L33 Suspensions TJ and GT Flashcards
Advantages of suspensions?
Does not require water Can give rapid local action Easy to swallow Better compliance with elderly + children Dose can be altered by volume measured
Disadvantages of suspensions?
Stability issues (chemical. physical. microbial)
Interactions with other drugs or chemicals in the body
Degradation issues
Phase separation
Sedimentation
Crystal growth
packaging issues
All of which affect the dosages administered
Are there issues with packaging? if so what
Glass containers or certain plastics can be more expensive than typical formulations
Packaging process is also slower
Suspensions are often heavier and this results in transporting products via larger machines, resulting in an increase in cost.
What are the characteristics of a good suspension
- no sedimentation
- no phase separation
What are the characteristics of an adequate suspension
High flocculation volumes which are acceptable, because upon shaking, the suspension can be reconstituted; the suspension can be controlled
What are the characteristics of an unacceptable suspension
Completely sedimented and total phase separation has occurred. Coagulation occurs, no flocculation and no reconstitution takes place upon shaking the bottle. It’s caked.
What is a pharmaceutical suspension?
A dispersion of solid particles in a liquid to make on homogeneous phase. Drug particles are suspended between 1-100 microns. When moderately shaken it will pour out easily.
What is a structured vehicle used for?
A structured vehicle can be used which opposes coagulation and sedimentation. The drug cannot aggregate/sediment if trapped in a gel network.
How can a structured vehicle be achieved?
By suspending discrete particles into a structured vehicle OR using a flocculating agent (examples include electrolytes like KCL)
what does stokes law of sedimentation aim to illustrate?
That the velocity of sedimentation is directly proportional to the viscosity of the suspension. Thus, the greater the viscosity, the lower the velocity of sedimentation
how do we achieve NO sedimentation in theory? comment on the ease to achieve this
if densities of the solid and liquid are equal, the velocity of sedimentation, v, is 0. This is very hard to match, additionally, Density is temperature dependent , meaning that the density of the vehicle would not match the liquid at some temperatures.
What feasible methods are there to lower sedimentation velocity?
reduce particle size, because below a critical particle size, brownian motion predominates over sedimentation
if particles are irregular, it is less likely to sink
Increase viscosity can hinder rate of sedimentation
Repulsion of ions can occur to stabilise a suspension. Steric repulsion > electrostatic because it is less susceptible to electrolytes, and pH changes
What is the name given to ideal suspension fluids? state characteristics with rheology
Thixotropic suspension fluids. They are viscous in the container. The suspension will thin upon shaking and remain pourable. When left to stand, it will thicken again.
Coagulation vs flocculation difference?
Coagulation is essentially irreversible. When in conjunction with sedimentation, it is known as caking
Flocculation however is reversible
what are the components of a suspension?
drug
water
suspending agent e.g microcrystalline cellulose MCC
dispersant (if drug is hydrophobic)
