<p>Due to its extensive metabolism, only 2% to 4% of the unchanged drug can be detected in the urine.<sup class="text-reference-group"><a class="reference-popover-link" data-content="CARDIZEM® LA (diltiazem hydrochloride) extended-release tablets - FDA Label" href="#reference-L10556">12</a></sup> The major urinary metabolite in healthy volunnteers was N-monodesmethyl diltiazem, followed by deacetyl N,O-didesmethyl diltiazem, deacetyl N-monodesmethyl diltiazem, and deacetyl diltiazem; however, there seems to be large inter-individual variability in the urinary excretion of DTZ and its metabolites.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Yeung PK, Prescott C, Haddad C, Montague TJ, McGregor C, Quilliam MA, Xei M, Li R, Farmer P, Klassen GA: Pharmacokinetics and metabolism of diltiazem in healthy males and females following a single oral dose. Eur J Drug Metab Pharmacokinet. 1993 Apr-Jun;18(2):199-206. doi: 10.1007/BF03188796. (PubMed ID 8243504)" href="#reference-A178516">6</a></sup></p>