Ionization of Drugs - Exam 3 Flashcards
membranes are more permeable to
non-ionized forms of drugs (lipid soluble, no electric charge)
ionization depends on
weak acid or weak base, pKa of drug, pH of medium on either side of the membrane
pKa =
pH of drug where 50% ionized & 50% non-ionized
passive diffusion with pKa, weak acid will be
high “high on acid”, curve starts at low % ionization, then with increasing pH goes high
passive diffusion with pKa, weak base will be
low “drop that base”, curve starts at high % ionization, then with increasing pH goes low
Henderson Hasselbach Equation used to
determine degree of ionization of the drug based on the pH of the environment
pKa of acid =
pH of medium + log N/I
pKa of base =
pH of medium + log I/N
if a drug is basic give it
injectable
if a drug is acidic give it
oral
antilog 1
10
antilog 2
100
antilog 3
1000
antilog -1
0.1
antilog -2
0.01
antilog -3
0.001
if pH = pKa then…
50% ionized & 50% nonionized
quarternary nitrogen compounds
mostly ionized so majority of it is excreted without being absorbed by the body; i.e.: Tubocurarine
weak acids are more ionized in what medium
alkaline
weak bases are more ionized in what medium
acidic
acids are more absorbed in what environments
acidic
bases are more absorbed in what environments
basic
what drug is basic (enhance excretion of acids)
sodium bicarbonate or anything ending in -ine
what drug is acidic (enhance excretion of bases)
ammonium chloride or methionine
