Tranquilizers can be divided into two groups: major tranquilizers and minor tranquilizers.
Minor tranquilizers decrease anxiety as well as induce sleep and may also act as a general anesthetic.
Major tranquilizers include phenothiazines, indoles, thioxanthenes, butyrophenones, piperazine compounds and piperidine compounds.
These drugs are referred to as neuroleptics and are most commonly prescribed as anti-psychotics. Both azaperone and promazine belong to the group of major tranquilizers.
Besides tranquilizers, β-adrenergic receptor blocking agents can be used for the prevention of transport illness, stress syndrome and meat alterations in pigs. Carazolol, a structural analoque of the catecholamines adrenaline and noradrenaline, belongs to this group.