Drug Movement Flashcards
how does the bulk flow of a drug travel in the body?
via the circulatory system
how do drug molecules travel over short distances?
via diffusionn
which type of drugs are more likely to diffuse across lipid bilayer membranes?
lipid soluble drugs
which moves quicker - large or small drug molecules?
small
name four ways by which small molecules can cross cell membranes
passive diffusion
facilitated diffusion
active transport
endocytosis
how do small molecules cross membranes via passive diffusion?
either directly through the lipid or through pores
how do small molecules cross membranes via facilitated diffusion?
via specialised carrier proteins that bind the drug on one side of the membrane, change shape and release it on the other side
does diffusion (passive or facilitated) require energy?
no
does require a concentration gradient
how do small molecules cross membranes via active transport?
via specialised carrier proteins
requires energy
how can water soluble drugs enter cells?
via facilitated diffusion or active transport, requires specialised carrier proteins
what is another name for endocytosis?
pinocytosis
how does endocytosis work?
invagination of the drug in part of the membrane to form a small vesicle, which is then released inside the cell
what is pKa?
the pH at which 50% of a drug is ionised and 50% isnt
what equation can be used to determine proportions of ionised and unionised drugs in a given pH environment?
henderson hasselbach equation
where are drugs that are weak acids absorbed?
stomach due to its low pH
where are drugs that are weak bases absorbed?
intestines due to their higher pH
what body compartment are small water soluble molecules located in?
total body water
what body compartment are large water soluble molecules located in?
extracellular water
what body compartment are large molecules and highly charged located in?
blood plasma
what body compartment are highly lipid soluble soluble molecules located in?
adipose tissue
what is the apparent volume of distribution (Vd)?
the extent to which a drug partitions between the plasma and tissue compartments
how do you calculate Vd?
dose/[drug]plasma
which drug requires a higher dose - one with a high Vd or one with a low Vd?
high = higher dose required of equal potency to show effect
what is the most abundant plasma protein?
albumin
what effect does plasma protein binding have on drug movement?
reduces availability of the drug for diffusion to the drug target organ
