I have severe panic attacks my last doctor had me on 4mg tid 12mg a day, my new dr cut it half that what is the highest dosage that is safe?

Which medicine?: It's not clear from your question what medication you're asking about -- but if xanax (alprazolam), (alprazolam) 12mg/day is a very high dosage. Such a dose of xanax (alprazolam) would indicate tolerance, and your doctor would need to see whether this is helping your symptoms at all. There are safer medications than xanax (alprazolam) for long-term use in panic disorder. Hoping your dose was tapered, not just cut in half.

XANAX (alprazolam) DOSAGE: The maximum recommended dosage for xanax (alprazolam) is 3 mg three times a day. Please be aware that xanax (alprazolam), like all other sedative drugs in the benzodiazapine drug class, can be both psychologically and physically addictive. Use the lowest effective dose and for as short a time as possible. Since you also take the sedative ambien, use with caution as the combination poses a risk of CNS depression.