05:49 PM CDT on Wednesday, July 5, 2006

By JANET ST. JAMES / WFAA-TV

AP

Andrea Yates

Andrea Yates' treatment for post-partum depression played a big role in her first murder trial. Now the pills she was prescribed for depression may be the key in her second defense.

The FDA in November quietly ordered a safety labeling change for Effexor XR, a warning that in rare cases patients will experience "homicidal" thoughts.

Harris HEB psychiatrist Cathal Grant has been treating patients for depression for over 20 years.

He says many doctors probably don't know the warning has been added to Effexor. But this extreme side-effect doesn't surprise him either.

"Anyone who's suffered from severe depression will know that it can cause anger and irritability at times, and there are a certain percentage of those people who may be homicidal," said Dr. Grant.

Most anti-depressants do warn of side - effects including suicidal thoughts, hostility, aggressiveness, and manic reactions. Homicidal thoughts are not on any other anti-depressant labels, we could find.

Still, the vast majority of people take the medicine safely. Defense attorneys will no doubt argue Effexor's new labeling could prove Andrea Yates did not.

E-mail jst.james@wfaa.com.