Drug disposition Flashcards
What is in a medicine?
active drug
excipients (inactive part of drug)
What impacts can excipients cause?
bioavailability
duration of therapeutic effect
What happens to oral drugs?
tablets> granules> fine particles > solution> absorption
Site of absorption of drugs?
stomach
small intestines
Required property of drug?
It has to be lipid soluble
Absoption mechanisms of drugs?
passive diffusion
through aquaporins
facilitated diffusion
endocytosis
What is facilitated diffusion?
Selective passage of substance down its concentration
gradient via protein channel
No ATP use
can be inhibited by antagonists
What is active transport?
Movement of substance against its concentration gradient
ATP use
What is drug distribution?
The distribution of drugs via blood stream into various body tissues
What is the blood flow to liver?
680 mL/min/kg
Blood flow to kidney
3333 mL/min/kg
blood flow to CNS
615 mL/min/kg
blood flow to myocardium
833 mL/min/kg
blood flow to fat
25mL/min/kg
blood flow to muscles and others
25mL/min/kg
What is protein binding?
Binding of drug onto plasma proteins > only unbounded drugs can diffuse through membranes
What is drug metabolism?
Enzyme mediated conversion of lipid soluble compound into water soluble compound
Where does drug metabolism mostly occur?
Liver
Other places for drug metabolism to occur?
kidney, GI tract, brain, lung, plasma
What is phase I of drug metabolism?
Modification of drug structure to make them more water soluble and can cause drug to become more reactive than parent drug (pharmacological activation)
What is phase II of drug metabolism?
It conjugates drugs to large molecules e.g. amino acids, sulphate groups, glucuronic acid
it causes pharmacological inactivation
What is pharmacological inactivation?
The modification of drug structure which makes decreases receptor affinity and enhances excretion
What can happen to drug metabolising enzymes?
they can be induced or inhibited
What is drug excretion?
the removal of drug from the body via urine, faeces, lungs or skin
What is drug half-life?
the time taken for amount of drug in body to decrease to half
What is the importance of drug half-life?
Prevents drug interaction via allowing you know when one drug has be eliminated from body
important to determine how long a toxic concentration of drug will take to be decrease
What is drug therapeutic window?
The range of drug dosage from minimum therapeutic concentration to minimum toxic concetration
Consequences of renal and hepatic diseases on drugs?
Drug concentrations may reach toxic levels due to elongated half life time
