making a medicine Flashcards
what is a medicine
drug delivery system
what is a drug
active pharmaceutical ingredient (API); therapeutic agent
what is a formulation
recipe for making a medicine, including ingredients ingredients and processes
what is an excipient
ingredient that is not the drug ( a preservative)
what is a dosage form
physical form of the medicine (tablet or capsule)
what is pharmaceutics
science of medicine design and manufacture
what is preformulation
characterization of the drug
what is the rational formulation design
delivering the drug to the right site and making it useful
right dose
right place
right time
what is the aim of formulation
optimal drug delivery to the therapeutic target to maximize therapeutic efficiency and patient safety
* Drug properties, e.g. solubility, permeability, stability
* Route of administration, e.g. target specificity, local vs. systemic
* Use and patient need, e.g. infants, elderly, dexterity, consciousness
how can formulation enhance a medication, how are these enhancements achieved
drug delivery and targeting
processability and manufacturability
usability and user acceptability
stability
these enhancements are achieved using excipients and medical devices
what is lipinskis rule of five
molecular weight <500
log P <5
H-bonds donors <5
H-bonds acceptors <10
assumes absorption by passive diffusion
what is the formula of log P
log P= log (concentration in octane/ concentration in water)
why is log P important
it determines permeability across biological membranes (affects absorption and ultimately efficacy and safety)
affects formulation decisions
solvent choice
dosage form (emulsion, suspension or solution)
what affects solubility
solvent properties (polarity, PH)
solute properties (solid form, pKa)
temperature
pressure
why is solubility important
It affects drug dissolution and absorption
* It is a key factor that determines oral bioavailability (i.e. BCS)
* It underpins formulation decisions (e.g. excipient choice)
* Many drugs that are poorly water soluble may have increased solubility and
absorption in a fatty intestinal environment (e.g. after a meal)
* Understanding how solubility may change allows formulation stability to be
predicted, and measures to be implemented to modulate it
what is the importance of reformulation
determines the physiochemical properties of the drug:
compatibility and stability
ease of formulation (solubility)
processability (flow properties)
shows best formulation strategy such as suitable dosage form and route of administration
how to calculate molecular dissociation
look ay HA and PKA log calculations
why is molecular dissociation important
It affects drug solubility and absorption
Ionised form more water soluble, but non-ionised form better absorbed. It may vary with body site, e.g. different parts of the GI tract.
* Needs to be accounted for in deciding route of delivery and formulation
* May be leveraged (e.g. in enteric-coated formulations).
It can affect formulation instability
Ionised drugs may form insoluble precipitates with incompatible counter ions.
