Cystic Fibrosis: Medication Adherence Is Key

Cystic fibrosis (CF) is an inherited genetic disorder resulting from the mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene located on chromosome 7. This mutation results in improper transcellular movement of water and electrolytes (namely sodium and chloride) across epithelial layers, resulting in viscous secretions. Because of the abnormally increased viscosity of these secretions, mucociliary obstruction and inflammation occurs. Although these secretions mostly occur in the pulmonary epithelia, they can also affect key ducts in the gastrointestinal tract, depending on a patient’s phenotype.^1-6

CF usually affects the respiratory and digestive systems. Regarding the respiratory effects, CF typically causes an increase in chest diameter, a productive or dry cough, wheezing, recurrent respiratory tract infections, and bloody sputum. Regarding the digestive effects, CF may cause constipation, abdominal distension, and foul-smelling, fatty stools. Because of these effects, children with CF may have difficulty gaining weight and growing. Patients with CF may also have especially salty sweat.^1-6

Multiple tests exist for properly diagnosing CF. Most commonly, the sweat test, also known as pilocarpine iontophoresis, has been used to diagnose CF. Although this test has been used as a gold standard for CF diagnosis, multiple barriers to its use exist, such as lack of equipment and specialists, cost, and difficulty with sample collecting and processing. Gonçalves et al conducted a study on using a saliva test on healthy patients versus patients with CF and found that sodium and chloride levels were higher in patients with CF; however, more studies are needed to determine “normal” ion concentrations for patients with CF, based on age, genotype, and environment.^1-6

Antibiotics

Respiratory treatment of CF includes airway clearance and the use of antibiotics for recurring infections. In addition to parenteral antibiotics, inhaled antibiotics act directly in the airway with minimal systemic absorption. Inhaled tobramycin (TOBI) was approved by the FDA in 1999 and was initially administered in an ampule via nebulizer for patients with CF and chronic Pseudomonas aeruginosa infection. In 2013, a more convenient formulation—TOBI Podhaler (via inhaled powder)— was approved by the FDA. Other antibiotics for treating P. aeruginosa infection include inhaled aztreonam (Cayston) and oral azithromycin. The latter has also been shown to improve lung function and weight gain and decrease hospitalization rates. Other anti-infective agents in the pipeline include inhaled levofloxacin, inhaled liposomal amikacin, and vancomycin inhalation powder.^2,6

Other aerosolized inhalation agents include dornase alfa (Pulmozyme), which can be used to decrease sputum viscosity and improve sputum expectoration. Because dornase alfa is denatured, it cannot be mixed with other aerosol medications. In addition, hypertonic saline (3%-10% concentration) has been used to increase the volume of the airway epithelial lining, resulting in normal ciliary flow and increased sputum expectoration. Aerosolized products currently being studied include a powdered form of mannitol.^2,6

To manage inflammation—a common pulmonary manifestation of CF—the use of high-dose, long-term ibuprofen has demonstrated a reduced rate of lung function decline in patients with CF.^2,6

Nutrition

Pancreatic enzyme replacement therapy (PERT) is used in patients with CF and pancreatic insufficiency. PERT is available in multiple concentrations and in formulations containing lipase, amylase, and protease from animal sources, which are to be taken with meals or snacks (or enteral feeds). Because fats are not properly absorbed in patients with CF, the fat-soluble vitamins A, D, E, and K (AquaDEKs) are given to prevent deficiencies. Liprotamase—a PERT currently undergoing phase 3 studies—is not prepared from animal sources.^2,6

CFTR Modulators

Two medications (ie, ivacaftor and lumacaftor/ivacaftor) have been approved by the FDA to correct the function of defective CFTR proteins. Ivacaftor (Kalydeco) potentiates opening of the chloride channel to allow more electrolyte movement intracellularly and extracellularly. The addition of lumacaftor to ivacaftor (Orkambi) not only improves CFTR function, but also properly relocates defective CFTR proteins.^2,6

Role of the Pharmacist

Although adherence is important for all patients, patients with CF can face serious consequences of poor adherence, such as an increased rate of lung function decline, exacerbations, and increased hospitalization rates. Therefore, it is imperative for health care providers, including pharmacists, to educate patients with CF, and their caregivers, about medication adherence. Because some medications for CF are not available in oral formulations, pharmacists must show patients how to properly administer these medications to help ensure adherence. Pharmacists should also contribute to clinical research as investigators or collaborators.

Brian J. Catton, PharmD, graduated from the Bernard J. Dunn School of Pharmacy at Shenandoah University in Winchester, Virginia, in 2010. He received the Distinguished Young Pharmacist Award from the New Jersey Pharmacists Association, in 2014, and founded its New Practitioner Network in 2015. He is a scientific communications manager at Alpha- BioCom in King of Prussia, Pennsylvania. His areas of interest include pediatrics, immunizations, drug-therapy management, social media, patient counseling, and immuno-oncology.

References

• Caraher M-T, Marshall S. Cystic fibrosis related diabetes: causes, impact on health and management of patients. Eur Diabetes Nursing. 2014;11(3):85-91.
• Phan H, Kuhn R. Cystic fibrosis. In: Benavides S, Nahata MC, eds. Pediatric Pharmacotherapy. Lenexa, KS: ACCP; 2013:223-242.
• Borowitz D. CFTR, bicarbonate, and the pathophysiology of cystic fibrosis. Pediatr Pulmonol. 2015;50(suppl 40):S24-S30. doi: 10.1002/ppul.23247.
• Gonçalves AC, Marson FA, Mendonça RM, et al. Saliva as a potential tool for cystic fibrosis diagnosis. Diagn Pathol. 2013;8:46:1-7. doi: 10.1186/1746-1596-8-46.
• Lubamba B, Dhooghe B, Noel S, Leal T. Cystic fibrosis: Insight into CFTR pathophysiology and pharmacotherapy. Clin Biochem. 2012;45(15):1132-1144. doi: 10.1016/j.clinbiochem.2012.05.034.
• Cystic Fibrosis Foundation. Drug development pipeline. CFF website. tools.cff.org/research/drugdevelopmentpipeline. Accessed March 3, 2016.