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56 Cards in this Set
- Front
- Back
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What 4 factors are involved with oral drug administration?
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1. mechanisms of drug absorption
2. GI transit 3. physiological constraints 4. drug-related properties |
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Definition of solutions
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A HOMOGENOUS MIXTURE that is prepared by DISSOLVING a solid, liquid or a gas into another liquid and represents a group of preparations in which the molecules of the solute are DISPERSED among those of the solvent
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Why is homogeneity important?
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It ensures that each volume of the solution contains the same amount of drug so that we know the patient is receiving the required amount
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What is unique to solutions in terms of dissolution/absorption
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The solute is fully dissolved in the solution so that the dissolution step is skipped during administration --> faster absorption
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Examples of aqueous solutions
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Douches
Enemas Gargles Mouthwashes Juices Nasal solutions Otic solutions Irrigation solutions Syrups Honeys Mucilages Jellies |
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Where is a douche used and what is its function
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-used in a cavity of the body
-functions as an antiseptic cleansing agent |
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Where is a gargle used and what is its function
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-used to treat the nasopharynx
-also used to help in neck region to treat or prevent infection |
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What is the advantage of using glycerin in solutions?
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the high viscosity allows the drug to be retained in the ear canal for a longer period of time
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Where is an irrigation solution used and what is its function
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-treats body cavities not naturally created (e.g. surgical incision, wound)
-used to sterile |
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Define non-aqueous solutions
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These solutions are based on percent organic solvent in solution (5-10%) whereas aqueous solutions are 100% water-based
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When are non-aqueous solutions used?
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When the solubility of the drug needs to be improved by incorporating non-aqueous excipients
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What are some examples of non-aqueous solutions
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Collodions
Elixirs Glycerins Inhalations/inhalants Liniments Oleovitamins Spirits |
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What are collodion solutions and its function?
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-contain ethylether and ethanol mixture that evaporate off the skin, leaving behind the active ingredient
-used as a keratolytic agent for the treatment of warts |
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What are elixirs and its function?
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-sweetened alcoholic liquid
-small amount of alcohol improves solubility of drug |
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What are inhalants and its function
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-drugs with non-aqueous base (e.g. alcohol)
-helps to penetrate down the respiratory tree |
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What are liniments and its function
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-mixtures of various solutions (alcohol + oil)
-helps penetrate skin area -unlike elixirs, they are used externally |
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Properties of solutions?
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1. solutes - can be divided into non-electrolytes and electrolytes
2. solvents - true solution, colloidal dispersion, coarse dispersion, ideal solution, real solution |
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Define a true solution
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a mixture of two or more components that form a homogenous molecular dispersion i.e. a one-phase system
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Define a colloidal dispersion
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represents a system having a particle size intermediate between that of a true solution and a coarse dispersion (10A to 5000A)
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Define a coarse dispersion
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diameter of the particles in emulsions and suspensions for the most part being larger than 1000A (0.1um)
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What are the properties of non-electrolyte solutes
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-they are substances that do not yield ions when dissolved in water
-do not conduct a electric current -colligative properties are fairly regular (i.e. a 0.1M solution of non-electrolytes produces same colligative effect of another non-electrolytic solution of equal concentration) |
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What are the properties of electrolyte solutes
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-form ions in solution
-conduct electric current -show apparent irregular colligative properties -divided into strong and weak electrolytes |
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What are the differences between strong and weak electrolytes
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Strong: completely dissociate in water
Weak: partially dissociate and in equilibrium |
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What do the colligative properties of solutions depend on?
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Mainly on the number of particles in a solution
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What are colligative properties?
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-changes in vapour pressure (osmotic pressure)
-freezing point depression -boiling point elevation |
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What are additive properties?
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-depends on the total contribution of the atoms in the molecules
-e.g.molecular weight involve adding the masses of the constituent atoms |
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What are constitutive properties
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-depends on the arrangement, number, type of atoms within a molecule
-e.g. refraction of light, electric properties, surface and interfacial characteristics, |
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What is an ideal solution?
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-a solution in which there is no change in the properties of the components, other than dilution, when they are mixed to form the solution
-no heat when mixing -final volume is additive -mixing substances with similar properties form ideal solutions |
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What is escaping tendency?
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-if one body is heated to a higher temperature than another, heat will flow "downhill" from the hotter to the colder body until both bodies are in thermal equilibrium
-hotter body has a greater escaping tendency than colder one |
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What is Raoult's Law?
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-quantitative expression of escaping tendency
-the partial vapour pressure of each volatile constituent is equal to the vapour pressure of the pure constituent multiplied by its mole fraction in the solution |
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Describe the negative deviation for Raoult's Law
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-attractive forces between molecules of DIFFERENT species are greater than between molecules of individual species (e.g. H-bond)
-escaping tendency is reduced |
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Describe the positive deviation for Raoult's Law
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-interaction between A and B molecules is less than A-A and B-B
-presence of B molecules reduce the interaction of the A-A and vice versa -results in greater escaping tendency of A alone and B alone (increased vapour pressure) |
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Where is Raoult's Law and its deviations important?
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volatility and BP can change which can also change the pharmacological activity
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Define suspensions
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-a COARSE DISPERSION in which INSOLUBLE SOLID PARTICLES are dispersed in a liquid medium
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Purpose of suspensions
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-want slow absorption to get a constant plasma level
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3 Physical properties of a well-formulated suspension
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-must remain sufficiently homogenous between shaking the container and removing the required dose
-sediment must be easily resuspended by the use of moderate agitation -viscosity must not be so high that removal of the product is not difficult -suspended particles should be small and uniformly sized in order to give a smooth, elegant, non-gritty texture |
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Pharmaceutical applications of suspensions
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-patients have difficulty swallowing
-prevents degradation in the presence of water -adsorptive properties of fine powders used in inhalants -masking of bad taste -topical applications -control rate of absorption/dissolution (by altering particle size) -vaccines are suspensions |
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Suspension ingredients
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-solute
-solvent -preservatives -antioxidants -suspending agents -dyes -wetting agents |
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How do suspensions prevent degradation of drugs
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-some drugs hydrolyze easily in water so cannot be formulated as aqueous solution
-synthesize insoluble derivative to be formulated as a suspension -can also use non-aqueous base (e.g. coconut oil) |
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Different types of suspensions
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-gels
-lotions -magmas and milks -mixtures |
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What is the consistency of gels
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semisolid
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What are gels made of
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small inorganic particles or large organic molecules interpentrated by a liquid
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What is a two-phase gel system
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gel mass consists of a network of small discrete particles
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Are gels thixotropic? If so, what does it mean?
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yes, and they liquefy upon agitation and become gels upon standing
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Should gels be shaken prior to use?
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Yes
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What is a single-phase gel system
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organic macromolecules distributed uniformly throughout a liquid where no apparent boundaries exist
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Can natural gums be found in gels?
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Yes
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What are single-phase gels containing natural gums
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mucilages
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What are lotions
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liquid suspensions or dispersions intended for external application to the body
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What are the properties of lotions
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-finely powdered, insoluble solids held in a permanent suspension by suspending agents and surface active agents
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Do lotions tend to separate on long standing?
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yes - require a shake well label
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What are magmas and milks
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aqueous suspension of insoluble, inorganic drugs and differ from gels mainly in that the suspended particles are larger
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Properties of magmas and milks
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thick and viscous
no need to add a suspending agent |
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What are suspending agents
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-thickens the formulation to help keep particles suspended
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What is a caution with using suspending agents
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can react to drug substance
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What is a common suspending agent
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carboxymethylcellulose
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