If a pt. is allergic to codeine, can she have morphine (sulfate, PO)?

[dura.mater]

Working on prepping for my first Sim Lab and our patient is allergic to codeine but has an order for morphine sulfate, 15 or 30 mg PRN for pain. She is 85 with Hx of HTN, MI, CHF. I know codeine basically breaks down into morphine in the liver so I feel like she shouldn't have it, but the rest of the internet is giving me conflicting info. My Mosby drug book and Med Deck aren't helping. Any advice?

[MunoRN, RN]

Assuming it's a true allergy and not a fairly normal and expected side effect or pseudoallergy symptom, an opiate from the semi-synthetic family (ie hydrocodone) could be tried since there's a decent chance the patient won't be cross reactive. Full synthetics like fentanyl would have the least chance of cross reactivity with a true codeine allergy. The mechanism in codeine that triggers a true reaction is not usually present in opiates that have a significantly different structure. It's the same premise as why someone can be allergic to shellfish but not meat in general, they can still eat chicken even though it's also a type of animal meat.

The bigger question, is the dose appropriate?

[dura.mater]

Assuming it's a true allergy and not a fairly normal and expected side effect or pseudoallergy symptom, an opiate from the semi-synthetic family (ie hydrocodone) could be tried since there's a decent chance the patient won't be cross reactive. Full synthetics like fentanyl would have the least chance of cross reactivity with a true codeine allergy. The mechanism in codeine that triggers a true reaction is not usually present in opiates that have a significantly different structure. It's the same premise as why someone can be allergic to shellfish but not meat in general, they can still eat chicken even though it's also a type of animal meat.

The bigger question, is the dose appropriate?

All I have on her H&P about it is under allergies it lists codeine- on the physician's orders he has her listed as NKA which is one reason I wondered if it was an error. She's exactly 50 kg and it's 15 mg PO every four hours prn for pain 4-6 and 30 mg for pain 7-10. Even with her age I feel ok about the 15 mg since she is over the 50 kg mark, except for this allergy. I was thinking of asking for a phenylpiperidine like fentanyl, which seems like a scary drug for me, a newbie, to be handing out; or meperidine,but it does have a Beers warning.

So since the hydrocodone is a semi-synthetic it should be OK even though it's also a phenanthrene? What are some questions I can ask to determine if she had a true allergic reaction or psuedoallergy symptom?

Thank you!

[MilliePieRN]

Ask the pt questions and clarify with pharmacy and md. If the pt is on po morphine, more than likely she's already been taking it (check home med list). Ask her "reaction" and hx with opioids. Most allergies listed are adverse reactions. I would think if you acknowledge the allergy, ask pt, and clarify with dr's, you should be fine on your sim lab.

[dura.mater]

Thank you @MilliePieRN! Sounds good to me.