Hydroxyzine dihydrochloride inhibits carbachol (10 μM)-induced serotonin release by 34% at 10 μM, by 25% 1 μM and by 17% 0.1 μM in pretreated bladder slices for 60 min.

Hydroxyzine dihydrochloride (12.5 mg/kg, 25 mg/kg and 50 mg/kg i.p.) shows little direct analgesic activity but markedly potentiates only the effect of morphine on the vocalization after-discharge which represents the affective component of pain in rats. Hydroxyzine dihydrochloride (50 mg/kg i.p.) potentiates morphine on the tail-flick test, while Hydroxyzine (12.5 mg/kg i.p.) decreases morphine antinociception in rats.