The Pentagon is moving to limit off-label use of powerful anti-psychotic drugs for post-traumatic stress disorder — a practice some say may contribute to accidental drug overdoses among troops.

Assistant Secretary of Defense for Health Affairs Dr. Jonathan Woodson sent a letter to the services in February asking military treatment facilities to monitor prescriptions of atypical antipsychotics like risperidone and quetiapine, marketed under the brand name Seroquel.

The drugs, used to treat severe mental illnesses like schizophrenia and bipolar disorder, are sometimes prescribed to troops in lower doses to alleviate symptoms associated with PTSD and anxiety, including nightmares and irritability.

But when mixed with other prescriptions, they can be dangerous and sometimes fatal.

The Food and Drug Administration in 2011 added a warning label to quetiapine, saying its use with some synthetic opiates, including methadone, can increase the risk of a heart-stopping overdose.