The manufacture of intermediates to make pharmaceuticals is one of the most diverse uses of methylamines. The reaction of monomethylamine and ethylene oxide creates two key intermediates: methyldiethanolamine (MDEA) and monomethylethanolamine (NMEA) (see Gas and Oil Treatment). MDEA is used to make analgesics with sedative and antispasmodic effects, such as meperidine.
MMA reacted with phosgene or carbon dioxide yields N,N'dimethylurea. This is used to make xanthine derivatives, such as caffeine and theophylline. The reaction of MMA and phenylsuccinic acid yields phensuximide, an anticonvulsant. N-benzyl-n-methylamine is used in pharmaceuticals. MMA is also used to make intermediates for chlordiazepoxide and lorazepam tranquilizers, nortryptylene antidepressant, isometheptene veterinary smooth muscle relaxant, iothalamic acid x-ray contrast medium, and levothyroxine.
Sympathomimetic drugs are made from MMA, such as adrenaline (amination of 3,4-dihydroxyphenyl chloromethyl ketone from pyrocatechol), ephidrine (reductive amination of phenylmethyl diketone), neosynephrine, vanedrine, and veritol.
Dimethylamine is used to make DMAE (see Water Treatment), which has many uses to produce pharmaceuticals. It is used to make antihistamines, such as pheniramine, chlorpheniramine, and diphenhydramine, for the symptomatic relief of allergies, such as hay fever. DMAE is also used in the synthesis of local anesthetics, such as amethocaine, procaine, and pontocaine.
Propoxyphene analgesic and doxepin antidepressant are made from DMA. Salicylates of both MMA and DMA are used as ointments for skin disorders. DMA is used to make intermediates for tranquilizing agents.