FoM:L3 - Pharmacokinetics 1, administration and absorption Flashcards
What are the 4 main factors in pharmacokinetics? Briefly outline each one
Absorption - outside the body into the blood
Distribution - blood into extravascular tissue
Metabolism - back into blood/metabolites
Excretion - from the blood to outside the body
What are the main routes of drug administration?
- local: topical
- systemic: enteral or parenteral
What is the function of an enteric coating?
prevents disintegration in the stomach
What are extended release drugs?
- tablets have been modified so drug is slowly released through permeable membrane
- reduce frequency of dosing
What are parenteral formulations?
- injectables
- liquid or lyophilised
What are the types of topical formations?
- cutaneous
- inhaled
- eye/nasal drops
- implants
- suppositories
Where do most oral drugs get absorbed?
- small intestine
- except alcohol and aspirin
- rate impacted by whether food has been eaten as well as if liquid/solid meals
What is the pathway of an oral drug?
- absorbed in stomach/small intestine
- travel to the liver
- reaches general circulation
What is first-pass metabolism?
- first time a drug passes through the liver before entering systemic circulation
- affects bioavailability
What enteral routes avoid first-pass metabolism?
- buccal
- sublingual
- rectal
What are the types of parenteral administration?
- IV - instantaneous
- IM - intermediate
- SC - slow
all avoid 1st-pass metabolism and GI tract
What are the topical routes of action?
- transdermal - slow, lipophilic drug
- inhaled - rapid, low dose, targeted
How might penetration of membranes or barriers occur?
- simple diffusion
- facilitated diffusion
- active transport
- aqueous pores
- intercellular junctions
How do lipid soluble drugs pass through membranes?
simple diffusion
How do low MW, water soluble drugs pass through membranes?
- diffusion through aqueous channel
- carrier mediated transport (including passive and active)
