<p>Orally administered cysteamine is absorbed in the gastrointestinal tract and reaches its maximum plasma concentration in about 1.4 hours, with some variation according to the type of formulation (delayed versus immediate-release).<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>,<a class="reference-popover-link" data-content="Gangoiti JA, Fidler M, Cabrera BL, Schneider JA, Barshop BA, Dohil R: Pharmacokinetics of enteric-coated cysteamine bitartrate in healthy adults: a pilot study. Br J Clin Pharmacol. 2010 Sep;70(3):376-82. doi: 10.1111/j.1365-2125.2010.03721.x. (PubMed ID 20716238)" href="#reference-A218936">5</a>,<a class="reference-popover-link" data-content="FDA approved products: PROCYSBI (cysteamine bitartrate) delayed-release oral capsules" href="#reference-L15616">12</a></sup> One pharmacokinetic study of adults with Cystic Fibrosis revealed a Cmax of 2.86 mg/L.<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>The maximum plasma concentration after administration of cysteamine eye drops is unknown, however, it is likely to be considerably lower than oral administration.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Products: Cystadrops (cysteamine solution 0.37%) for ophthalmic use" href="#reference-L15606">10</a></sup></p><p>According to prescribing information, the AUC 0-12 h for the delayed-release oral tablets is 99.26 ± 44.2 μmol*h/L with a Cmax of 27.70 ± 14.99 μmol/L.<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> </p><p>The AUC 0-12 for the immediate-release tablets is 192.00 ± 75.62 μmol*h/L with a Cmax of 37.72 ± 12.10 μmol/L.<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></p>