Recent research has identified heightened sensitivity to social rejection as a core feature of BPD. Rejection sensitivity can trigger the aggressive, impulsive, and self-injurious behaviors characteristic of the disorder.

Therefore targeting therapy towards the reduction of rejection sensitivity may improve the low rates of effectiveness of current pharmacological and behavioral therapies. Therefore, this proposal tests a theoretically-based pharmacological approach that specifically targets the heightened sensitivity to rejection experienced by BPD patients.

In prior research with normal controls, it was shown that chronic treatment with the physical pain-killer acetaminophen (e.g. Tylenol) reduced both neural responses to social rejection (using fMRI) as well as self-reported feelings of rejection in a daily diary study.

It is the aim of this research project to determine if the over-the-counter analgesic, acetaminophen (active ingredient in Tylenol), can reduce symptoms and behaviors in BPD patients. The goal of this proposal is to use an open-label design to determine if acetaminophen improves symptoms in BPD patients.

Inclusion Criteria:

• clinical diagnosis of borderline personality disorder
• 18 years or older
• if on psychiatric medication, must be on a stable dose
• able to swallow tablets

Exclusion Criteria:

• current, primary substance abuse, particularly alcoholism
• current eating disorder
• history or current psychotic disorder
• suicidal ideation or behavior requiring imminent inpatient treatment
• pregnancy
• Participants whose medication has not been stable for more than 4 weeks
• Impaired liver function (> 1.25x the upper limit of the reference range)
• Conditions that can affect immune system functioning.