Lecture 2 - what is a medicine? Flashcards
What is the difference between a medicine and a drug?
A drug is an active pharmaceutical ingredient (API). It is responsible for the therapeutic affect of a medicine.
The medicine contains the drug plus everything else in the dosage form.
Examples of routes of delivery of drugs
- oral
- injections- bypass absorption
- implants
- topical and transdermal
- pulmonary
- nasal
- buccal and sublingual
- occular
rectal, vaginal
ULTIMATE AIM OF MEDCINE DESIGN
To get the right drug to the right place at the right dose at the right rate.
What is a dosage form?
The physical form of the medicine, which includes drugs and other ingredients.
Dosage form examples
tabs, caps, liquids, topicals, inhalers
Different dosage forms work at different rates. Give examples.
IV works in seconds
intramuscular/ subcutaneous injections and aerosols and buccal tabs work in minutes
caps and tabs, MR tabs, solutions and suspensions can take minutes to hours
enteric coated tabs (protects dosage form from being dissolved) can take several hours
depot injections and implants can take days to weeks
topical varies
What are drug delivery systems (DDS)?
A method of administering a pharmaceutical compound to achieve a therapeutic affect in humans/animals. These aim to get drug to specific target site.
Examples of DDS?
- controlled release
-transdermal patches which release a small amount of drug over a long period - injectable systems (IV and IM)
- nanoparticles and liposomes (deliver drugs at a cellular level)
What is drug absorption?
The uptake of a non-metabolised drug, following the release from its formulation/drug form, from the site of delivery to the system circulation (basically the drug crossing biological barriers into systemic circulation)
Outline the drug absorption in the GI tract.
- oral dosage form is swallowed.
- enters the stomach
- the dosage form either dissolves and releases drug into the stomach OR if enteric coated it will not break down in the stomach and instead moves to the small intestine.
- mesenteric veins are groups of veins in the abdominal cavity which drain blood from the intestines to the liver. The drug is absorbed into the mesenteric veins which join into the splenic vein and drains to the portal vein.
- blood travels to the liver.
- from the liver it travels to the heart.
- the drug then enters the systemic circulation and diffuses into tissues in the body and has intended effect.
Give overview of how drug is actually absorbed into gut epithelium .
- enters stomach
- solid dosage form dissolves into solution
- dissolved drug is absorbed into the gut epithelium
- the drug is then absorbed into blood and transported to the liver.
Does all of the drug make it through the gut epithelium?
no. some of the drug can be damaged and degraded by digestive and bacterial enzymes. pH and food can also cause difficulties. Efflux transporters (proteins) in the gut epithelium may also pump drug out of the epithelium.
Factors affecting absorption
- pH (affects solubility and ionization)
- hydrogen bonding (more hydrogen bonds= harder to break down)
- size
- lipophilicity = must have some to get into the membrane but not so much that it can get out.
What is bioavailability?
a measure of the quantity of a drug which reaches site of action and the rate that it gets there.
Why is working out the bioavailability of a drug useful?
used to assess how well a medicine performs and for comparing different dosage forms.
