Management of Cystic Fibrosis

Question 1

What is the inheritance pattern of cystic fibrosis (CF)?

Answer 1

Autosomal recessive.

Question 2

What is the most common CFTR mutation in cystic fibrosis?

Answer 2

F508del.

Question 3

How is CF diagnosed?

Answer 3

Positive newborn screen, symptoms + sweat chloride > 60 mEq/L, or known CFTR mutation.

Question 4

What CFTR modulator is used for patients with at least one F508del mutation?

Answer 4

Trikafta (elexacaftor/tezacaftor/ivacaftor).

Question 5

What is a key counseling point for all CFTR modulators?

Answer 5

Take with fatty foods and monitor LFTs regularly.

Question 6

Which CFTR modulator has CYP3A interactions and requires eye exams?

Answer 6

Ivacaftor and all combinations containing ivacaftor.

Question 7

What is the mechanism of action of dornase alfa?

Answer 7

Cleaves extracellular DNA to reduce mucus viscosity in lungs.

Question 8

What is the role of hypertonic saline in CF?

Answer 8

Creates an osmotic gradient to draw water into airways and thin mucus.

Question 9

What is a key side effect of inhaled mannitol?

Answer 9

Bronchospasm; requires a tolerance test before use.

Question 10

Why is double coverage used for Pseudomonas in CF?

Answer 10

To provide synergy and prevent resistance; different mechanisms of action are used.

Question 11

What is a common inhaled antibiotic regimen for chronic Pseudomonas?

Answer 11

Tobramycin 300 mg inhaled BID, 28 days on/off.

Question 12

What IV beta-lactams are used for CF exacerbations?

Answer 12

Zosyn, cefepime, ceftazidime, meropenem (dosed q8h, often extended infusion).

Question 13

How are aminoglycosides dosed in CF?

Answer 13

Once daily dosing (e.g., tobramycin 12 mg/kg IV q24h); monitor peak and trough.

Question 14

What is the starting dose for pancreatic enzymes in CF?

Answer 14

1000 units of lipase/kg/meal, max 10,000 units/kg/day.

Question 15

How is enzyme dose adjusted in CF?

Answer 15

Based on number of stools/day, stool fat content, and weight gain.

Question 16

What vitamins should be monitored and supplemented in CF?

Answer 16

Vitamins A, D, E, K (fat-soluble).

Question 17

How is CFRD screened for in patients over age 10?

Answer 17

Annual oral glucose tolerance test (OGTT).

Question 18

What is the insulin-to-carb ratio in CFRD?

Answer 18

0.5–1 unit per 15 grams of carbs; adjusted based on postprandial glucose.

Question 19

What airway clearance therapies are used in CF?

Answer 19

Chest physiotherapy, therapy vest, flutter valve, huff coughing.

Question 20

What is the use of azithromycin in CF?

Answer 20

Immunomodulatory effect; used in chronic Pseudomonas infection.

Question 21

What are common side effects of ivacaftor?

Answer 21

Headache, dizziness, upper respiratory tract infection, elevated LFTs, cataracts.

Question 22

What are key monitoring parameters for Trikafta (elexacaftor/tezacaftor/ivacaftor)?

Answer 22

ALT/AST (baseline and during treatment), eye exams in pediatric patients, respiratory status.

Question 23

What is a serious but rare side effect of CFTR modulators?

Answer 23

Liver toxicity; elevated transaminases may require dose adjustment or discontinuation.

Question 24

What are the side effects of dornase alfa (Pulmozyme)?

Answer 24

Voice alteration, sore throat, laryngitis, rash.

Question 25

What are potential adverse effects of hypertonic saline inhalation?

Answer 25

Cough, bronchospasm, throat irritation.

Question 26

What is a common side effect of inhaled mannitol?

Answer 26

Bronchospasm; requires tolerance testing prior to initiation.

Question 27

What are common side effects of inhaled tobramycin?

