1. Academic Validation
  2. Drug solubility in biorelevant media in the context of an inhalation-based biopharmaceutics classification system (iBCS)

Drug solubility in biorelevant media in the context of an inhalation-based biopharmaceutics classification system (iBCS)

  • Eur J Pharm Biopharm. 2024 Feb 3:114206. doi: 10.1016/j.ejpb.2024.114206.
Andreea Floroiu 1 Brigitta Loretz 2 Johannes Krämer 3 Claus-Michael Lehr 4
Affiliations

Affiliations

  • 1 Department of Pharmacy, Saarland University, 66123 Saarbrücken, Germany; Eurofins PHAST Development GmbH & Co. KG, 78467 Konstanz, Germany. Electronic address: Andreea.Floroiu@bpt.eurofinseu.com.
  • 2 Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research, Saarland University, Campus E8 1, 66123 Saarbrücken, Germany.
  • 3 DISSO GmbH, 66424 Homburg, Germany.
  • 4 Department of Pharmacy, Saarland University, 66123 Saarbrücken, Germany; Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research, Saarland University, Campus E8 1, 66123 Saarbrücken, Germany. Electronic address: Claus-Michael.Lehr@helmholtz-hips.de.
Abstract

An inhalation-based Biopharmaceutical Classification System for pulmonary drugs (iBCS) holds the perspective to allow for scientifically sound prediction of differences in the in vivo performance of orally inhaled drug products (OIDPs). A set of nine drug substances were selected, that are administered via both the oral and pulmonary routes. Their solubility was determined in media representative for the oral (Fasted State Simulated Intestinal Fluid (FaSSIF)) and pulmonary (Alveofact medium and Simulated Lung Fluid (SLF)) routes of administration to confirm the need for a novel approach for inhaled drugs. The complexity of these media was then stepwise reduced with the purpose of understanding the contribution of their components to the solubilizing capacity of the media. A second reason for varying the complexity was to identify a medium that would allow robust but accurate dissolution testing. Hence, Hank's balanced salt solution (HBSS) as a medium used in many in vitro biological tests, non-buffered saline solution and water were included. For some drug substances (salbutamol sulfate, tobramycin, isoniazid, and tiotropium bromide), no significant differences were observed between the solubility in the media used. For other drugs, however, we observed either just small (rifampicin, budesonide, salmeterol) or unexpectedly large differences (beclomethasone dipropionate). Based on the minimum theoretical solubility required for their common pulmonary dose in 10 ml of lung lining fluid, drug solubility was classified as either high or low. Two high solubility and two low solubility compounds were then selected for refined solubility testing in pulmonary relevant media by varying their content of Phospholipids, surfactant proteins and other proteins. The solubility of drug substances in simulated lung lining fluids was found to be dependent on the physicochemical properties of the drug substance and the composition of the media. While a pulmonary dissolution medium that would fit all drugs could not be established, our approach may provide guidance for finding the most suitable dissolution medium for a given drug substance and better designing in vitro tests for predicting the in vivo performance of inhalable drug products.

Keywords

Dissolution testing; Inhalation biopharmaceutics classification system; Orally inhaled drug products; Pulmonary solubility.

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