Background and Importance CFTR (cystic fibrosis transmembrane conductance regulator) modulators have meant a significant change in clinical course of cystic fibrosis (CF) patients.

Ivacaftor/tezacaftor/elexacaftor (IVA/TEZ/ELX) are metabolised by cytochrome CYP3A4/5; and tezacaftor and elexacaftor are P-glycoprotein substrates. For this reason, it is essential to review possible drug interactions (DIs) between IVA/TEZ/ELX with drugs, dietary supplements or herbs.

In Spain, dietary supplements and/or herbs use in complex chronic patients was 60–85% in 2021.

Aim and Objectives Identification and evaluation of possible DIs between IVA/TEZ/ELX and dietary supplements and/or herbs in CF adult patients.

Material and Methods Prospective interventional study conducted in an Outpatient Pharmaceutical Care Unit (OPCU) from December 2021-March 2022 that included CF adult patients who started IVA/TEZ/ELX.

Following OPCU protocol, a first structured pharmaceutical care (PC) visit was conducted at the start of IVA/TEZ/ELX to inform about dosage, administration, DIs, precautions, and adverse reactions.

Biodemographic data, F508del mutation, previous CFTR modulators and concomitant dietary supplements and/or herbs were collected.

Results 104 patients (53 women, median age 28.3(21.9–36.7) years) were included; 65 patients (62.5%) were heterozygous for F508del mutation. One patient was in previous treatment with ivacaftor, 48 patients with ivacaftor/tezacaftor and 13 patients in clinical trial or managed access programs with IVA/TEZ/ELX.

We identified 14 patients (9 women) with median age 35.1(22.1–40.0) years who took dietary supplements and/or herbs at the start of IVA/TEZ/ELX, 13.5% of all patients.

Possible CYP3A4/5 DIs (Silybum marianum, Curcuma longa, Hypericum perforatum, Bacopa Monnieri, Ginkgo biloba, Citrus aurantium and Vaccinium) were identified in five patients. Due to the possible DIs, pharmaceutical recommendation was the withdrawal of the supplements or herbs, which were suspended in all cases. In one patient, possible P-glycoprotein DI was detected (Boswellia serrata), but removal was not considered necessary.

Conclusion and Relevance Dietary supplements and/or herbs use in our population was lower than in other complex chronic patients. However, identification of possible DIs led to the withdrawal of the supplements and/or herbs in approximately one third of the patients.

DIs with IVA/TEZ/ELX can have great clinical relevance and impact on health outcomes. Therefore, the review of concomitant treatments in the PC visit is essential to guarantee the effectiveness and safety of IVA/TEZ/ELX.

Conflict of Interest No conflict of interest