introduction to medicinal products part 3 Flashcards
what is a solution?
mixing two or more substances forming a single phase that are similar molecularly
what is one property about solutions?
they are clear
why are most pharmaceutical solutions water based?
water isn’t toxic and is cheap
why is tap water not used for pharmaceutical solutions?
may contain substances that will effect the solubility and stability of the drug
how is water purified?
distillation, ion exchange or reverse osmosis
what routes are solutions delivered?
oral, ocular, otic, nasal, pulmonary route, parenteral, topical, rectal
why do the requirements of solutions vary?
different routes of administration
what are the requirements for oral solutions?
palatable and viscosity should allow for pouring of the solution
requirements for topical solutions?
easy to transfer from container, should be able to attach to the surface without difficulty when removing
what are the requirements for ocular?
sterile, ph has to be close to 7.4 (ph of tears) so no discomfort is created, isotonic with tears so it doesn’t cause irritation for the eye or discomfort, appropriate viscosity for the eye
what ph can an eye tolerate?
3-9
why are non-aqueous solvents not used for all routes of administration?
unpalatable, toxic and doesn’t mix with other liquids.
what routes of administration are non-aqueous solvents used for?
intramuscular and topic
examples of non-aqueous solvents used?
esters and vegetable oil
what instances can non-aqueous solvents be used in?
when API is unstable and not soluble in aqueous solutions
what are the requirements for nasal solutions?
isotonic to fluids in the nose, ph 5.5-6.5, appropriate viscosity which is similar to mucus, taste masked in case its swallowed
what are the requirements for parenteral solutions?
sterile, isotonic when given in large volumes, appropriate ph to physiological ph so tissue necrosis doesn’t happen
what are the excipients used in solutions?
flavourings, colouring agents, antioxidants, ph adjusters, viscosity enhancers, isotonicity adjusters, antimicrobial adjusters, antimicrobial preservatives, solubility enhancers
what is the purpose of adding flavourings?
to make the solution more desirable for the patient to take
examples of flavourings used?
methanol, orange oil, lemon oil
what is the purpose of colourings?
makes the medicine more attractive to the eye (organoleptic properties) and should match the flavourings added
what is the purpose of atioxidants?
for stability
examples of antioxidants used?
sodium bisulphate and sodium sulphite
purpose of ph adjusters?
added to make sure the ph of medicine doesn’t cause irritation or discomfort or necrosis
examples of ph adjusters?
citric acid, buffers, sodium hydroxide
what are viscosity enhancers for?
to make solutions easier to handle and makes sure they stay on the site of administration for however long its required
examples of viscosity enhancers?
hydroxymethyl cellulose
what is isotonicity enhancers used for?
to make sure the solution is isotonic
what are antimicrobial preservatives used for?
they don’t allow the growth of microorganisms
examples of antimicrobial preservatives?
parabens, benzalkonium chloride
why is benzalkonium chloride not used nebulizer solutions but is used in oral solutions?
because it can cause bronchoconstriction
what are solubility enhancers for?
to keep the solubility of the drug constant and to improve it
what are suspensions?
solid particles within liquid because the solid doesn’t dissolve enough in the liquid
why do many drugs cause challengers when it comes to formulation?
they have low aqueous solubility because they fit in hydrophobic pockets of a receptor to actually work
what does a good suspension include?
the solid particles of the same size are evenly distributed in the liquid and stay like that for a long time so every dose of drug is the same therefore has the same effect on the patient
what is sedimentation?
particles being dragged downwards due to gravity pull
why is sedimentation a problem in suspensions?
solid particles aren’t evenly distributed so same dosage won’t be received by each patient
how to reduce the rate of sedimentation?
reducing the size of solid particles, increase viscosity of liquid, reduce density difference between particle and liquid
what instances can you and can’t you redisperse a medicine?
sedimentation- can shake to make a uniform suspension
caking- can’t redisperse even after shaking
what excipients are present in suspensions?
antimicrobial preservatives, buffers, chemical stabiliser, suspension agents, viscosity modifiers, flocculation modifier
what are buffers for?
keeps ph within a narrow limit
examples of chemical stabilizer?
ascorbic acid (vitamin C), EDTA
what are suspending density and viscosity modifiers for?
increasing density, reduces the rate of sedimentation
examples of suspending density and viscosity modifiers?
methylcellulose and hydroxypropyl cellulose are cellulose ethers
what are flocculation modifiers for?
reduces the number of floccules forming which are loose particles
why are suspension sometimes used for medicines for children over solutions?
because the taste of the drug isn’t as strong
how does ph control drugs?
effects the amount of ionisation which in turn effects solubilit
what percentage of drugs are weak bases?
75 percent
what is the purpose of a buffer?
so drug doesn’t cause irritation or necrosis at site of application
ensures stability of API and excipients used
ensure solubility in solutions
to subdue solubility in suspenssions
draw a graph on how percentage ionized, percentage of solubility differ between weak bases and weak acids
refer to slide 19
introduction to medicinal products part 3 ppt
what equation is used to calculate ionization of a weak acid?
pH= pK_a + (log_10 ([A^− ] )/[HA])
what equation is used to calculate ionization of a weak base?
pH= pK_a + (log_10 ([𝐵] )/[〖𝐵𝐻〗^+ ])
what does a buffer do in a solution?
maintains the ph when small amounts of acid or alkali is added
example of a buffer?
acetic acid and its salt
what is the name given for a buffer to handle changes in ph?
buffer capacity (β)
what is β equal to?
the moles of H+ needed to change 1 litre of buffer by 1 ph unit
when does buffer capacity increase?
when concentrations of substances increase
when is buffer capacity the greatest?
when ph=pKa of acid
examples of buffer solutions?
acetate, citrate and phosphate buffer
when can absorption occur in the gastrointestinal tract?
when drug is in solution
what are the biopharmaceutical considerations of drugs diagram?
slide 23
ppt introduction to medicinal products part 3
what order of bioavailability do drugs follow?
aqueous solutions > aqueous suspensions > solid dosage forms
which step does solution administration bypass?
disintegration
