Are there medications or other things besides alcohol that will dangerously increase the effects of xanax (alprazolam)?

Yes. Any medication or drug that sedates you, will combine with the sedating effects of xanax (alprazolam). This would include all sleeping medications, antipsychotics, other benzodiazepines, many antidepressants, etc. Xanax (alprazolam) is also metabolized by certain liver enzyme systems which can be impacted by other drugs and grapefruit juice. Drugs that inhibit these enzymes can increase effects of xanax (alprazolam).