Biopharmaceutics 3 Flashcards
(14 cards)
What are the methods to improve the dissolution of poorly soluble drugs
Lipid based formulations
Size reduction technology
Functional polymer technology
Porous microparticle technology
Hydrophilic solubilization
Controlled precipitation technology
Inclusion complexes
Solid dispersions - fusion method, solvent evaporation method and melting solvent method
eutectics
What do lipid based formulations include
lipid solutions , surfactants, micro-emulsions and may contain a hydrophilic co-solvent
Lipid solutions consist of what?
a drug dissolved in vegetable oil or in triglycerides
the high lipophilicty facilitates drug absorption
The presence of surfactant in this formulation causes the enhanced absorption due to membrane induced permeation changes.
Surfactants also stabilize the emulsion and protect droplets against aggregation.
Co-solvents increase the solubilization of incorporated drugs.
Size reduction technology - how is it accomplished
by micro-ionisation, milling (impact and attrition), grinding, and supercritical fluid technology
Functional polymer technology - how does it enhance dissolution
this enhances dissolution rate by avoiding the lattice energy of the drug crystal
the drug interacts with the resins, which makes a resinate drug complex
Resinate interacts with HCl in stomach and ion exchange releases drug.
Porous micro particle technology - what is it
the poorly water soluble drug is embedded in a micro particle which has a porous water soluble sponge like matrix
when it is mixed with water, the metric dissolves and wets the drug which leaves a suspension of rapidly dissolving drug particles
This is the core technology applied as HDDS (Hydrophobic Drug Delivery System).
Hydrophilic solubilisation
The hydrophilic solubilization technology (HST) for poorly soluble drugs uses a lecithin and gelatin-based water-soluble coating to improve dissolution and hydration. Coat forms micelles which improve oral bioavailability of the insoluble drugs.
Controlled precipitation - how does it work
the drug is dissolved in a water-miscible organic solvent and then dispersed into aqueous medium containing stabilizers (HPMC, cellulose ethers, gelatin)
solvent dissolves in water and causes precipitation of the drug in the form of micro-crystals
stabilizers control particle growth and enhances the dissolution rate of poorly soluble drug due to large surface area, hydrophilized by the adsorbed stabilizer.
Inclusion complexes
Uses β-cyclodextrin and HP-β-CD to improve dissolution
outer surface is hydrophilic
inner surface is hydrophobic
Solid dispersions - fusion method - melting
the physical mixture of a drug and water-soluble carrier is heated directly until it is melted, which is then cooled and solidified rapidly in an ice bath.
To facilitate faster dissolution, the melt is poured in the form of a thin layer onto a stainless-steel plate and cooled by flowing air or water on opposite side of plate.
The final solid mass is then crushed, pulverized and sieved.
Solid dispersions - solvent evaporation method
Solid solutions or mixed crystals can be prepared by dissolving a physical mixture of two solid components in a common solvent, followed by evaporation of the solvent.
Thermal decomposition of drugs or carriers can be prevented because of low temperature.
Solid dispersions - melting solvent method
The drug is first dissolved in a solvent and then the solution is incorporated directly into the melt of the carrier.
A liquid drug such as methyl salicylate, Vitamin-E, clofibrate can be formulated as a solid dosage form and mixing it with melted liquid of PEG-6000 and cooling the mixture.
What is Eutetics
You take a mixture of two or more phases at a particular composition of materials that have the lowest melting point, at which temperature the phases will simultaneously crystallise
