OBJECTIVE: This study examined the effect of adjunctive telmisartan on body metabolism in clozapine- or olanzapine-treated patients with schizophrenia. METHOD: Each subject had been on stable dose of olanzapine or clozapine for at least 1 month. In a 12-week randomized, double-blind, placebo-controlled study, subjects received either telmisartan (80 mg once per day) or placebo. The homeostasis model of assessment of insulin resistance (HOMA-IR) was calculated based on fasting blood levels of insulin and glucose. Fasting blood levels of triglycerides and cholesterols, as well as serum levels of high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) were measured. The whole-body dual-energy X-ray absorptiometry (DXA) was used to assess body composition. Lipid particles were assessed using nuclear magnetic resonance (NMR) spectroscopy. All assessments were conducted at baseline and repeated at week 12. RESULTS: Fifty-four subjects were randomized and 43 completed the study (22 in the telmisartan group, 21 in the placebo group). There were no significant differences between the two groups in week 12 changes for HOMA-IR or fasting triglycerides (- 0.18 +/- 1.24 vs 0.39 +/- 1.39, p = 0.181; - 26 +/- 76 vs - 10 +/- 81 mg/dL, p = 0.679, respectively) (telmisartan vs placebo). Further, there were no significant between group differences in week 12 changes for other fasting lipids, body weight, body mass index, waist circumference, as well as various measures of lipid particles (p's > 0.100). The DXA assessment showed no significant differences between the two groups in week 12 changes for fat mass, lean mass, or total mass (p's > 0.100). CONCLUSION: In the present study, adjunctive treatment of telmisartan did not seem to improve body metabolism in schizophrenia patients receiving olanzapine or clozapine. The implications for future studies were discussed. CLINICALTRIALS. GOV IDENTIFIER: NCT00981526.