A spreading rash, blistering, or mucosal involvement may be Stevens-Johnson syndrome - stop the drug and report immediately.
Before you read
Test yourself first: 2 questions
Question 1 of 2
A nurse reviews new orders for a client with a documented severe allergy to sulfa drugs. Which prescribed medication should the nurse question?
Answer: A. Trimethoprim-sulfamethoxazole contains a sulfonamide and is contraindicated in a client with a severe sulfa allergy; the nurse should question this order. Amoxicillin, azithromycin, and doxycycline are not sulfonamides and do not pose a sulfa cross-reaction.
Question 2 of 2
A client is started on trimethoprim-sulfamethoxazole (TMP-SMX). Which instruction is most important for the nurse to provide?
Answer: A. Sulfonamides require a high fluid intake to prevent crystalluria and renal stone formation, and clients should report rash because of the risk of Stevens-Johnson syndrome. Increasing fluids is the key prevention teaching. The drug is not taken with iron specifically, does not require a low-protein diet, and is not given only at bedtime.
Keep the streak going with more questions like these, each with a full rationale.
What is sulfonamides?
They are notable for causing severe skin reactions like Stevens-Johnson syndrome and for hyperkalemia. The key principle is high fluid intake and watching for rash and hyperkalemia.
Key points to remember
- Sulfonamides are bacteriostatic and inhibit folic acid synthesis in bacteria.
- They can cause Stevens-Johnson syndrome and other severe hypersensitivity skin reactions.
- They cause crystalluria, so adequate fluid intake is essential.
- Trimethoprim-sulfamethoxazole can cause hyperkalemia, especially with ACE inhibitors or potassium supplements.
- They potentiate warfarin, sulfonylureas, and phenytoin, increasing the risk of bleeding and hypoglycemia.
- They are avoided near term in pregnancy and in newborns because of kernicterus risk.
Nursing priorities
- Screen for sulfa allergy before giving and assess for prior reactions.
- Encourage at least 2 to 3 liters of fluid per day to prevent crystalluria.
- Inspect the skin and stop the drug at the first sign of rash.
- Monitor potassium and INR in at-risk patients.
- Monitor blood glucose in diabetics taking sulfonylureas.
Labs & values
Patient teaching
- Drink plenty of water throughout the day to protect your kidneys.
- Stop the drug and call your provider at the first sign of a rash or mouth sores.
- Use sunscreen because of photosensitivity.
- Report fever, sore throat, or easy bruising.
Red flags: report now
- A spreading rash, blistering, or mucosal involvement may be Stevens-Johnson syndrome - stop the drug and report immediately.
- Signs of hyperkalemia such as muscle weakness or arrhythmia must be reported.
- Sore throat, fever, or unusual bruising may signal blood dyscrasia and must be reported.
References
Clinical references for this topic
