THERAPEUTICS Flashcards
what is pharmacodynamics?
what the drug does to the body
what is pharmacokinetics?
what the body does to the drug
what is a medicinal product?
a substance or combination presented as having properties for treating or preventing disease in human beings eg drugs
what is a medical device?
anything as simple as a plaster all the way to an MRI machine (any instrument/ machine/ apparatus)
what are the 2 methods by which drugs enter the system?
- Active transport
- Passive diffusion
what 4 processes does pharmacokinetics involve?
- absorption
- distribution
- metabolism
- excretion
where is the main site of metabolism in pharmacokinetics?
liver
where is the main site of excretion in pharmacokinetics?
kidneys
what is a formulation?
the pharmaceutical form of a drug eg tablet or capsule
what does liberation mean?
the release of a drug from its pharmaceutical form
what is drug absorption?
drug being moved into systemic circulation after being administered
what is distribution?
movement of drug into tissue from systemic circulation
what is drug metabolism?
conversion of drug into other chemicals in the body
what is drug excretion?
elimination of medicine from the body
what is the formula for calculating the volume of distribution?
vol of distribution = dose/ plasma conc
what does lower vol of dist (Vd) mean?
drug stays in blood stream
eg warfarin
what does higher vol of distribution mean?
drug moves into tissues
eg propranolol
what is therapeutic index?
the ratio of the dose that results in an undesired effect to that which results in a desired effect
what does therapeutic drug monitoring involve?
clinical practice of measuring specific drugs at designated intervals to maintain a constant concentration in a patients bloodstream, thereby optimising individual dose regimens
name some drugs with a narrow therapeutic index
- aminoglycosides
- ciclosporin
- carbamazepine
- digoxin
- flecainide
- lithium
- pheytoin
- rifampicin
- theophylline
- warfarin
what are some factors affecting drug absorption (5)?
- formulation
- motility of the gut
- food in stomach
- degree of 1st pass metabolism
- lipid solubility
what are some factors affecting drug distribution (4)?
- lipid solubility
- degree of ionisation
- drugs which are highly protein bound
- pharmacogenetics
what is the only type of drug that can exert an effect?
unbound drugs
what is a ‘free drug’?
active drug
which fruit acts as an enzyme inhibitor?
grapefruit
what is meant by affinity?
how actively the drug binds to the receptor
what is meant by efficacy?
ability of drug to elicit a response when it binds to the receptor
what is meant by potency?
a measure of the amount of drug required to produce an effect
what is an agonist?
drug that activates a receptor
what is an antagonist?
a drug which blocks a receptor
what is a partial agonist?
drug that binds to and activates a given receptor, but only has partial efficacy at the receptor (relative to full agonist)
describe competitive inhibition
- this blocks an enzyme at its active site
- it is temporary
describe non-competitive inhibition
this stops an enzyme from working by changing the shape of the active site by combining to the allosteric site (not active site)
what is bioavailability?
the proportion of the administered drug that reaches the systemic circulation, must first pass the intestinal wall and the portal circulation to the liver
what does the area under the bioavailability curve indicate?
the extent of the absorption
what is the peak concentration of the bioavailability curve?
the highest conc of a drug in the plasma after a dose is given
what is the median toxic dose?
the dose at which toxicity occurs in 50% cases in the population
what does a phase 1 metabolic reaction primarily involve?
oxidation
what does a phase 2 metabolic reaction primarily involve?
conjugation
describe characteristics of phase 1 metabolic reactions
- involves a biotransformation of a drug to a more polar metabolite
- involve CYP enzymes
- these reactions mostly oxidation but can be reduction or hydrolysis
what happens to phase 1 product in phase 2 metabolic reaction?
phase 1 product is bound to conjugate
-drug is now more hydrophilic
what is drug clearance?
the volume of fluid cleared of a drug per unit time
what is half-life?
the time for the plasma concentration to fall by 50% of what it was at equilibrium
what is distribution half-life?
when plasma levels fall to half what they were due to distribution of the drug to body tissue
what is elimination half-life?
when plasma levels fall to half of what they were due to the drug being metabolised and eliminated
what is 1st order elimination?
rate of drug elimination is dependent on plasma conc
what is zero order elimination?
rate of elimination is constant and independent of plasma conc
how does the elimination half-life relate to the time taken for drug to be eliminated from the body ?
x5 elimination = time at which the drug is eliminated
what are the 5 classes of drugs?
- beta-blockers
- ACE inhibitors
- ARBs (angioptensin 2 receptor blockers)
- cholesterol-lowering drugs
- calcium channel blockers
what do beta-clockers generally end in?
-alol or -lol
what do beta-blockers do?
block the beta-adrenergic receptors—->blocks the sympathetic nervous system to heart and lungs, primarily slows heart rate, reduces BP
what are some common side effects of beta-blockers (4)?
- bradycardia
- hypotension
- congestive heart failure (if HR too low)
- bronchospasm
what do ACE inhibitors typically end in?
-pril
what do ACE inhibitors do?
inhibit angiotensin converting enzymes in the lungs (ACE) —->lower BP
what are some common side effects of ACE inhibitors (3)?
- chronic cough
- angioedema
- hypotension
what do ARB’s (angiotensin II receptor blockers) typically end in?
-sartan
what do ARBs do?
block angiotensin II-which is vasoconstrictor–>lower BP
what do cholesterol-lowering drugs generally end in?
-statin
what do cholesterol-lowering drugs do?
inhibit fat adsorption and inhibit cholesterol production
what are some common side effects of cholesterol-lowering drugs (4)?
- steatorrhoea
- muscle weakness
- diarrhoea
- abdominal discomfort
what do calcium channel blockers generally end in?
-pine
what do calcium channel blockers do?
block calcium channels
what are some common side effects of calcium channel blockers (3)?
- bradycardia
- hypotension
- heart failure
what is meant by ED50?
-dose of medicine that produces desired pharmacological effect in 50% of the studied patient population that takes the medication
what is meant by TD50?
-median toxic dose of drug/toxin-toxicity occurs in 50% cases
What is better a small or large therapeutic index?
Large
What is an example of a drug with a large therapeutic index?
Paracetamol
