Pharmacuetics Flashcards
What is the importance of powder mixing?
For all solid forms
Content uniformity
Therapeutic effect
Patient safety
What are the challenges of powder mixing?
Homogeneity is difficult to achieve
Demixing can occur
Overmixing causing degradation of preparties can occur
Types of mixtures?
Positive mixture Negative mixture Neutral mixture Perfect mixture Random mixture Ordered mixture
What is powder homogeneity?
A random mixture. assessed using statistical approach
How is powder homogeneity assessed?
Sample size
Scale of scrutiny
Types of mixers?
Tumbling mixer Agitator mixer Shear mixer Fluidised bed mixer Static mixer
Tumbling mixer
Particles set in motion by rotation of mixing vessel. particles move in mixer due to gravity (free flowing)
Performance affected by: Fill volume (max 60%) Residence time Rotation speed Inclination angle of mixer
example of tumbling mixer = Turbula mixer
Shear mixer
High velocity rotating blades High shear forces Break up agglomerates Shear and diffusive mixing Often as mixer-granulator Unsuitable for friable materials
in other words it works like a blender
Nauta mixer
An orbital agitator mixer
Contains a rotating screw in a conical vessel
Screw rotates axially and orbitally
Fluidised bed mixer
High velocity ait forced through powder bed disperse particles
suitable for friable powders because its gentle
Static mixer
No moving parts
Powder flows through motionless mixing elements
Suitable for continuous processing
Practical considerations
Ensure mixer matches material property
Ensure appropriate mixing time and mixing mechanism
Determine appropriate mixing time and monitoring mixture at intervals
Static causes clumping due to electrostatic interactions
What is an excipient and its purpose?
Non intended therapeutic function
intended to categorise and enhance the formulation
Ideal excipient properties?
Inert (elicit no biological response)
Safe
Quality assured
Economical
Excipients for powder mixtures
Diluent Binder Disintegrant Glidant Anti-adherent Lubricant
Lactose, starch, cellulose, talc, colloidal silicon dioxide, magnesium stearate
