Part a Pharmacokinetic processes u Simple diffusion A Weak acid B Weak base Lipid Lipid membrane membrane BH BH B HA Bod Bod Bod Bod compartment compartment compartment compartment
Simple diffusion Part A Pharmacokinetic Processes
Part a Pharmacokinetic processes D Determinants of simple diffusion For most drugs of small molecules(usually are weak acids or weak bases) o Lipid-soluble or un-ionized forms o pKa of the drug and pH of the body fluid I The pKa is that pH at which the concentrations of the ionized and un-ionized forms are equal
Determinants of simple diffusion For most drugs of small molecules (usually are weak acids or weak bases): Lipid-soluble or un-ionized forms pKa of the drug and pH of the body fluid The pKa is that pH at which the concentrations of the ionized and un-ionized forms are equal. Part A Pharmacokinetic Processes
Part a Pharmacokinetic processes D Henderson-Hasselbalch equation o Weak acid drugs: PH-pKa=log(A|/[HAD pKa-PH=log (HA/A)) D Weak base drugs pKa-PH=log(()/(B)) PH- pKa=log([B/BHD)
Henderson-Hasselbalch equation Weak acid drugs: pH - pKa = log ( [A- ] / [HA] ) pKa - pH = log ( [HA] / [A- ] ) Weak base drugs: pKa - pH = log ( [BH+ ] / [B] ) pH - pKa = log ( [B] / [BH+ ] ) Part A Pharmacokinetic Processes
Part a Pharmacokinetic processes un-ionized lipid- Simple pH pKa form soluble diffusion Weak 1 And/or I aids△ad/rt Weak f LAnd /or E>1 b ases And /or I
Part A Pharmacokinetic Processes pH pKa un-ionized form lipidsoluble Simple diffusion Weak acids Weak bases And / or And / or And / or And / or
H=7 Membrane PH=4 A+H=HA HA =H+A (10) (10) 7=8+log X) 10 4=8+ log N0 olving: Solving ×) 10-1 10 n=10-4 )=1 )=0.001 I part in 11 ionized (9%) 0.001 part in 10.001 ionized 001%