I have a prescription to hydroxyzine hcl to take as needed for anxiety. Its effects on my anxiety are minimal, but that may be because I've taken a good amount of xanax over the years, which I've found completely blows all other anxiety meds out of the water. However, I can greatly potentiate the effects of an opiate if I take 25-50mg of hydroxyzine about 30-45 minutes before dosing any opiate. If nausea/itching are common/undesirable when using opiates, hydroxyzine also helps with these. It can make the effects of more stimulating opiates (oxycodone in particular from my experience) more sedative in nature if I'm looking for a nod and don't have access to a more sedating opiate.
Just be careful about how much hydroxyzine you take and how often you dose; it is a powerful antihistamine and I once suffered from drug-induced delirium from taking too much in a day (some people enjoy "tripping" on benadryl, I don't).