<p>When administered vaginally, progesterone is well absorbed by uterine endometrial tissue, and a small percentage is distributed into the systemic circulation.
The amount of progesterone in the systemic circulation appears to be of minimal importance, especially when implantation, pregnancy, and live birth outcomes appear similar for intramuscular and vaginal administration of progesterone <sup class="text-reference-group"><a class="reference-popover-link" data-content="Paulson RJ, Collins MG, Yankov VI: Progesterone pharmacokinetics and pharmacodynamics with 3 dosages and 2 regimens of an effervescent micronized progesterone vaginal insert. J Clin Endocrinol Metab. 2014 Nov;99(11):4241-9. doi: 10.1210/jc.2013-3937. Epub 2014 Feb 25. (PubMed ID 24606090)" href="#reference-A175657">11</a></sup>. </p>