Drugs Acting on the Central Nervous System Definition, classification, pharmacological actions, dose, indications, and contraindications of General anaesthetics

**General anaesthetics** are drugs that produce a reversible state of unconsciousness, analgesia, amnesia, and muscle relaxation, allowing painless surgical procedures. They act primarily on the central nervous system by enhancing inhibitory neurotransmission (mainly via GABA receptors) and/or inhibiting excitatory pathways. General anaesthetics may be administered by inhalation (e.g., volatile agents and gases) or intravenously. These agents depress cerebral activity, suppress reflex responses, and alter autonomic functions in a dose-dependent manner. Modern general anaesthesia aims to achieve adequate depth of anaesthesia with rapid onset, smooth maintenance, and quick recovery while minimizing adverse cardiovascular and respiratory effects.