Inability to obtain patients

Approximately one third of patients with schizophrenia show a poor response to standard treatment with antipsychotic medications. This treatment resistant group of patients represents a major challenge in everyday psychiatry, and consumes a disproportionate amount of time from the clinicians, resulting in considerable costs to the society and government. Anecdotal evidence suggests that the enzyme dipeptidyl peptidase IV (DPPIV) may be altered in patients with schizophrenia, with a higher level DPPIV enzyme activity being noted. We postulate that this may play a role in the neuropathology of schizophrenia patients and by inhibiting the DPPIV enzyme activity with a DPPIV inhibitor such as linagliptin, we will be able to improve and even ameliorate the symptoms of schizophrenic patients. However, until now there have yet any studies on the potential of these inhibitors in schizophrenia patients. A pilot study is thus proposed to evaluate the potential of the DPPIV inhibitor, linagliptin as an adjunct in schizophrenia patients who are non-responsive to treatment, which will establish the feasibility of a larger trial.

Inclusion Criteria:

• 18 years of age and above
• Diagnosis of schizophrenia.
• Clinically stable antipsychotic regimen for the last 3 months
• A total score of 80 or greater at baseline on the Positive and Negative Syndrome Scale
• Competent and willing to provide written, informed consent

Exclusion Criteria:

• History of substance dependence within the past 2 months
• Existing relevant physical health problems: such as uncontrolled cardiovascular disease and impaired liver/ renal function
• History of diabetes
• History of hepatic or biliary diseases / biliary obstruction
• A serious suicide/homicide risk in the opinion of the investigator
• Known allergy to linagliptin