Formulation Requirements Flashcards
what is the response with IV administration
large proximal vein, rapid response
what is the response with intramuscular administration
into a muscle, small volume of injection with fairly rapid absorption, can be used for controlled release formulations
what is the response with subcutaneous administration
into subcutaneous tissue, slower onset of action and absorption of drugs
can be used for implants
what does intradermal mean
between epidermis and dermis
what does intrathecal mean
into cerebrospinal fluid
what does epidural mean
outside the dura
what does intra-articular mean
into the synovial fluid of a joint cavity
what does intracardiac mean
into the muscles of the heart
what does intra-arterial mean
similar to IV but rarely used
what does intraocular mean
into the eye
what are the advantages of parenteral formulations
immediate physiological response, drugs with poor bioavailability used, unconscious or vomiting patients, control of dosage and frequency of administration, requirement for localised effect, correction of electrolytes, range of drug release profiles, total parenteral nutrition
what are the disadvantages of parenteral formulations
more complicated manufacture, skill needed for administration, pain on administration, allergy is rapid onset, difficult to reverse drug effects
what are the general requirements for parenterals
sterile, free from endotoxins and pyrogens, free from particulates
what physiochemical drug properties are needed for formulation
good solubility in solution, moderate solubility if using co-solvents, low solubility if in suspension
what drug peoperties are needed for IV products
aqueous solutions that do not precipitate in blood stream
what drug properties are needed for SC or IM products
suspensions (aqueous r oil based) and oil-based solutions, aqueous solutions
what are the colligative properties of formulations
vapour pressure lowering, boiling point elevation, freezing point depression, osmotic pressure
what are colligative properties
properties of solutions dependent on the ratio of solute particles to solvent particles in the solution, not the identity of the solute
what is vapour pressure depression
addition of non-volatile solute to a solvent, reduces vapour pressure above the liquid
results from some particles in the gas phase
what is boiling point elevation
dissolution of non-volatile solute in a solvent increases bp of solution with respect to that of pure solvent
change in T = Kb m
kb is bp constant
what is freezing point depression
dissolution of a non-volatile solute in solvent decreases the freezing point of the solution with respect to that of pure solvent
cange in T = Kf m
Kf is freezing point depression
what is osmosis
solvent from lower concentration solution will move through semi-permeable membrane to higher conc solution
what is osmotic pressure
external pressure that must be applied to prevent the movement of solvent via osmosis
what is the osmotic pressure equation for a non-electrolyte solution
V
n= moles, R= gas constant, t=temp, v=vol
what is the van’t hoff factor
osmotic pressure = icRT
i= given value, R=gas constant, t=temp, c=conc
what is osmolality
number of osmoles/kg of solvent
what is osmolarity
number of osmoles/litre of solution
what is the normal osmolality for blood
275 to 295 mOsm/kg
what is an isosmotic solution
conc of solution and intracellular conc are equal
what is a hyper-osmotic solution
conc of solution greater than intracellular conc
cell shrinks
what is a hypo-osmotic solution
conc of solution smaller than intracellular conc
cell swells
what is isosmoticity
two solutions separated by a semi-permeable membrane and there is no net movement of solute
what is isotonicity
two solutions separated by a biological membrane and remain in osmotic equilibrium
what is the difference between isomotic and isotonic solutions
a solution that is isosmotic with blood will only be isotonic if the blood cells are impermeable to the solute molecules and permeab;e to the solvent
what is osmoticity
property of solution and independent of any membrane
what is tonicity
property of solution in reference to a particular membrane
what solutions are not isotonic with biological membranes
ammonium chloride, urea, glycerine, propylene glycol
what terms are used for osmoticity if the membrane is impermeable to solutes
isosmotic = isotonic hyper-osmotic = hypertonic hypo-osmotic = hypotonic
what type of solution is preferred for parenteral preparation
isotonic
hypotonic can be adjusted with dextrose or sodium chloride
hypertonic solutions cannot be adjusted
what are the effects of excessive IV infusion of a hypotonic solution
RBC swelling, haemolysis, water ingress into cells/tissues, water intoxication leading to convulsion and oedema
what are the effects of excessive IV infusion of an isotonic solution
possible increase in extravascular fluid volume and circulatory overload
what are the effects of excessive IV infusion of a hypertonic solution
hyperglycaemia, intracellular dehydration, osmotic diuresis, water/electrolyte loss, dehydration, coma
also RBC creatination, low bp, shallow respiration, pulmonary oedema, haemorrhage
what injection routes require isotonic solutions
intraspinal/intrathecal injections, intradermal injections, intramuscular and subcutaneous injections (hypertonic can increase IM drug absorption)
what does TPN stand for
total parenteral nutrition
what is the osmolarity method of preparing isosmotic solutions
- calculate osmolarity of components
- determine remaining osmolarity needed to make solution isotonic with body fluids
- calculate amount of adjusting substance required to make up the shortfall
what is the freezing point of bodily fluids
-0.52 degrees C
how to calculate freezing point depression
freezing point depression constant is 1.86 for water
overall, Tf from all components must be 0.52 degrees C
what is the NaCl equivalents method
the sodium chloride equivalent of a solute is the mass of NaCl that lowers the freezing point of a solvent to the same extent as 1g of the solute
what is the White-Vincent method
water added to the drug and excipients in a sufficient amount to form an isotonic solution
preparation is then diluted to final volume with an isotonic or buffered isotonic diluting vehicle
which calculation method is inaccurate
osmolarity method
it is just an estimation
what is the molecular weight of NaCl
58.44
what are the ideal conditions for an isotonic solution
freezing point -0.52
0.9% NaCl
285 mOsm/L
the membrane must be impermeable for solute isotonicity
