<p>The metabolites of diphenhydramine are conjugated with glycine and glutamine and excreted in urine <sup class="text-reference-group"><a class="reference-popover-link" data-content="Electronic Medicines Compendium: Boots Sleepeaze (diphenhydramine hydrochloride) 50mg Tablets Monograph" href="#reference-L5281">12</a>,<a class="reference-popover-link" data-content="Electronic Medicines Compendium: Nytol One-A-Night (diphenhydramine hydrochloride) Monograph" href="#reference-L5287">13</a></sup>. Only about 1% of a single dose is excreted unchanged in urine <sup class="text-reference-group"><a class="reference-popover-link" data-content="Electronic Medicines Compendium: Boots Sleepeaze (diphenhydramine hydrochloride) 50mg Tablets Monograph" href="#reference-L5281">12</a>,<a class="reference-popover-link" data-content="Electronic Medicines Compendium: Nytol One-A-Night (diphenhydramine hydrochloride) Monograph" href="#reference-L5287">13</a></sup>. The medication is ultimately eliminated by the kidneys slowly, mainly as inactive metabolites <sup class="text-reference-group"><a class="reference-popover-link" data-content="Electronic Medicines Compendium: Boots Sleepeaze (diphenhydramine hydrochloride) 50mg Tablets Monograph" href="#reference-L5281">12</a>,<a class="reference-popover-link" data-content="Electronic Medicines Compendium: Nytol One-A-Night (diphenhydramine hydrochloride) Monograph" href="#reference-L5287">13</a></sup>.</p>