Cycloserine is an oral broad spectrum antibiotic effective against tuberculosis, by inhibiting cell wall synthesis of TB bacilli at early stage of peptidoglycan synthesis. For the treatment against tuberculosis, it is classified as a second line drug.

It is also being trialed for treatment of phobias as well as an adjuvant to conventional treatments for depression, obsessive-compulsive disorder and schizophrenia.

The side effects are mainly CNS manifestations i.e. headache, irritability, depression, convulsions. Co-administration of pyridoxine can reduce the incidence of some of the CNS side effects(e.g. convulsions).

These psychotropic responses are related to D-cycloserine's action as a partial agonist of the neuronal NMDA receptor for glutamate and have been examined in implications with sensory-related fear extinction in the amygdala. See Michael Davis, Barbara Rothbaum, Kerry Ressler et al. and their work with PTSD at Emory University's School of Medicine.