pharmacodynamics - drug formulation Flashcards
(19 cards)
why is drug formulation important?
drug must be formulated in a way that is acceptable to the patient and has the desired pharmacokinetic/dynamic properties, also impacts possible administration methods (+ vice versa)
how does drug formulation impact administration?
how can the drug physically be taken? this depends on its form - is it a solid, solution, suspension, tablet, cream, gel, etc
how are insoluble drugs formulated?
many drugs aren’t soluble in their neutral forms, this means they will not dissolve in body
drugs containing acidic/basic functional groups are often administered as a salt
this helps purification by imparting crystallinity, as salts are solid, improving solubility and increasing stability
polymorphism definition
exhibited when a compound/salt can exist in more than 1 crystalline form (= polymorph)
how does polymorphism of a substance affect drug properties?
different polymorphs have different melting points + solubilities - this must be considered to ensure it is appropriate for the physiological conditions - generally the most thermodynamically stable polymorph (with the highest melting point) is preferred for the API as it wont isomerise into another polymorph upon prolonged storage
what makes up a tablet/pill?
5-10% = the API/drug
80% = fillers, lubricants, binders which make up bulk of pill + hold it together
10% = disintegrants, ensures pill can dissolve in stomach/intestine
enteric coating definition
a coating used on pills to prevent dissolution in stomach
how do enteric coatings work?
they’re made of pH sensitive polymers that do not degrade at low/acidic pH such as in stomach
why are some pills coated in sugar/wax?
to mask any unpleasant taste
why do drugs have tamper proof packaging today?
because of the tylenol murders
what makes up a capsule pill?
capsule made of gelatin/hypromellose (plant based)
drug inside either as dry powder (increasing solubility) or microtablet (decreasing solubility)
why are lysosomes used to deliver some drugs?
allows more fragile drugs to be protected for longer e.g. COVID vaccine
liposome definition
a vesicle containing drug that acts as a carrier - made up of a hydrophilic core + hydrophobic shell
why are slow-release methods beneficial for oral drugs?
every time an oral drug is taken, it has the same lag phase, causing spikes in plasma concentration that can have undesirable effects - slow release drugs avoid this, as it allows the concentration of the drug to average out and consistently be at a certain level
what are 3 methods for making slow-release drugs?
osmotic pump
semi-permeable membrane
microencapsulation
how does the osmotic pump slow release method work?
drug is dissolved with a water-swelling polymer, both in anhydrous form, coated in enteric coating, with a small hole drilled into it
when drug is taken water slowly moves into tablet through hole causing polymer to swell and as a result the drug is pumped out of the hole over time
how does the semi-permeable membrane slow release method work?
similar to a skin patch
drug slowly diffuses through the membrane
how does the microencapsulation slow release method work?
minute particles of liquid/solid drug are coated with a film and many of these are packed into a normal pill capsule
depending on the material of the film, the microcapsule will be dissolved and drug will be released at a particular place in the body/time after administration
give one other advantage of microencapsulation
as well as enabling slow release, it also allows masking/protection of drug and reduces volatility
