Does vistaril enhance the effects of oxycodone?
Yes. First generation antihistamines (i.e. Vistaril, Benadryl)
increase the analgesic effects of most opiates so that a lower dose
of opiate can be given. Antihistamines also reduce some of the side
effects, such as itching and nausea. Vistaril can also inhibit the
enzyme that metabolizes Oxycodone, but I think that is negligible
unless the Vistaril dose is very high (over 100mg).