Lophophine, also known as 3-methoxy-4,5-methylenedioxyphenethylamine (MMDPEA; 5-Methoxy-MDPEA), is a psychedelic and entactogen drug of the phenethylamine class. It is the α-demethylated homologue of MMDA, and is also closely related to mescaline.

Alexander Shulgin previously suggested that lophophine may be a natural constituent of Peyote due to it being the only logical chemical intermediate for the biosynthesis of several tetrahydroisoquinolines known to be present in the species. Subsequently, it was indeed shown to be a minor component of both Peyote and San Pedro.

Shulgin reports that lophophine is active in the dosage range of 150-250 mg. He states that at these doses, MMDPEA is very similar to mescaline in action, and that a peaceful elevation of mood, euphoria, enhancement of visual perception, and the generation of closed-eye mental imagery are all present. At dosages above 300 mg, visual distortions that resemble those of standard doses of mescaline are said to begin to appear. Shulgin also notes that in contrast to mescaline, lophophine causes little nausea or vomiting.