DRUG EXCRETION Flashcards
Name the primary routes by which drugs are excreted from the body
Major routes:
Renal → via kidneys
Biliary → feces
Other routes:
Pulmonary
Salivary
Mammary
List the key processes Identify the key processes
Filtration
Active Tubular Secretion
Tubular Reabsorption
Biotransformation
Where does Filtration occur?
Glomerulus
Where does Active tubular secretion occur?
Proximal Tubule (PCT)
Where does tubular reabsorption occur?
Ascending Loop of Henle / DCT
Where does biotransformation occur?
the liver
Describe how the physicochemical properties of a drug influence its filtration
Determinants of glomerular filtration:
number of functional nephrons
molecular size (MW < 5000)
protein binding
renal blood flow
Describe how the physicochemical properties of a drug influence its reabsorbtion
Passive reabsorption:
Driven by conc gradient
Determined by lipophilicity & pKa of drug
Influenced by urine flow & urine pH
NOT SATUATABLE & competitive interactions between drugs
Carrier-mediated reabsorption:
Saturatable (capacity-limited)
Describe the relationship between molecular weight and renal clearance
inverse
Higher MW = Lower renal clearance
Describe the relationship between molecular weight and percent of drug excreted in bile
High MW = higher % of drug excreted in the bile
When the MW is lower, there is not significant % of the dose excreted in the bile
Describe the impact of enterohepatic recirculation on drug half-life in the body
Enterohepatic recirculation can reduce elimination of xenobiotics, prolonging the half-life
