Is Mounjaro a Sulfonylurea? No, Plus Hypoglycemia Risk

What kind of drug is Mounjaro?

Mounjaro is tirzepatide, a single peptide that activates both the GIP receptor and the GLP-1 receptor. The FDA label describes it as a glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist [1]. It is injected under the skin once a week. Mounjaro starts at 2.5 mg weekly. If more glycemic control is needed, the dose may be increased in 2.5 mg steps after at least 4 weeks at the current dose, to a maximum of 15 mg weekly in adults and 10 mg weekly in children 10 and older [1].

Sulfonylureas are a separate class of insulin secretagogues, which the label uses as its example in the hypoglycemia warning [1]. Mounjaro is not one of them and is not an oral tablet.

Mounjaro's approved uses are type 2 diabetes in adults and children 10 and older, and reducing the risk of major cardiovascular events in adults with type 2 diabetes who are at high risk for them. Its label does not list weight loss as an indication [1].

How does Mounjaro lower blood glucose?

Tirzepatide increases insulin secretion in a glucose-dependent way, reduces glucagon, and increases insulin sensitivity [1].

The label's hypoglycemia warning is not about Mounjaro alone. It is titled "Hypoglycemia with Concomitant Use of Insulin Secretagogues or Insulin" and states that patients receiving Mounjaro with an insulin secretagogue (for example a sulfonylurea) or with insulin may have an increased risk of hypoglycemia, including severe hypoglycemia [1].

What does the label say about the companion drug?

The warning says the risk of hypoglycemia may be lowered by a reduction in the dose of the sulfonylurea (or other insulin secretagogue) or of insulin, and tells prescribers to inform patients using these medications of the risk and educate them on the signs and symptoms of hypoglycemia [1]. The drug interactions section adds that when initiating Mounjaro, a prescriber should consider reducing the dose of concomitant insulin secretagogues or insulin to reduce the risk of hypoglycemia [1]. Neither section gives a specific percentage reduction.