Although the research paper linked to by GerryW is behind a paywall, a couple of earlier papers are available for either a small charge [1], or no charge [2].

[1] The pharmacology of palmitoylethanolamide and first data on the therapeutic efficacy of some of its new formulations. Petrosino S, Di Marzo V. British journal of pharmacology, 29 September 2016 (Early View), doi: 10.1111/bph.13580.

(It's behind a paywall, but you can preview the first page for free. If you then register as a patient or carer (patientACCESS), you should be able to buy the full article for just a few dollars. However, the link titled "access" wasn't working when I tried it.)

The pharmacology of palmitoylethanolamide and first data on the therapeutic efficacy of some of its new formulations - Petrosino - 216 - British Journal of Pharmacology - Wiley Online Library

[2] Palmitoylethanolamide, a naturally occurring lipid, is an orally effective intestinal anti-inflammatory agent. Borrelli F, Romano B, Petrosino S, Pagano E, Capasso R, Coppola D, Battista G, Orlando P, Di Marzo V, Izzo AA. British journal of pharmacology, Volume 172, Issue 1, January 2015, doi: 10.1111/bph.12907.

(This one is free.)

Palmitoylethanolamide, a naturally occurring lipid, is an orally effective intestinal anti-inflammatory agent