目b. Facilitated diffusion(易化扩散) o(transporter-mediated diffusion) ccarriers D. endocytosis transporters) exocytosis into or out of o Involving specific carriers(transporter) cells o Energy-independent o Saturability o Competition with other drugs o Concentration gradient(down-hill) 口(3) Endocytosis/ exocytosis(入胞/出胞)
b. Facilitated diffusion（易化扩散） (transporter-mediated diffusion) Involving specific carriers (transporter) Energy-independent Saturability Competition with other drugs Concentration gradient(down-hill) (3) Endocytosis/exocytosis（入胞/出胞）
口 Another classification u Passive transport Simple diffusion(简单扩散/单纯扩散 口 Filtration(滤过) 口 Facilitated diffusion(易化扩散) 口 Active transport 口 Active transport(主动转运) Pinocytosis/exocytosis(入胞/出胞)
Another classification Passive transport Simple diffusion（简单扩散/单纯扩散） Filtration（滤过） Facilitated diffusion（易化扩散） Active transport Active transport (主动转运) Pinocytosis/exocytosis（入胞/出胞）
口A. Simple diffusion Most drugs are weak acids or bases Weak acid Their diffusion Weak base passing through cell Lipid membrane depen ds Lipid membrane membrane the lipid-soluble state BH (un-ionized form) HA B A HA Body Bod Body Bod compartment compartmen compartment compartment
A . Simple diffusion Most drugs are weak acids or bases. Their diffusion passing through cell membrane depends the lipid -soluble state (un -ionized form)
u 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 u The pKa is the 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 the pH at which the concentrations of the ionized and un-ionized forms are equal
o Henderson-Hasselbalch equation Weak acid drugs: PH-pKa=log(a/Had pKa-pH=log(田HA/[A1) Weak base drugs pKa-PH=log( bh|/BD) PH-pKa= log(b/BiD)
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+ ] )