Changes in liver tests during 1-year treatment of patients with Type 2 diabetes with pioglitazone, metformin or gliclazide

Aims Patients with Type 2 diabetes are at increased risk of liver damage. Therefore, it is of particular importance to investigate the hepatic effects of drugs used to treat such patients. Methods Liver testing results performed in four 1-year, randomized, double-blind studies comparing effects of pioglitazone, metformin or a sulphonylurea, gliclazide, in the treatment of over 3700 patients with Type 2 diabetes have been analysed. Results Pioglitazone caused reductions in mean levels of hepatic enzymes of between 3 and 18%, whilst gliclazide caused small increases of between 3 and 13%. Metformin treatment showed either small mean increases or decreases. More patients receiving pioglitazone had liver tests within the normal range at the end of treatment (>= 87%) compared with patients receiving metformin (>= 80%) or gliclazide (>= 75%). Slightly fewer patients with pioglitazone than with comparators showed a large increase (> 3 upper limit of normal) in alanine aminotransferase levels at any time during treatment (pioglitazone 0.9%, metformin 1.9%, gliclazide 1.9%). Conclusions During pioglitazone treatment there is a reduction in liver enzyme levels. Although the mechanism of this effect is not clear, the results demonstrate potential beneficial effects on the liver during treatment of patients with Type 2 diabetes with pioglitazone.