L2: What is a medicine? Flashcards
what is drug absorption?
the uptake of non-metabolised drug, after release from its formulation, from the site of delivery to the systemic circulation
what are the routes of delivery? (9)
- oral
- injections (intravenous/muscular/dermal, subcutaneous)
- implants
- topical and transdermal
- pulmonary (inhalation)
- nasal
- buccal and sublingual
- ocular, otic
- rectal, vaginal
what is the aim of medicines design?
to get the right drug to the right place at the right dose and at the right rate
what does this depend on (aim of med designs)?
- type of drug and situation/case
- physical/chemical properties of the drug and dosage
what else do you control if you control the rate and extent of absorption?
the onset, duration and intensity of biological effect, and the +ve effect on the patient
What is a drug?
- drug is the active pharmaceutical ingredient (API), the chemical moiety in a medicine which is responsible for the therapeutic effect
What is a medicine?
API plus excipients
- dependent on the dosage form and desired drug release
what is dosage form?
the physical form in which medication is produced and administered
types of dosage forms (5)
- tablets
- capsules
- liquids
- topicals
- inhalers
what are major considerations in design of dosage form? (3)
- the physiochemical properties of the drug
- biopharmaceutical considerations
- therapeutic considerations of the disease state and patient to be treated
what are biopharmaceutical considerations?
- how the administration route of a dosage form affects rate and extent of drug absorption into the body
what do therapeutic considerations determine? (4)
- most suitable type of dosage form
- possible routes of administration
- the most suitable duration of action
- dose frequency
what are enteric coated formulations?
layer of protection on the medicine that prevents it from being dissolved in the stomach
what is drug delivery system (DDS)?
method of delivery of the drug (pharmaceutical compound) to achieve a therapeutic effect
what are examples of DDSs? (4)
- controlled-release systems
- transdermal patches
- injectable systems
- nanoparticles and liposomes
what are the steps in drug discovery and pre-clinical development? (6)
- target identification and validation
- drug screening -> hit/lead compound
- lead optimization
- formulation development
- pharmacokinetics and toxicity
- clinical development
drug absorption in the GI tract
oral delivery:
- swallowed
- into stomach (dissolved w/o coating)
- into small int. (dissolved w/ coating)
- into ascending, transverse and descending colon
- excreted if not dissolved and absorbed
what veins do the intestines go into?
Inferior mesenteric vein
- transverse colon
- descending colon
superior mesenteric vein
- small int.
- ascending colon
into the portal vein into the liver
Steps of drug absorption in the GI tract
- solid breaks apart
- particles dissolve forming solution
- absorption across epithelium
What are some problems with the drug absroption in the GI track?
- digestive/bacterial enzymes can damage them
- efflux: metabolic enzymes can pump out the molecules as a for of protection from potentially harmful molecules
What are factors that affect absorption of small drugs? (4)
- pH: ionises, solubility
- hydrogen bonding (must be broken)
- size: greater size = greater time of absorption
- lypophilicity: has to be balanced so can go in and out of cells
What is pharmaceutics?
The science of making medicines
What is biopharmaceutics a study of?
The interaction of the medicine with the biological system, allowing the optimisation of DDS
What does biopharmaceutics includes? (7)
- chemistry: organic and physical
- chemical analysis
- physical tests
- pre-formulation and formulation science
- disintegration, liberation and dissolution tests
- bioavailability studies
- bioequivalence studies
What is bioavailability?
Measure of the quantity of drug which reaches its site of action and the rate at which it gets there
What is the equation for bioavailability?
F = Fa x Fg x Fh
F: net oral bioavailability
Fa: fraction absorbed
Fg: fraction escapoing GI
Fh: fraction escaping hepactic metabolism
What is pharmacokinetics?
What the body does to the drug
What is pharmacodynamics (PD)?
What the drug does to the body
What are the determinants of pharamacokinetics?
ADME
- liberation
- absorption
- distribution
- metabolism
- excretion
Plasma conc vs time (oral administration)
Duration of action: when the conc of drug in plasma is above minimum effective conc (MEC)
- therapeutic range
