# Situation: A 52-year-old man comes to the clinic with sudden, severe pain, redness and swelling of the right big toe that began during the night after a party with beer and grilled meat. He takes hydrochlorothiazide for hypertension. His kidney function is normal. Colchicine is prescribed for the flare. Reviewing his current medications, which one should the nurse bring to the prescriber's attention because of the risk of colchicine toxicity?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=630436  
> language: ko  
> subject: Nursing Practice IV — Care of Clients with Problems in Nutrition and Gastrointestinal, Metabolism and Endocrine, Perception and Coordination

## 문제

Situation: A 52-year-old man comes to the clinic with sudden, severe pain, redness and swelling of the right big toe that began during the night after a party with beer and grilled meat. He takes hydrochlorothiazide for hypertension. His kidney function is normal.

Colchicine is prescribed for the flare. Reviewing his current medications, which one should the nurse bring to the prescriber's attention because of the risk of colchicine toxicity?

## 보기

1. Losartan 50 mg daily recently added for blood pressure
2. Hydrochlorothiazide taken daily for hypertension
3. Clarithromycin started 2 days ago for sinusitis **✔ 정답**
4. Aspirin 80 mg daily taken for heart protection

**정답: 3**

## 해설

Strong CYP3A4 and P-glycoprotein inhibitors such as clarithromycin block colchicine elimination and can cause severe or fatal colchicine toxicity, so the dose must be changed or the combination avoided. Thiazide diuretics and low-dose aspirin affect urate levels, which is a different problem from colchicine toxicity.

## 심화 해설

A dangerous interaction
Colchicine is eliminated through the liver enzyme CYP3A4 and the efflux transporter P-glycoprotein. Strong inhibitors of CYP3A4 and P-glycoprotein, such as clarithromycin, block colchicine elimination and can cause severe or fatal colchicine toxicity. The client started clarithromycin 2 days ago for sinusitis, so the nurse brings this combination to the prescriber's attention before colchicine is given. The prescriber may reduce the colchicine dose, choose a different drug for the flare, or change the antibiotic.

What colchicine toxicity looks like
Colchicine has a narrow therapeutic range. Early toxicity causes nausea, vomiting, abdominal pain, and diarrhea. With higher levels it can progress to bone marrow suppression, muscle damage (myopathy or rhabdomyolysis), nerve damage, and multiorgan failure. Gastrointestinal symptoms are therefore an early signal to stop and report. Risk increases with kidney or liver impairment and with interacting drugs. Other strong interacting drugs include some azole antifungals, certain protease inhibitors, ciclosporin, and verapamil or diltiazem.

Why the other medications are not the concern
The distractors are drugs that matter in gout, but not for colchicine toxicity.

| Drug | Relevance to gout | Colchicine toxicity risk? |
| --- | --- | --- |
| Losartan | Modest uricosuric effect | No; does not affect colchicine clearance |
| Hydrochlorothiazide | Raises serum urate and can provoke gout | No |
| Clarithromycin | None | Yes; strong CYP3A4 and P-glycoprotein inhibitor |
| Low-dose aspirin | Slightly raises serum urate | No; and it is not stopped without the prescriber |

Watch out! Hydrochlorothiazide is a tempting answer because thiazides are a known cause of gout. The question, however, asks about colchicine toxicity, not about urate levels. Read exactly what risk the stem names.

Nursing practice
During medication reconciliation the nurse looks specifically for macrolide antibiotics, azole antifungals, and other strong enzyme inhibitors in any client starting colchicine, and teaches the client to report diarrhea, vomiting, muscle weakness, or numbness. Clients are also taught not to take extra colchicine doses on their own. Key point! Colchicine plus a strong CYP3A4 or P-glycoprotein inhibitor such as clarithromycin can be fatal; report the combination before the dose is given.

## 임상 시나리오

Colchicine Drug InteractionClarithromycin and toxicity risk
Colchicine is cleared by CYP3A4 and P-glycoprotein. Clarithromycin strongly inhibits both, so colchicine accumulates.

Toxicity starts with diarrhea, vomiting, and abdominal pain and can progress to marrow suppression, myopathy, and organ failure.

Thiazides and low-dose aspirin affect urate levels, which is a different issue; losartan does not interfere with colchicine.

CautionReport the clarithromycin before giving colchicine; the dose must be changed or the combination avoided.

## 핵심 개념

- **Colchicine** — An anti-inflammatory drug used to treat and prevent gout flares; it has a narrow therapeutic range.
- **CYP3A4** — A liver and intestinal enzyme that metabolizes many drugs; inhibitors raise the blood levels of those drugs.
- **P-glycoprotein** — A transporter that pumps drugs out of cells into bile, urine, or the gut lumen, aiding their elimination.
- **Clarithromycin** — A macrolide antibiotic that strongly inhibits CYP3A4 and P-glycoprotein.

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