Ionization

Question 1

pKa

Answer 1

ionization constant of a chemical compound - it is the pH at which the drug will exist in solution as 50% ionized and 50% non-ionized

All drugs are salts of a weak acid or base

Question 2

Not question/answer set up - just listing the steps for determining ionization:

STEP 1:
If pH - pka = 0 then the ratio is 50/50%
If pH - pka = 0.5 (absolute value) then ratio is 75/25%
If pH - pka = 1 (absolute value) then ratio is 99/1%

Answer 2

Determining what percentage is ionized or non-ionized:

STEP 2:
acids in acidic pH = non-ionized/lipid soluble
bases in basic pH = non-ionized/lipid soluble
acids in basic pH = ionized/water soluble
bases in acidic pH = ionized/water soluble

LIPID SOLUBLE/NON-IONIZED DRUGS WILL CROSS MEMBRANES/DIFFUSE

Question 3

pH of body fluids

Answer 3

Gastric juices 1-3.0
Blood 7.4
CSF 7.3
Intestine 5-8.0 (depending on where) 
Urine 4-8.0