Medication allergies

Just about all medications cause side effects of one kind or other.  Sometimes they're not unpleasant, and some can actually be helpful.  Other times they're harmful or even deadly.  Patients tend to classify all unpleasant medication side effects as "allergies."

Most adverse reactions aren't true allergies, though.  For example, I know from experience* that morphine makes me vomit.  A lot.  That doesn't mean I'm allergic to morphine.  On the contrary, nausea is a known side effect of many narcotics (morphine and closely related drugs).  It can usually be controlled with medications.  But most patients who get nauseated from one narcotic or other will say they're allergic to that drug.  There are plenty of other medication "allergies" that doctors hear very commonly.

Examples:

- "I'm allergic to lidocaine!  The dentist injected it and my heart started racing!"  (Dentists use lidocaine mixed with dilute epinephrine.  If it gets injected into one of the copious tiny blood vessels in the mouth, the epinephrine causes an increased heart rate that can tell the dentist that the injection is intravascular.  This is a normal reaction; it means the epinephrine is doing what it's supposed to do.)

- "I'm allergic to (enter antibiotic here)!  It gives me diarrhea!"  (Actually, antibiotics often kill the good bacteria in our bowels as well as the bad ones that make us ill.  The absence of the normal gut bacteria leads to diarrhea.)

- "I'm allergic to (enter narcotic here)!  It made me really constipated!"  (That's another normal side effect of narcotics, just like nausea.  They stop stuff from coming out down below and make it come out up above.)

- "I'm allergic to (pick a drug, any drug)!  It didn't work!"  (Not sure I need to actually explain why this isn't a real allergy.)

Generally, doctors don't correct patients when they incorrectly claim to be allergic to medications.  If a patient specifies symptoms that are unpleasant but are not true allergies, we note the drug and the reaction and move on.  There are usually alternatives that prevent us from having to give patients the medications they dislike.  And if it's unclear whether a patient truly has an allergy to a medication, we would always prefer to err on the side of patient safety.  After all, some non-allergy adverse reactions can actually be life-threatening themselves.

As a fourth-year med student, I was on an anesthesiology rotation in a city hospital.  I had recently decided to pursue a career in anesthesiology and was excited to be on the rotation.  On this particular day, I was evaluating a pleasant middle-aged woman together with my attending.  I no longer recall what procedure she was having done, but I do remember the patient clearly.  She was an obese black woman from the inner city who looked like she would be right at home in a gospel church choir.  She was a sweet lady and my attending and I both liked her immediately.

"You're wearing an allergy band, Ms. Jones.  What medications are you allergic to?" I asked.

"I'm allergic to penicillin and lisinopril," she replied.

"What happens when you get penicillin?"

"Oh, I get a terrible rash and hives all over my body!"

"Mm-hm," I said, making a note.  "And what about lisinopril?"

I expected my patient to reply that lisinopril gave her a dry cough, a common side effect that isn't harmful but can be so irritating to people that they stop taking the drug.  But lisinopril hadn't made this patient cough.  With a look of horror on her face, my patient exclaimed, "It was so bad!  I got all swelled up like a mongoloid!"

Angioedema is a rare but potentially life-threatening side effect of lisinopril.  Further inquiry in the patient's medical record showed that she had, in fact, developed angioedema a few years earlier and had required intubation and ICU management.

My attending thought her description of the lisinopril event was hilarious.  For the rest of the day (and a couple days afterward), he could be heard in the hallways of the OR suite singing the lyrics from Devo's song.

*No, I haven't been naughty.  A doctor gave me IV morphine in the ER several years ago, before I'd even started med school.