Arecaidine propargyl ester is an agonist of M2 muscarinic acetylcholine receptors (mAChRs). It selectively binds to M2 over M1, M3, M4, and M5 mAChRs in CHO cells expressing the human receptors (Kis = 0.0871, 1.23, 0.851, 0.977, and 0.933 µM, respectively). Arecaidine propargyl ester induces contractions in isolated guinea pig atrium (pD2 = 8.67). It induces apoptosis and the production of reactive oxygen species (ROS) in U87 and U251 glioblastoma cells when used at a concentration of 100 µM. Arecaidine propargyl ester decreases mean arterial blood pressure in normotensive cats (ED25 = 1.9 nmol/kg). It is toxic to house flies (Musca) when administered at a dose of 75 µg/fly.