<p>Cysteamine has a volume of distribution of about 129 L, according to one pharmacokinetic study.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Devereux G, Steele S, Griffiths K, Devlin E, Fraser-Pitt D, Cotton S, Norrie J, Chrystyn H, O'Neil D: An Open-Label Investigation of the Pharmacokinetics and Tolerability of Oral Cysteamine in Adults with Cystic Fibrosis. Clin Drug Investig. 2016 Aug;36(8):605-12. doi: 10.1007/s40261-016-0405-z. (PubMed ID 27153825)" href="#reference-A218941">6</a></sup> Prescribing information indicates a volume of distribution of 382 L for the delayed-release formulation and 198 L for the immediate-release preparation.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA approved products: PROCYSBI (cysteamine bitartrate) delayed-release oral capsules" href="#reference-L15616">12</a></sup>
It is known to cross the blood-brain barrier.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Dohil R, Cabrera BL, Gangoiti JA, Barshop BA, Rioux P: Pharmacokinetics of cysteamine bitartrate following intraduodenal delivery. Fundam Clin Pharmacol. 2014 Apr;28(2):136-43. doi: 10.1111/fcp.12009. Epub 2012 Oct 31. (PubMed ID 23113697)" href="#reference-A218946">8</a></sup></p>