Troglitazone is a thiazolidinedione antidiabetic agent that lowers blood glucose by improving target cell response to insulin. It has a unique mechanism of action that is dependent on the presence of insulin for activity. Troglitazone decreases hepatic glucose output and increases insulin dependent glucose disposal in skeletal muscle. Its mechanism of action is thought to involve binding to nuclear receptors (PPAR) that regulate the transcription of a number of insulin responsive genes critical for the control of glucose and lipid metabolism. Troglitazone is a ligand to both PPAR_ and PPAR_, with a highter affinity for PPAR_. The drug also contains an _-tocopheroyl moiety, potentially giving it vitamin E-like activity. Troglitazone has been shown to reduce inflammation, and is associated with a decrase in nuclear factor kappa-B (NF-_B) and a concomitant increase in its inhibitor (I_B). NF-_B is an important cellular transcription regulator for the immune response. Unlike sulfonylureas, troglitazone is not an insulin secretagogue.
Troglitazone is an oral antihyperglycemic agent which acts primarily by decreasing insulin resistance. Troglitazone is used in the management of type II diabetes (noninsulin-dependent diabetes mellitus (NIDDM) also known as adult-onset diabetes). It improves sensitivity to insulin in muscle and adipose tissue and inhibits hepatic gluconeogenesis. Troglitazone is not chemically or functionally related to either the sulfonylureas, the biguanides, or the g-glucosidase inhibitors. Troglitazone may be used concomitantly with a sulfonylurea or insulin to improve glycemic control.
A sulfate conjugate metabolite (Metabolite 1) and a quinone metabolite (Metabolite 3) have been detected in the plasma of healthy males. A glucuronide conjugate (Metabolite 2) has been detected in the urine and also in negligible amounts in the plasma. In healthy volunteers and in patients with type 2 diabetes, the steady-state concentration of Metabolite 1 is six to seven times that of troglitazone and Metabolite 3. In in vivo drug interaction studies, troglitazone has been shown to induce cytochrome P450 CYP3A4 at clinically relevant doses.