Dosage form design I Flashcards
What are some rationales for drug design?
- Adding starch or lactose to enlarge the volume of the drug to ensure tablet is a compressible size
- colouring powder to make it more appealing to patients
- alter properties of tablet to ensure controlled release which would require less frequent administration from patient,
- base our drug design on the stability that is available to us
- formulating certain dosage forms for the convenience of the patient (e.g. tablets vs. suspensions)
why does there need to be rationale behind drug design?
biologically active entities are rarely administered as pure chemical substances due to issues with patient acceptability, therapeutic issues, toxicity, stability, etc. so they are given as a formulated preparation
these can vary from simple solutions to complex drug delivery devices
these are designed to help patients take and adhere to their medications
what do we aim to improve in all dosage forms?
taste appearance stability availability absorption
why do we need to improve availability in dosage forms?
you can only give some dosage forms to a certain age group
e.g. kids under 5 can’t really swallow tablets and may need suspensions which requires the right taste and colour.
why do we need to improve absorption in dosage forms?
Every drug must be absorbed into the body in order to have effect. we aim to enhance this.
e.g. Q10 is a drug which stimulates heart or organ function with little oxygen. It is very suitable for heart disease patients. However, it is poorly water soluble. If we want to enhance the bioavailability of Q10 we need to enhance its solubility. this can be done with microemulsions.
what makes up a drug?
the active compound and all its additives/excipients
What are the major components of a tablet?
active ingredient which is usually powder. This is usually a very small amount.
starch (cheap and common additive) used to make the tablet normal sized and compressible
other additives including buffer, flavourant, colourant, preservative, lubricant, thickener, etc.
What do we sometimes replace powder with?
granules
what is the dry method of making granules?
place powder directly into machine to form the pretablets
we cut this up to form the dry granules
we then compress these into tablets
What is the wet method of making granules?
mix powder and starch uniformly and then add water.
this is then seived through and collected to make the granules
What must occur if the granules are to be put into capsules?
they must be dried using temperature control
this depends on the type of compound you are using
Why is the transdermal patch used as a controlled release medicament?
It utilises a polymer to create a rate controlling membrane between the drug and our skin.
what are the main components of the transdermal patch?
Drug is contained in the patch.
Rate controlling membrane determines how much drug is released and goes into our blood stream
Adhesive layer keeps the patch on our skin
The drug is gradually released through the membrane, epdiermis, dermis and enters the blood vessels into the systemic circulation
what is a dosage form?
the clinical package in which a drug is presented to a patient
What are the two large families that pure powders belong to?
crystal (structured) in which atoms are arranged into a neat lattice. These have a high MP, BP and stability. This makes them difficult to dissolve
amorphous (irregularly dispersed). These have a low MP, BP and stability but are highly soluble
what properties do liquid crystals have?
some of liquids and some of crystals. They have some (but not all) of their atoms arranged neatly.