# A 72-year-old client with chronic stable angina is being instructed on a nitroglycerin transdermal patch applied each morning. Which instruction is most important to prevent nitrate tolerance?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=374935&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A 72-year-old client with chronic stable angina is being instructed on a nitroglycerin transdermal patch applied each morning. Which instruction is most important to prevent nitrate tolerance?

## Option

1. "Remove the patch each evening and remain patch-free for 10-12 hours overnight to preserve the medication effectiveness." **✔ Correct answer**
2. "Apply the patch to the same site on the chest daily after washing to promote uniform absorption of the drug."
3. "Place the patch over a hairy portion of the chest to help the patch stay in place and increase absorption."
4. "If a patch becomes detached, apply two new patches the next morning to replace the missed dose and ensure adequate drug levels."

**Correct answer: 1**

## Explanation

Nitrate tolerance and patch-free interval
Continuous exposure to nitrates produces tolerance within 24-48 hours, with loss of antianginal effect. To preserve efficacy, dosing must include a nitrate-free interval of 10-14 hours per 24 hours; for transdermal patches the standard is to apply the patch in the morning and remove it at bedtime. (Patients with predominantly nocturnal angina may invert the schedule.) Other patch teaching:
• Rotate sites daily — clean, dry, hairless, non-irritated skin (chest, upper arm, back); avoid scars, cuts, hairy areas.
• Wash hands after application; remove old patch before applying new.
• Do not cut the patch (alters delivery rate).
• Avoid heating pads or hot environment near the patch (accelerates release → severe hypotension).
• Skin reactions (redness, itching) — rotate site.
• During cardioversion or defibrillation, remove the patch (metallic backing arc/burn).
• Same contraindication: PDE5 inhibitor (sildenafil/tadalafil/vardenafil) within 24-48 hours = absolute.

## In-depth explanation

Clinical reasoning summary
Nitrate tolerance and patch-free interval
Continuous exposure to nitrates produces tolerance within 24-48 hours, with loss of antianginal effect. To preserve efficacy, dosing must include a nitrate-free interval of 10-14 hours per 24 hours; for transdermal patches the standard is to apply the patch in the morning and remove it at bedtime. (Patients with predominantly nocturnal angina may invert the schedule.) Other patch teaching:
• Rotate sites daily — clean, dry, hairless, non-irritated skin (chest, upper arm, back); avoid scars, cuts, hairy areas.
• Wash hands after application; remove old patch before applying new.
• Do not cut the patch (alters delivery rate).
• Avoid heating pads or hot environment near the patch (accelerates release → severe hypotension).
• Skin reactions (redness, itching) — rotate site.
• During cardioversion or defibrillation, remove the patch (metallic backing arc/burn).
• Same contraindication: PDE5 inhibitor (sildenafil/tadalafil/vardenafil) within 24-48 hours = absolute.

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