A drug is a chemical substance that is intended to be used in the
treatment, cure, prevention, or diagnosis of disease or used to
otherwise enhance physical or mental well-being. The use of drugs
by humans is as old as the history of humanity itself. Antibiotics are
widely used nowadays. An antibiotic can be defined as a substance
that destroys or inhibits the growth of other microorganism and is
used in the treatment of external or internal infections. The major
types of antibiotics that are commonly used include beta lactams,
cephalosporins, aminoglycosides, macrolides, carbapenems,
quinolones, tetracyclines and polymyxins.