Phenobarbitol is the go to drug in the animal world to help prevent seizures. It is a barbiturate. Here is what Mayo clinic says about barbiturates.
Barbiturate (Oral Route, Parenteral Route, Rectal Route) - Drugs and Supplements - Mayo Clinic
They are a central nervous system depressant and as such Hank couldn't have them when he started having seizures a few weeks before he died. If your bird has cardio/pulmonary issues, like Hank did, you can imagine that nothing the suppresses the central nervous system is safe. As it turned out Hank's seizures were caused by low blood sugar and were simple to control once we found that out. My vet allowed me to keep a couple of injections of Valium on hand to stop severe seizures, but I never had to use them.
Jasper was on Haloperidol to control her chewing on her foot when she lost half of one toe. It was difficult to find the correct dosage and she ranged from zombie bird with too much, to freaky bird when coming down off of it. It did the job and she quit messing with her toe stump, but was nerve wracking while she was on it.
Jasper has been on DMG for over a year with no adverse side effects, but she is taking it for general health purposes.