My husband has suffered from anxiety and panic attacks for years. Many doctors told him they couldn't diagnose the problem and ended up putting him on drugs with very severe side effects. My suggestion---look for safe answers in naturopathic or holistic medicine. Do some studying and reading on the inet and you will be able to find info on what natural supplements he may be able to take to help. Of course, seeing a naturopathic doctor would be the best, but most insurance doesn't cover, so it's expensive.
He needs to have some simple tests done to see what may be out of balance in his brain chemistry, and/or other body systems that may be in need of help. You also need to learn more about what he eats and what may need to be changed in that area. Certain foods and drinks have been shown to greatly increase anxiety and panic attacks. Finally, drinking water will certainly always help. My husband has found help with an herbal medicine called Zen, unfortunately, I don't recall the company off the top of my head. If you email me at firstname.lastname@example.org, I will try to find out for you if you want.
My best advice is not to use prescription meds because of the side effects. Lots of problems there. Find out what you can to help him in a natural way as much as possible. lspryor