PHARMACOLOGY

 LUNGS ::

General anaesthetics like chloroform ether nitrous oxide etc are excreted through exhalation Certain volatile oils and drugs like paraldehyde and alcohol are also excreted through the lungs 

Gastrointestinal tract ::

An orally administered drug is excreted per rectum if unabsorbed whereas drugs from systemic circulation are also excreted through saliva bile and colon Even when administered through other channels injection of opium is excreted through the stomach Hence gastric lavage is important in all cases of opium poisoning 

                Besides gastrointestinal tract drugs are directly excreted through the large intestine Mercury and emetine are examples in point Substances like phenol-phthalein and tetracyclines which are excreted through bile are also brough out by the colon Drugs like iron senna etc are absorbed by the small intestine and again excreted through the colon 

Biliary and fecal excretion ::

Metabolites of many drugs are excreted into the intestinal tract in the bile Some metabolites are excreted into faeces Organic anions including glucuronides and organic cations are actively transported into bile by the carrier systems Steroids and related substances are transported into bile by a third carrier stem 

Excretion of drugs through milk ::

Nearly all drugs received by mother are likely to be found in her milk during breast feeding (lactation) However it may be possible that only a few drugs are found in concentration that can affect the infant adversely Examples of such drugs are benzylpenicillin erythromycin chloramphenicol sulfonamide and radioiodine 

                Milk is slightly more acidic as compared to plasma hence basic compounds can be excreted well in milk Non -electrolytes like ethanol and urea enter milk independent of its pH 

Other routes ::

Drugs are also excreted through sweat saliva and tears Elimination by these routes depend upon diffusion of non-ionized lipid soluble form of drugs