Biguanides and thiazolidinediones are medications primarily used to treat type 2 diabetes mellitus. Type 2 diabetes is characterized by insulin resistance, which is when tissue cells have trouble responding to insulin in order to use glucose from the blood.
As a result, tissue cells starve for energy despite having high blood glucose levels, which is called hyperglycemia.
Now, the most commonly used biguanide is metformin, whereas commonly used thiazolidinediones are medications that end with the suffix -glitazone, like pioglitazone and rosiglitazone. These medications can be taken orally.
Once administered, they decrease insulin resistance by increasing insulin sensitivity, and thus, the uptake of glucose by muscle and fat cells.
In addition, these medications inhibit gluconeogenesis, or glucose production in the liver. The combination of these two mechanisms ultimately leads to a decrease in blood glucose.
Alright, now the good news about biguanides and thiazolidinediones is that they never cause hypoglycemia when used alone as monotherapy.
However, both groups have several other side effects. Clients taking biguanides can often present with gastrointestinal disturbances, such as anorexia, nausea, vomiting, and diarrhea.
In addition, they might experience dizziness, fatigue, and a characteristic bitter or metallic taste. As a boxed warning, biguanides can lead to lactic acidosis, which can be a life-threatening complication.