My Dr Prescribed Me 25mg Hydroxyzine HCL Tablets In Place

My Dr prescribed me 25mg Hydroxyzine HCL tablets in place of the valium I take for panic attacks. But when I picked up the meds today the label says "take every 6 hours as needed for itching" and to take it every 6 hours. But I only need it in case of a panic attack. Can you tell me if I just take one tablet when an attack comes on as I would the previous medication? Thanks