F9 Introduction to pharmacokinetics (ADME) Flashcards
(39 cards)
what is pharmacokinetics?
- the movement of the drug (ADMET)
what is pharmacodynamics?
- the effect of the drug on the body
how can drugs access their target sites?
direct to site
- easy for skin, eye, gut, lung
- much more difficult for other sites but can be done
indirect
- via systemic circulation (blood)
- introduces problems of loss or dilution
- how will drug reach target site only?
- certain body places can only be accessed through systemic circulation
what does the umbrella term ‘elimination’ involve?
- metabolism
- excretion
what are the main routes for drug administration?
- inhalation
- oral
- injection
- transdermal
- rectal
what is the inhalation administration method of drugs preferred for?
- gases
- volatiles
what is the oral administration method of drugs preferred for?
- tablets
- capsules
- solutions
- buccal
what is the injection administration method of drugs preferred for?
- intravenous
- intramuscular
- subcutaneous
- intrathecal
what is intrathecal administration of drugs?
- in the spinal cord into the spinal fluid
what is the transdermal administration method of drugs preferred for?
- patch
- cream
what is absorption in ADME and what routes of administration require this?
- drug must enter the bloodstream from the site of administration
- all routes other than intravenous injection require an absorption step
what is the site of absorption for oral administration?
somewhere along the GIT
what is the site of absorption for transdermal administration?
across the skin
what is the site of absorption for hypodermic injection administration?
from injection site (muscle, adipose tissue)
what is the site of absorption for lung administration?
- alveolar surface
what feature makes molecules more likely to passively diffuse across a lipid bilayer?
more lipophilic = more likely to passively diffuse
describe the distribution step of ADME
- drug travels in systemic circulation after absorption
- perfuses all organs and tissues of the body
- closed system: drug makes continuous and multiple passes around the body and allows drugs to reach organs due to passing through continuously
what determines drug distribution?
- drug binding to plasma proteins
- structure of vascular endothelium
- accumulation in tissue depots
how does the drug binding to plasma proteins affect drug distribution?
- reversible binding can ferry drug around the circulation
- very high affinity binding can limit escape from the plasma and limits ability of drug to into the tissues
how does the structure of vascular endothelium affect drug distribution?
- there are pores between endothelium cells in most vessel beds
- some special cases = blood brain barrier and placenta
describe the blood brain barrier in terms of distribution
- capillary cells into brain have tightly packed endothelial cells and have an additional layer of these cells
- this makes the access to the brain tightly regulated
describe the placenta in terms of distribution
- has the capacity to protect the foetus from harmful components of the blood
how does the accumulation in tissue depots affect drug distribution?
- protein binding sites (including target!)
- adipose tissue
state the body parts in the highly-perfused lean tissue group
- blood cells
- heart
- lung
- liver
- kidney
- glands
- brain
- blood-rich organs so lots of blood gets to these
