3.3 Flashcards
The degree and speed of aggregation is partially determined by a _____
balance of interparticulate forces
Interparticulate forces include ____ which is the surface charges arising upon dispersal in aqueous medium (same identical molecule drug with same charge will be repulsive to each other)
electrostatic repulsive force
Interparticulate forces include ____ which is the arising from electromagnetic fluctuations in surfaces molecules (come together permanently - hard to separate)
Van der Waals attractive forces
Interparticulate forces include _____ which occur in sucrose crystals (with all of its hydroxyl groups) structuring of water near interfacial region
repulsive hydration forces
Combine all of the interparticulate forces there will be a net force of attraction and repulsion between two molecules which is displayed as a curve called
total potential energy of interaction curve
Particles may aggregate very strongly at close distances _____
primary minimum
Particles may aggregate very weakly at greater distances ____
secondary minimum
Two types of particle aggregation: ____+____
Coagulation (hard to separate) and Flocculation (weakly bound)
Potential energy of interaction curve may vary significantly based on ______ and the _______
nature of particles (charge) , medium that they are in
Particles will repel each other (less likely to come together at the primary _____
maximum
Coagulation are strongly bounded at the _____, the particles are closely aggregated making them difficult to disperse.
primary minimum
____ is the formation of a non-redispersible sediment within a suspension (combination of settling and coagulation)
Caking
De-flocculated particles are completely independent of each other and don’t have a ____ minimum
secondary
Deflocculated particles are pressed together from weight above and the repulsive energy barrier is overcome, leading to the aggregation at the ____
primary minimum
Formulators try to avoid caking by intentionally creating ___ suspensions.
flocculated
Flocculation is the weakly bound particles at the ____ minimum
secondary
little shake will disperse particles
How you store suspensions may lead to _____= growth of large particles at the expense of small ones.
Ostwald ripening
(1. small particles dissolve then supersaturate solution then recrystallize to larger crystals, 2. bridges between newly forming crystals occur resulting in large crystals)
Larger particles in suspensions will have (faster or slower) settling and (faster or slower) dissolution which leads to effect the bioavailability of the drug.
faster, slower
Ostwald ripening is accelerated by the ____ fluctuations.
temperature
alters solubility– avoid wide/repetitive temperature changes
