David, just a little of what I managed to 'Google'. Not a drug I have come across before.
Pericyazine belongs to a group of medicines known as the phenothiazine antipsychotics. It is sometimes described as a 'major tranquilliser'. It acts by blocking a variety of receptors in the brain, particularly dopamine receptors. Dopamine is involved in transmitting signals between brain cells. When there is an excess amount of dopamine in the brain it causes over-stimulation of dopamine receptors. These receptors normally act to modify behaviour and over-stimulation may result in psychotic illness. Pericyazine blocks these receptors and stops them becoming over-stimulated, thereby helping to control psychotic illness.
As usual side effects listed, as with all drugs.
Trust everything is O.K. with you. Please let us know how your wife gets on with her new treatment.