The mechanism is selective for the CFTR and CaCC, as other channels involved in intestinal fluid secretion, namely sodium and potassium channels, are not affected by crofelemer, nor is cAMP or calcium signaling.Crofelemer is minimally, if at all, absorbed from the gut into the bloodstream, and is mostly excreted in the stools. Adverse effects and interactions
Crofelemer is well tolerated; and the only adverse effects found in clinical studies were mild gastrointestinal effects at the same level as under placebo. The most common adverse reactions (≥ 3%) are: upper respiratory tract infection, bronchitis, cough, flatulence and increased bilirubin. Origin and chemistry
Crofelemer is an oligomeric proanthocyanidin mixture primarily composed of (+)–catechin, (–)–epicatechin, (+)–gallocatechin, and (–)–epigallocatechin monomer units linked in random sequence, as represented below. The average degree of polymerization for the oligomers ranges between 5 and 7.5, as determined by phloroglucinol degradation. The substance is a purified oligomeric proanthocyanidin from the sap, or more correctly the latex, of the South American tree Croton lechleri (locally called Sangre de Grado or Sangre de Drago). This is one of several plants producing bright red latex or resin called "dragons blood". Crofelemer is a complex mixture of procyanidins and prodelphinidins with up to 30 (epi)catechin or (epi)gallocatechin units per molecule, resulting in a molecular mass of up to 9 kDa. History of Crude Plant Latex (Dragons Blood) and Crofelemer
The crude plant latex of C. lechleri is traditionally used in South American medicine for the treatment of diarrhea, wounds, inflammations, tumors, insect bites, and other conditions.
The Practice of Oxygen Measurement for Divers. Flagstaff: Best Publishing, 120 pages. ISBN 0-941332-68-3. OCLC 44018369. Lippmann, John; Bugg, Stan (1993). The Diving Emergency Handbook. Teddington, UK: Underwater World Publications. ISBN 0-946020-18-3. OCLC 52056845. Lippmann, John; Mitchell, Simon (2005). "Oxygen". Deeper into Diving (2nd ed.). Victoria, Australia: J.L. Publications. pp. 121–24. ISBN 0-9752290-1-X. OCLC 66524750. External links
General
The following external site is a compendium of resources:

Rubicon Research Repository Archived 8 September 2012 at the Wayback Machine – Online collection of the oxygen toxicity researchSpecialised
The following external sites contain resources specific to particular topics:

2008 Divers Alert Network Technical Diving Conference – Video of "Oxygen Toxicity" lecture by Dr. Richard Vann (free download, mp4, 86MB). Nosek, Thomas M. "Section 4/4ch7/s4ch7_7". Essentials of Human Physiology. Archived from the original on 24 March 2016. – Discussion of the effects of breathing oxygen on the respiratory system. Rajiah, Prabhakar (11 March 2009). "Bronchopulmonary Dysplasia". eMedicine. WebMD. Retrieved 29 June 2009. – Clinical overview with references.