Pharmacokinetics and Pharmacodynamics Flashcards
What is pharmacodynamics?
What drug does to body
What is pharmacokinetics?
What body does to drug
What are the stages of pharmacokinetics?
Liberation Absorption Distribution Metabolism/biotransformation Excretion
How is lipid solubility of a drug measured?
Partition coefficient (P) = [drug]chloroform/[drug]water
What is the equation for the dissociation of a weak acid?
HA H+ + A-
What is the equation linking pH and pKa for a weak acid?
pH - pKa = log([A-]/[HA])
What is the equation for the dissociation of a weak base?
BH+ B + H+
What is the equation linking pH and pKa for a weak base?
pH - pKA = log([B]/[BH+])
What is the meaning of pH = pKa?
50% of drug ionised
What is the key difference between gastric/intestinal administration and sublingual/rectal administration?
Gastric/intestinal drug reaches liver before blood - first pass mechanism
Sublingual/rectal drug enters blood directly
What is bioavailability (F)?
Extent of therapeutically-active drug reaching systemic circulation
What are the steps affecting bioavailability?
Incomplete drug release from formulation Enzymatic degradation in stomach Not absorbed Destroyed by gut wall Destroyed by liver - first pass metabolism
Which graph can bioavailability be determined from and how?
Plasma conc against time
Area under curve
What are the stages of drug excretion from kidney?
Glomerular filtration
Tubular secretion
Tubular reabsorption
What is first order elimination kinetics?
Drug conc decreases exponentially with time
Elimination proportional to conc
T0.5 constant
