From Wikipedia: Paracetamol apparently might modulate the endogenous cannabinoid system in the brain through its metabolite, AM404, which appears to inhibit th

From Wikipedia: Paracetamol apparently might modulate the endogenous cannabinoid system in the brain through its metabolite, AM404, which appears to inhibit the reuptake of the endogenous cannabinoid/vanilloid anandamide by neurons, making it more available to reduce pain. AM404 also appears to be able to directly activate the TRPV1 (older name: vanilloid receptor), which also inhibits pain signals in the brain.[24]