# A 30-year-old client is starting doxycycline 100 mg PO twice daily for atypical pneumonia. Which client teaching is most important?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=375244&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A 30-year-old client is starting doxycycline 100 mg PO twice daily for atypical pneumonia. Which client teaching is most important?

## Option

1. Take it with milk and an antacid for best absorption.
2. Crush the tablet for easier swallowing.
3. Take with a full glass of water in an upright position to avoid esophageal irritation; separate from dairy, calcium, magnesium, iron, zinc, antacids, and bismuth by 2 hours; use sunscreen for photosensitivity; avoid pregnancy and use in children under 8 years; complete the prescribed course; report severe diarrhea, jaundice, or headache. **✔ Correct answer**
4. Stop the medication once the cough improves.

**Correct answer: 3**

## Explanation

Doxycycline is a tetracycline antibiotic used for atypical pneumonia (Mycoplasma, Chlamydophila, Legionella), tickborne illnesses (Lyme, Rocky Mountain spotted fever), chlamydia, MRSA skin and soft tissue, malaria prophylaxis, acne, and others. Key teaching: (1) absorption is significantly reduced by polyvalent cations — separate by 2 hours from dairy, calcium, magnesium, iron, zinc, aluminum-containing antacids, sucralfate, bismuth subsalicylate; (2) take with a full glass of water and remain upright for 30 minutes to prevent pill esophagitis and esophageal ulceration; (3) photosensitivity is common — apply sunscreen, wear protective clothing, avoid prolonged sun and tanning beds; (4) tetracyclines are contraindicated in pregnancy and in children under 8 years because they bind calcium in developing bones and teeth, causing permanent yellow-brown discoloration and enamel hypoplasia, with possible bone growth retardation; (5) GI side effects — nausea, vomiting, diarrhea; report severe or bloody (C. difficile); (6) hepatotoxicity, particularly with high doses or in pregnancy; (7) intracranial hypertension (pseudotumor cerebri) — report severe headache, blurred vision, papilledema; (8) candidiasis with prolonged use; (9) interactions — warfarin (INR up), digoxin (level up), oral contraceptives (possible decreased efficacy), retinoids (additive intracranial hypertension). Milk/antacid, stopping early, and crushing are not the priority.

## In-depth explanation

Full water + upright posture + 2-hour cation spacing + sunscreen + pregnancy and pediatric avoidance summarize doxycycline teaching. Pill esophagitis and tooth staining are highly tested.

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