['Olanzapine (OLZ) is known to cause weight gain and metabolic disturbances, which may have serious implications with respect to medical comorbidities such as metabolic syndrome and insulin resistance.', 'The aim of this study was to evaluate the effects of two angiotensin II type 1 receptor blockers (ARBs) which are widely used as antihypertensive agents, valsartan (VAL) and telmisartan (TEL), on insulin resistance in patients with schizophrenia treated with OLZ.', 'Thirty inpatients with schizophrenia with OLZ monotherapy over 8 weeks participated in this study. To assess insulin resistance, the homeostasis model assessment of insulin resistance (HOMA-IR), fasting plasma glucose (PG) levels and immunoreactive insulin (IRI) levels were measured [HOMA-IR = fasting PG level (mmol/L) x fasting IRI level (μU/ml)/22.5]. VAL add-on treatment was performed in insulin-resistant patients (HOMA-IR\u2009>\u20091.6) for 12 weeks. After a 12-week VAL washout period, TEL add-on treatment was carried out for 12 weeks. The effects of ARBs on insulin resistance and other metabolic variables were assessed.', 'In all 30 patients, both body mass index and abdominal circumference were strongly correlated with HOMA-IR. Twelve patients showed high HOMA-IR and were deemed to be insulin resistant. Add-on therapy of VAL and TEL resulted in a significant decrease in fasting IRI levels and HOMA-IR. No differences in any effects were observed between VAL and TEL. No adverse effects of either ARBs were observed in this study.'] Do angiotensin II type 1 receptor blockers improve insulin sensitivity in patients with schizophrenia being treated with olanzapine?