Aside from benzodiazepines, are there any equally effective treatments to prevent severe panic attacks?

Yes, you can see: A clinical psychologist and learn some techniques to help you deal w/them. If your doc has ruled out medical conditions there are strategies you can learn to manage them. Fear of having a panic attack becomes the main issue and that may be the case w/you. They are self-limiting. Peace and good health.

Yes: Other pharmacological options include antidepressants such as ssri's, some tricyclics, and maoi's. A psychiatrist can evaluate your situation and recommend effective treatments. Because they induce tolerance, benozdiazepines are not a good long term approach. Paired with antidepressants, various types of psychotherapy (including cognitive behavioral) are essential and will improve your results.