pharmacology Flashcards
what drugs decrease INR
rifampicin, carbamazepine, phenytoin, cholestyramine and st johns wort
what is a type A adverse drug reaction
can be managed somewhat by judicious prescription and awareness or influencing factors eg renal failure, drug interactio
what is a type B adverse reaction
by definition idiosyncratic, e.g. agranulocytosis with carbimazole
screening will have minimal yield
What are some drugs that display zero order kinetics
aspirin, alcohol, phenytoin, theophylline and perhexiline
the elimination of a drug remains constant regardless of the plasma concentration
With saturable metabolism, a change in dosing regumen has the capacity to cause exaggerated changes to drug levels
How do you work out drug dosing based on fraction excreted unchanged in unirine with renal function
The fraction of the original dose = (1-fu) + fu(fraction of original CrCl)
fu= fraction of drug excreted unchanged in urine
(1-0.5) +05(0.5) = 0.75 = 75%
What is pharmacokinetics?
the study of what the body does to the drug
absorption, dsitribution, metabolism and excretion
what is pharmacodynamics
the study of what the drug does to the body
What is potency?
the amount of drug required to produce an effect of given intensity
differences in drug potency are evaluated by comparing EC50
What is efficacy?
The ability of a drug to produce a maximum response
evaluated by comparing differences in maximal response at high drug doses
What will competitive inhibition lead to?
Decreased potency, curves move further away
What will non-competitive inhibition lead to?
decreased efficacy
What is bioavailability?
The fraction absorbed into the systemic circulation is the drug’s bioavailability
= AUC(po) / AUC(iv) * 100
What is volume of distribution
the volume in the bucket of water that you dump your drug dose into
What is clearance?
the volume of bucket water per unit time that is filtered completely free of drug
How do you calculate Vd?
Vd = loading dose/concentration
