Pharmacokinetics in Patients with Cystic Fibrosis: A Systematic Review of Data Published Between 1999 and 2019

Cystic fibrosis is a lethal inherited disease that affects multiple organs. To provide optimal pharmacological treatment of comorbidities associated with cystic fibrosis, relevant alterations in pharmacokinetics must be known.

The objective of this study was to compare the pharmacokinetics of drugs between patients with cystic fibrosis and controls, based on clinical study reports published from 1999 to 2019.

Clinical studies were considered if patients with cystic fibrosis and patients without cystic fibrosis/healthy volunteers were included, a drug was administered orally/intravenously and pharmacokinetic parameters were compared.

In total, 32 clinical studies were included. Twenty-one studies reported absorption parameters. For multiple drugs, speed and/or extent of oral absorption were lower in cystic fibrosis. This phenomenon is possibly related to pathophysiological changes in the gastrointestinal tract associated with cystic fibrosis. However, a large proportion of drugs had comparable absorption kinetics. Twenty-one studies discussed volume of distribution, which was comparable between groups for most drugs. Initial differences became smaller when scaled to body composition. For some highly protein-bound drugs, inflammation-related changes in plasma proteins helped explain residual variability between cystic fibrosis and controls. Twenty-four studies elaborated on clearance, whereby higher clearances were observed in cystic fibrosis. In contrast with previously published reviews, no evidence was found for increased activities of drug-metabolising enzymes nor for up-regulation of active transport processes involved in drug disposition. In most cases, scaling clearance parameters to body composition and/or incorporating differences in plasma protein concentration accounted for these larger clearances.

There is no evidence that genetic defects causing cystic fibrosis directly lead to altered pharmacokinetics. However, co-morbidities can have a potential impact on drug absorption and disposition. Because of gastrointestinal complications, it is not advisable to extrapolate drug absorption parameters from healthy volunteers to patients with cystic fibrosis. Differences observed in the volume of distribution and clearance in patients with cystic fibrosis can potentially be explained by correcting for lean body mass.