Don't worry- it's administered at an IV day hospital where the folks are specially trained, and they aren't allowed to administer it unless there is a gastro on premises (at least here)
They have emergency benedryl IV on hand in case something happens. Reactions are not unheard of so they will take precaustions.
Also I would tell them of your family history with the drug and your apprehension..they will monitor you closely.
33 years old, dx with Crohn's in 1998. Currently on :
Clofazimine 100mg daily,
Rifampin 600mg daily, and Clarithromycin 2 tabs daily
and Cipralex 10mg/day for anxiety.
Hydroxyzine, percocet, Ativan as needed.
5g pharmaceutical grade Omega 3's, 1000IU's Vitamin D3 daily
2 Perianal fistulas, and 1 more suspected. Crohn's only at end of colon, cecum. Remi, Asacol, Salofalk, Imuran, Humira did nada. Built immunity to long-term Cipro use, which also induced panic attacks.