Colonoscopy allergy mystery

In June, I posted about being sent for drug allergy testing to see if I could use anti-inflammatory painkillers that I’ve had allergic reactions to before.

I went for the testing about a month ago. First off, the doctors at the drug testing centre did not want to test me for allergies to NSAIDs because I had reacted to them several times. The last time I was exposed to any was over 20 years ago, but because I had reacted to several different drugs in this class, they were pretty sure that the allergy is real. Allergies to these drugs tend not to go away over time, so testing me for them would be too risky.

Instead, I was tested to see whether I was allergic to two different medications given to me during a colonoscopy 11 years ago. I came to from that colonoscopy to realize that I was scratching my arms. I kept trying to call the nurse, saying “I’m having an allergic reaction!” over and over, but people coming out of anaesthesia often say crazy things, so she didn’t pay attention. Finally, when the nurse came over, she saw that my arms were covered in hives. I ended up being treated with a high dose of Benadryl and waking up about 8 hours later. (In retrospect, I think that the remaining anaesthetic and Benadryl in my system must have been more powerful together, because even high doses of Benadryl usually don’t keep me completely knocked out for that long).

The medications I had been given, fentanyl (an opioid analgesic) and midazolam (the actual anaesthetic) is the most common combo used for colonoscopies. Apparently they have fewer side effects and are safer to use than the older drugs. For the next decade, every time I had a colonoscopy I had to arrange in advance to have valium or demerol instead, and it kept getting harder and harder over time because hardly any hospital stocks them anymore, the older anesthetists familiar with using them are retiring, and the younger ones don’t feel confident in using them.

Even though my allergies to fentanyl and midazolam were noted in my chart, and even though I called the clinic in the weeks and days before my last colonoscopy to request valium or demerol because of the allergies, there was still somehow enough of a miscommunication at my last colonoscopy such that the drugs I knew I was safe with weren’t on hand. The anesthetist ended up proposing to “experiment” with something else, and I agreed — it’s no fun going through prep more times than necessary! I had understood — correctly — that the anesthetist wanted to try using a drug he was familiar with but that isn’t normally used during colonoscopies. The drug worked, but, seriously, most other patients would probably be horrified to hear those words when they’re lying on the gurney, ready to undergo a procedure.

Anyway, I’ve had many allergy tests in my life but the one I had to fentanyl and midazolam and latex (just in case!) were all negative. It was the most anticlimactic allergy test I’ve ever had, and it was great to know that there’s one less thing for me to worry about the next time I have to have a colonoscopy!

On the down side, it does mean that I reacted to something else during that colonoscopy 11 years ago, something that we still haven’t identified. I have a good idea of what it might have been, and I’ll still have to talk to my GI about my suspicions before I have the next colonoscopy. But at least it should make arranging things less of a nightmare next time.

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