Most of the drugs are excreted in -
Ans. is 'b' i.e., Urine o Most important channel of excretion for most drugs is through kidney (in urine).EXCRETION OF DRUGSo Drugs and their metabolites are excreted in :Urineo Through the kidneyo It is the most important channel of excretion for most drugs.o Net renal excretion = (Glomerular filtration + tubular secretion) - Tubular reabsorption,o Glomerular filtrationDepends on plasma protein binding and renal blood flow.Does not depend on lipid solubility.o Tubular reabsorptionDepends on lipid solubilityMore lipid soluble drugs are absorbed more and less excreted.Ionized drugs, being less lipid soluble, are more excreted.Acidic drugs (salicylates, barbiturates) are more ionized at alkaline pH. So urine should be alkalinized in poisoning of these drugs.Similarly, urine should be acidified in poisoning of basic drugs (morphine).o Tubular secretionDoes not depend on plasma protein binding or lipid solubility.This is active transport of organic acid and bases by two separate classes of relatively nonspecific transporters (OATand OCT).In addition, efflux transporters P-gp and MRP2 are located in the luminal membrane of proximal tubular cells.Organic acid transport (through OAT) for Penicillin, Probenecid, uric acid, salicylates and sulfinpyrazone.Organic base transport (through OCT) for diuretics (thiazide, amiloride, furosamide, triameterene), quinine and procainamide.Both transport processes are bidirectional, for drugs, secretion into the tubular lumen predominates, whereas an endogenous substrate like uric acid is predominantly reabsorbed.Faeceso Drugs present in the faeces are derived from unabsorbed fraction plus actively secreted into bile,o Drugs that attain high concentration in bile are -* Erythromycin# Oral contraceptives# Rifampin* Ampicillin# Tetracycline# PhenolphthaleinExhaled airo Gases and volatile liquids are eliminated by lungs.Saliva and sweato These are of minor importance.o Lithium, Pot. iodide and rifampin are present in these secretions.5. Milko Most drugs enter breast milk by passive diffusion,o Lipid soluble and less protein bound drugs cross better.
Faeces
Urine
Saliva
None
Pharmacokinetics