# A teen with cystic fibrosis is starting ivacaftor/tezacaftor/elexacaftor. Which administration instruction is most important for proper absorption?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391794&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A teen with cystic fibrosis is starting ivacaftor/tezacaftor/elexacaftor. Which administration instruction is most important for proper absorption?

## Option

1. Take the medication on an empty stomach
2. Crush the tablets to ease swallowing
3. Take both AM and PM doses with fat-containing food to ensure absorption; do not consume grapefruit **✔ Correct answer**
4. Discontinue dornase alfa and airway clearance therapy

**Correct answer: 3**

## Explanation

Correct (2): CFTR modulators are lipophilic — bioavailability requires fat-containing food with each dose. Grapefruit/Seville orange inhibit CYP3A4 and increase drug levels — avoid. (1) Empty stomach reduces absorption ~80%. (3) Crushing not generally recommended. (4) Dornase alfa and airway clearance continue.

## In-depth explanation

Memory Tip CFTR modulators (Trikafta·Kalydeco) = "Fat-required, Grapefruit-no." LFT monitoring required.

## Clinical scenario

Scenario 16-year-old with cystic fibrosis (heterozygous F508del) starting elexacaftor/tezacaftor/ivacaftor (Trikafta) AM dose and ivacaftor PM dose. Outpatient teaching.

## Key concepts

- **CFTR modulator** — Drugs correcting CFTR protein function in cystic fibrosis; ivacaftor, tezacaftor, elexacaftor, lumacaftor.
- **Fat-containing food** — Required for lipophilic drug absorption; standard counseling for CFTR modulators.
- **CYP3A4 grapefruit interaction** — Grapefruit inhibits CYP3A4, raising CFTR modulator levels; avoid.

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