Tranquilizers are basically drugs which are used for treatment of anxiety, tension, fear or any disturbance of mind and helps in sleeping. It is therefore an antidepressant as it helps in restoring the balance of neurotransmitters in our brain. E.g. Phenelzine (C₈H₁₂N₂) or Nardil.

Noradrenaline is an organic chemical in the catecholamine family that functions in the brain and body as a hormone and neurotransmitter and tranquilisers function by inhibiting the enzymes which catalyse the degradation of noradrenaline. So, it relieves from any anxiety, fear or tension.

So, tranquilisers are neither any type of narcotic drugs nor do they relieve pain and fever. They do not affect the message transfer from nerve to receptor.