# A 35-year-old client with uncomplicated UTI is being discharged on trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim DS) one tablet PO twice daily for 5 days. Which client teaching is most important?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=375239&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A 35-year-old client with uncomplicated UTI is being discharged on trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim DS) one tablet PO twice daily for 5 days. Which client teaching is most important?

## Option

1. Stop the medication once urinary symptoms resolve.
2. Crush the tablet and mix it with antacid for absorption.
3. Drink at least 8 to 10 glasses of water daily to prevent crystalluria, complete the entire 5-day course, avoid sun and use sunscreen because of photosensitivity, report rash, blistering, mucosal sores, fever, swelling, or breathing difficulty immediately, and report a known sulfa allergy if not already documented. **✔ Correct answer**
4. Take it with milk and limit fluids to keep the urine concentrated.

**Correct answer: 3**

## Explanation

Trimethoprim-sulfamethoxazole (TMP-SMX) is a sulfa-containing combination antibiotic widely used for uncomplicated UTI, otitis media, traveler diarrhea, MRSA skin and soft tissue, Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment, and other indications. Important client teaching: (1) hydrate well — at least 8 to 10 glasses of water daily — to prevent crystalluria; (2) complete the prescribed course on schedule; (3) photosensitivity — apply sunscreen, wear protective clothing, avoid prolonged sun and tanning beds; (4) sulfa hypersensitivity — confirmed allergy is a contraindication; report rash (especially diffuse, painful, blistering, with mucosal involvement of mouth/eyes/genitals) which may signal Stevens-Johnson Syndrome or toxic epidermal necrolysis (SJS/TEN); call 911 or go to ED immediately if SJS features develop; (5) hematologic effects — agranulocytosis, thrombocytopenia, hemolytic anemia (especially in G6PD deficiency), megaloblastic anemia from folate antagonism; report fatigue, fever, easy bruising, jaundice; (6) hyperkalemia — TMP blocks the renal epithelial sodium channel similar to amiloride; risk increases with elderly, renal impairment, ACE inhibitor or ARB, potassium-sparing diuretic, or potassium supplements; (7) avoid late in pregnancy due to kernicterus and folate effects; (8) crystalluria, AKI, drug interactions with warfarin (INR up), methotrexate, sulfonylureas, and others; review pharmacist consult. Milk and reduced fluid, stopping early, and crushing with antacid are unsafe.

## In-depth explanation

Hydrate, complete course, sunscreen, watch for SJS rash and bone marrow effects. Hyperkalemia risk in elderly with RAAS blockers is the high-yield interaction.

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