<p>Morphine is absorbed in the alkaline environments of the upper intestine and rectal mucosa.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Hoskin PJ, Hanks GW: Morphine: pharmacokinetics and clinical practice. Br J Cancer. 1990 Nov;62(5):705-7. (PubMed ID 2245160)" href="#reference-A176119">6</a></sup> The bioavailability of morphine is 80-100%.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Stuart-Harris R, Joel SP, McDonald P, Currow D, Slevin ML: The pharmacokinetics of morphine and morphine glucuronide metabolites after subcutaneous bolus injection and subcutaneous infusion of morphine. Br J Clin Pharmacol. 2000 Mar;49(3):207-14. (PubMed ID 10718775)" href="#reference-A176164">8</a></sup> There is significant first-pass metabolism, therefore oral doses are 6 times larger than parenteral doses to achieve the same effect. Morphine reaches steady-state concentrations after 24-48 hours.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Pacifici GM: Metabolism and pharmacokinetics of morphine in neonates: A review. Clinics (Sao Paulo). 2016 Aug;71(8):474-80. doi: 10.6061/clinics/2016(08)11. (PubMed ID 27626479)" href="#reference-A176035">1</a></sup> Parenteral morphine has a T<sub>max</sub> of 15 minutes and oral morphine has a T<sub>max</sub> of 90 minutes, with a C<sub>max</sub> of 283nmol/L.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Glare PA, Walsh TD: Clinical pharmacokinetics of morphine. Ther Drug Monit. 1991 Jan;13(1):1-23. (PubMed ID 2057987)" href="#reference-A176122">7</a>,<a class="reference-popover-link" data-content="Stuart-Harris R, Joel SP, McDonald P, Currow D, Slevin ML: The pharmacokinetics of morphine and morphine glucuronide metabolites after subcutaneous bolus injection and subcutaneous infusion of morphine. Br J Clin Pharmacol. 2000 Mar;49(3):207-14. (PubMed ID 10718775)" href="#reference-A176164">8</a></sup> The AUC of morphine is 225-290nmol*h/L.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Stuart-Harris R, Joel SP, McDonald P, Currow D, Slevin ML: The pharmacokinetics of morphine and morphine glucuronide metabolites after subcutaneous bolus injection and subcutaneous infusion of morphine. Br J Clin Pharmacol. 2000 Mar;49(3):207-14. (PubMed ID 10718775)" href="#reference-A176164">8</a></sup></p>