Answer 27

Tinnitus, voice alteration, bronchospasm, increased cough.

Question 28

What toxicities are associated with IV aminoglycosides (e.g., tobramycin)?

Answer 28

Nephrotoxicity and ototoxicity; monitor peaks/troughs.

Question 29

What side effects can occur with long-term azithromycin in CF?

Answer 29

GI upset, QT prolongation, and potential for resistance.

Question 30

What are side effects of pancreatic enzyme replacement therapy?

Answer 30

Constipation, abdominal pain, fibrosing colonopathy (high doses).

Question 31

What are common side effects of insulin in CF-related diabetes (CFRD)?

Answer 31

Hypoglycemia, weight gain, injection site reactions.

Question 32

How is cystic fibrosis inherited and diagnosed?

Answer 32

CF is inherited in an autosomal recessive pattern. Diagnosis is based on newborn screening, symptoms with sweat chloride >60 mEq/L, or identification of two disease-causing CFTR mutations.

Question 33

What is the role of CFTR modulators in CF management?

Answer 33

CFTR modulators improve CFTR protein function. Trikafta (elexacaftor/tezacaftor/ivacaftor) is used for patients with at least one F508del mutation.

Question 34

What monitoring is necessary when initiating CFTR modulators?

Answer 34

Monitor liver function (ALT/AST), perform baseline and annual eye exams (in pediatrics), and assess for drug-drug interactions via CYP3A.

Question 35

What is the function of airway clearance therapies in CF?

Answer 35

They mobilize and clear thick mucus to reduce infection risk and improve lung function (e.g., dornase alfa, hypertonic saline, physiotherapy).

Question 36

What are recommended antibiotics for Pseudomonas infections in CF?

Answer 36

Inhaled tobramycin (chronic), IV tobramycin + beta-lactam (acute), with double coverage for resistance prevention.

Question 37

How is pancreatic insufficiency treated in CF?

Answer 37

Pancreatic enzyme replacement therapy (e.g., Creon, Zenpep) with meals and snacks; dosing based on weight and fat intake.

Question 38

What is the nutritional support required for CF patients?

Answer 38

High-calorie diet, fat-soluble vitamin supplementation (A, D, E, K), and routine nutritional assessments.

Question 39

What are strategies for managing CF-related diabetes (CFRD)?

Answer 39

Insulin therapy based on glucose monitoring and carb intake; screening starts annually at age ≥10 with OGTT.

Question 40

What inhaled antibiotics are commonly used for chronic Pseudomonas in CF?

Answer 40

Tobramycin inhalation solution or powder (300 mg BID for 28 days on/off), or aztreonam lysine.

Question 41

What is the rationale for using inhaled antibiotics in CF?

Answer 41

To target airway infections directly, reduce bacterial burden, and improve lung function while minimizing systemic toxicity.

Question 42

What IV antibiotics are typically used for acute CF pulmonary exacerbations with Pseudomonas?

Answer 42

Tobramycin IV + an antipseudomonal beta-lactam (e.g., cefepime, piperacillin-tazobactam, or meropenem).

Question 43

What beta-lactams are used for Pseudomonas coverage in CF?

Answer 43

Cefepime, ceftazidime, piperacillin-tazobactam, meropenem.

Question 44

Why is double antibiotic coverage used for Pseudomonas in CF exacerbations?

Answer 44

To reduce resistance development and improve efficacy through synergy.

Question 45

How are aminoglycosides like tobramycin dosed for CF exacerbations?

Answer 45

Once daily dosing (e.g., 12 mg/kg IV q24h), adjusted based on peak and trough levels.

Question 46

When should oral antibiotics be used in CF exacerbations?

Answer 46

In mild cases or as step-down therapy based on culture and susceptibility results.

Question 47

What is the role of azithromycin in CF?

Answer 47

Used chronically in patients with Pseudomonas colonization for its anti-inflammatory effects, not as an acute antibiotic.