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Pharm 124 Solutions Exam
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Pharm 124 Solutions Exam With Complete Solutionwhat is the definition of a solution? - ANSWER a chemically and physically homogenous
mixture of two or more substances
what are the 3 classifications of solutions? ex what are they based on? - ANSWER 1. based on
the nature of the particles (true solutions, colloidal soln, or dispersions)
2. based on route of administration
3. based on solvent/dispersion medium (aq or non aq)
what are the advantages of solution dosage forms? - ANSWER provide completely
homogeneous doses
doses are easily adjusted
immediately available for absorption and distribution
can be use by any route of administration
can easily be administered to patients unable to swallow caps or tabs (children's dosing)
what are the disadvantages of solution dosage forms? - ANSWER chemicals have lower
stability in solution
drugs may not be soluble in acceptable solvents
solutions may provide suitable media for microorganism growth (requires additional
preservatives)
increased problems associated with handling. packaging, transporting, storage
oral dosage forms may require additional additives/techniques to mask taste
solutions are generally provided in multiple dose containers requiring measuring (less
accurate)
,what is dissolution? - ANSWER The transfer of molecules or ions from a solid state into
solution
dissolution rate doesn't = solubility
high solubility is typically associated with high dissolution rate
what are the 3 steps of dissolution? - ANSWER 1. Interfacial reaction: solid becomes molecules
of solute
2. Moving into the liquid and replacement with solvent molecules
3. diffusion through the boundary (stagnant layer) surrounding the particles
Gibbs free energy equation - ANSWER ΔG = ΔH - TΔS
gibbs free energy is negative for spontaneous processes
delta S is usually positive for dissolution = entropy change
Fick's Law - ANSWER migration of solute through stagnant layer is driven by concentration
different between the surface of the solute and the bulk solution
(dC/dt)= kΔC = k(Cs-C)
Noyes-Whitney equation - ANSWER describes dissolution of spherical particles
(dm/dt) = [k1A(Cs-Ct)/h]
dm/dt - rate of mass transfer of the solute
, A - surface area of the particle
h - thickness of diffusion layer
Cs - saturation of concentration of the solute
Ct - concentration of drug in bulk solution at time t
k1 - diffusion coefficient (also called D)
note K=k1 (or D) /h
K = dissolution rate constant
what are Factoring affecting dissolution rate? - ANSWER surface area of solid
- area is inversely proportional to particle size
- dispersibility ; use of wetting agent
solubility of solute (Cs)
- factors that affect solubility will impact dissolution rate
(T, solvent, Solute structure, polymorphic form. additives)
thickness of stagnant later (h) ; inversely proportional
-can decrease with stirring
diffusion coefficient k1 (sometimes called D)
-stokes; Einstein equation: D = kT/6(pi)n
what is the aim for dissolution testing? - ANSWER to measure the rate at which the drug
substance is released from the dosage form and dissolve in a particular dissolution medium
what are the 2 main uses of dissolution testing? - ANSWER 1. to assess the quality of solid drug
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