drug administration and elimination Flashcards
name some methods of administering drugs and their time to effect
Intravenous
30-60 seconds
Inhalation
2-3 minutes
Sublingual
3-5 minutes
Rectal
5-30 minutes
Intramuscular / subcutaneous
10-20 minutes
Oral
30-90 minutes
what is the name of the cytochrome that partially metabolises drugs in the gut epithelium
CYP450 3A4
what else partially metabolises drugs in teh GI tract
gut bacteria
what is bioavailability
how much drug is available to be used systemically
what is the BA of IV administered drugs
100%
where is most BA lost in orally administered drugs
liver
what is a prodrug
inactive drug that is metabolised to its active state
what is L-Dopa
pro drug of dopamine
how can prodrugs be used in cancer
antibody, gene or virus (ADEPT, GDEPT, VDEPT) delivered to cell. DNA expresses an enzyme
prodrug is administered
enzyme metabolises that cytotoxic drug and it sends the cells to apoptosis.
Bystander effect - nearby cells are also killed
a patient has an adenocarcinoma of the lung. what is the most likely mutation
EGFR overexpression
how would you use a prodrug to prevent tumour growth but not affect surrounding tissue
prodrug only binds to hypoxic tumour tissue
which enzymes catalyse phase 1 of liver metabolism
CYP450
what happens in phase 1
Oxidation
Reduction
Hydrolysis
why would a molecule go to phase 2
too lipophilic
what is the main mechanism in phase 2 and which molecule does it
glutathione conjugation - glutatione S-transferases
why are adjuncts added to molecules in phase 2
to make them more polar = soluble
what is carbemazepine
a CYP450 inducer epileptic drug
which enzymes carry out oxidation, reduction, hydrolysis, conjugation, acetylation
O: CYP450 monooxygenazes
R: aldehyde and ketone reductases
H: esterases and amidases
C: gluathione S-transferases
Sulphotransferases
A: N-acetyl-transferase
polar metabolites go to
non-polar metabolites go to
kidneys - wee
liver/GI - poooooooo
how do you calculate clearance?
amount of drug lost in urine per hour/amount of drug remaining in plasma
how do you calculate a half life
t1/2=(Vd/Cl) x 0.7
for first order drugs, what should the dosing interval be
around 4(t1/2)
what is the therapeutic window
a timeframe during which a drug is effective in the range between MEC and MSC
what is succinylcholine used for
skeletal muscle paralysis during anaesthesia
