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ELIMINATION OF DRUGS - Coggle Diagram
ELIMINATION OF DRUGS
FACTORS AFFECTING RENAL EXCRETION
molecular size of drug
drugs mol.wt <300 = excreted in kidney
drugs mol. wt 300-500 dalton= excreted through urine and bile
binding characteristics of drug
bound to plasma proteins (has long half lives)
cannot be filtered through glomerulus
unbound/ free drug
appear in glomerular filtrate
biological factors
age, sex
drug interaction
increase or decrease
disease state urine pH
renal failure
blood flow to the kidney
OTHER ROUTES OF DRUG ELIMINATION
exhaled air
gases and volatile liquids like
-general anesthetics
-alcohol
eliminated by lungs
breast milk
lipid soluble drugs enter breast milk by passive diffusion
-serious adverse effect in infant
e.g; chloramphenicol, chloroquine
sweat, saliva, tears
saliva- rifampicin
sweat- lithium
nails
griseofulvin
hair follicles
arsenic
DRUG EXCRETION
removal of drugs from the body
most important organ: kidney
through urine, bile, sweat, saliva, breast milk, expired air
main process of renal excretion:
glomerular filtration
depends on renal blood flow
types of drugs filtered here:
smaller drugs molecules, MW < 20000
free drug (at glomerulus)
drugs that not filtered here:
drugs that bound to plasma albumin eg warfarin
after age 50, glomerular filtration declines
active tubular secretion
80% drug reaches proximal tubule
types of drugs filtered here:
protein bound drugs
use 2 independent carriers sytems (carrier mediated)
-transport agains electrochem gradient
acidic drugs
basic drugs
most effective mechanism
80% of drug delivered to kidney is excreted by carriers
most of drug are protein bound
passive tubule reabsorption
occurs at proximal tubule
drugs and endogenous share same transporter
probenecid can prolong the action of penicilin by competing for tubular secretion
diffusion across the renal tubule
occur in distal convoluted tubule
when? lipid soluble drugs are reabsorbed by passive diffusion back into the system
drugs which high polar will be retained in the tubules and excreted
e.g; aminoglycosides
ZERO ORDER AND FIRST ORDER ELIMINATION
ARTIFICIAL EXCRETION
hemodialysis
-treat acute drug intoxications to eliminate drug in body
TOTAL BODY CLEARANCE
sum of individual clearances by all eliminating organs
