Excretion Flashcards
Routes of drug excretion
Renal Hepatic Other
Important processes of renal excretion to pharmacology
Glomerular Filtration
Active Tubular Secretion
Tubular Reabsorption
Glomerular filtration is an (active/passive) process
Passive
Glomerular filtration rate (GFR) depends on
arterial blood pressure and renal blood flow
Factors that affect glomerular filtration
GFR
Molecular size
Electric charge
Plasma protein binding
Freely Filtered
Molecules charged or uncharged that are able to pass through the membrane freely
Active tubular secretion occurs at the
Proximal convoluted tubule
Organic Cation Transporters (OCTs)
In the proximal tubule, responsible for secretion of organic bases
Endogenous Substances and Drugs secreted by organic cation transporters (OCTs)
Endogenous : Choline, Dopamine
Drugs: Cimetidine, Procainamide, Nicotine
Organic Anion Transporters (OATs)
Proximal tubule transporter responsible for secretion of organic acids
Endogenous Substances and Drugs secreted by organic anion transporters (OAT)
Endogenous : Uric acid
Drugs: penicillin, thaizide diuretics, loop diuretics
Tubular reabsorption occurs in
Proximal and distal convoluted tubules
Tubular reabsorption is (active/passive) in the distal tubule
Passive
Acidification
Ammonium chloride / Methionine - enhances excretion of weak basic drugs
Alkalinization
Sodium bicarbonate - enhances excretion of weak acidic drugs
Factors the affect renal excretion
Age
Heart/Liver/Kidney disease
Size of drug
Protein binding
Dose-drug concentration
Lipid solubility
pKa of drug
Total renal excretion of a drug =
Filtration Rate + Secretion + Reabsorption
Hepatic drug excretion
Active transport of parent drugs and/or conjugates from hepatic sinusoids to bile canaliculi
Types of drugs likely excreted in bile
Lipid soluble with MW >300 with polar group Steroid hormones
Enterohepatic Circulation
Conjugates excreted in bile can be hydrolyzed in the intestine and the free drug can be reabsorbed
Enterohepatic Circulation allows the drug
to remain in the body for longer
Other routes of excretion
Feces
Milk/Eggs
Expired Air
Sweat
Saliva
Hair/Feathers
Excretion
Removal of the drug and metabolites out of the body
