Anaesthetics:- Anaesthetics may be defined as those drugs which produce insensibility to the vital functions of all types of cells especially of nervous system. The effect produced by anaesthetic is reversible, i.e., affected organs return to the normal state as soon as the concentration of the anesthetic is decreased. Thus, anaesthetic produces temporary insensibility to pain or feeling in the whole body or a particular organ. Anaesthetics may be classified into two groups on the basis of their applications.
(i)          General Anaesthetics:- These depress the central nervous system to such an extent that all sensitivity to pain or feeling is host, i.e., they produce unconsciousness all over the body. These are used for major surgical operations. These may be used in the form of gas, e.g., nitrous oxide, cyclopropane, ethylene, ether or may be given in the injection form e.g., sodium pentothal.
(ii)         Local Anaesthetic:- These affect only part of the body insensitive to pain or feeling. Common local anaesthetics are: xylocaine, ethyl chloride, and procaine. These are used for small surgical operation like tooth extraction, stitching of a wond or incision of an abscess. Some other modern local anaesthetics are,  a-eucaine, orthocain and dimethisoquin.