that consist of solid particles dispersed throughout a liquid phase in which the particles are not soluble

indiffusible suspensions contain insoluble powders that

don’t disperse evenly, form a sediment,

a well formulated suspension

doesn’t settle rapidly, redisperable, concentration in uniform, should not form a hard cake, must be easily porable, no micorbial growth, particles must be unofmr in size,

stokes equation can manipulate the sedimentation rate by

reducing particle size

increasing the viscosity

increasing the density of the external phase

particle size

insoluble solid powder must be reduced to small particles and dispersed in a continuous medium

generally used to reduce particle size

omminution, pulverization, and levigation

to stabilize suspensions, it is necessary to add

suspending/gelling agent to retard settling of the particles

viscosity enhancers

prevent settling of the insouble of the insouble particles

semi synthetic viscosity enhancers

methycellucose and sodium carboxymethyl cellulose

floccaulation

loose fluffly aggregates(floccules) of suspended particles

flocculation can be accomplished by

using charged molecules in their effective concentrations, prevents caking in suspensions

high flocculated suspensions

particles of a suspension settle too rapidly leading to physcial instability and lack of dosage uniformity in the product

surfactant ions absorb

on the surface of solid particles to neutralize surface chanrge

parenteral suspensions flocculation

modifying pH and through addition of electrolytes

highly charged drugs

flocculating agent is sleceted based on the type of charge on the suspended particle

potassium dihydrogen phosphate

anionic flocculating agent and useful for flocculation of postively charged (cationic) particles

deflocculation

replusion energy between the insoluble particles is high the collision between the same charged particles is opposed , particles repel each other and remain as discrete single particles

Bismuth subnitrate

is postive charged in weakly alkaline, neutral, and acid conditions

Bentonite

is negatively charged and postive charges on the surface of the benotonite and bismuth subnitrate, negative and positive charges on the surface of the benotonite and bismuth subnitrate molecules come together to form flocs

flocculated suspension

reversible sedmentation

settle fast

easily dispersible

eletronic potential between particles is low

aggregated particles behave like neutral groups

deflocullated suspension

irreversible sedimentation

settle slowly

not easily redispersible

eletronic potential between particles is high

charged particles