<p>Morphine has a half life of 2-3 hours.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Lotsch J: Pharmacokinetic-pharmacodynamic modeling of opioids. J Pain Symptom Manage. 2005 May;29(5 Suppl):S90-103. doi: 10.1016/j.jpainsymman.2005.01.012. (PubMed ID 15907650)" href="#reference-A176116">5</a></sup></p>