Dopamine Agonists (Cycloset)

Reviewed by: HU Medical Review Board | Last reviewed: August 2023

Dopamine agonists are a class of drugs used to treat type 2 diabetes (T2D). They were first designed to treat other health conditions. But they also lower blood sugar for people with T2D, when combined with diet and exercise.

The only dopamine agonist approved to treat T2D is Cycloset® (bromocriptine). Your doctor may suggest Cycloset if other treatments do not work well. Talk to your doctor about the risks and benefits of dopamine agonists.

How do dopamine agonists work?

Dopamine agonists work by binding to proteins called “dopamine receptors.” Dopamine receptors control:1-3

  • Memory
  • Learning
  • Motor control
  • Other body processes

Abnormal dopamine receptor activity can lead to certain chronic health conditions. Dopamine agonists are common treatments for these conditions.1-3

We do not know how dopamine agonists work to treat T2D. In T2D, the pancreas does not produce enough insulin. Or, the body does not use insulin well. Insulin helps remove sugar from the bloodstream. This is why people with T2D often have high blood sugar.2

Dopamine receptors in the brain and pancreas control blood glucose levels. Dopamine agonists seem to reduce blood sugar. They may do this by:4-6

  • Reducing glucose production by the liver
  • Improving how the body uses insulin (increasing insulin sensitivity)


The only dopamine agonist approved to treat T2D is Cycloset® (bromocriptine). Dostinex® (cabergoline) is another dopamine agonist that has been studied in T2D. But it has not yet been approved to treat T2D.7

What are the possible side effects?

Side effects can vary. The most common side effects of dopamine agonists include:7

  • Nausea
  • Vomiting
  • Dizziness
  • Headache
  • Weakness and lack of energy
  • Low blood sugar

More serious side effects are rare, but possible. These include:7

  • Low blood pressure
  • Fainting
  • Drowsiness
  • Severe dizziness

These are not all the possible side effects of dopamine agonists. Talk to your doctor about what to expect when taking dopamine agonists. You also should call your doctor if you have any changes that concern you when taking dopamine agonists.

Other things to know

Before beginning treatment for T2D, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.

Take dopamine agonists as your doctor prescribes. They are usually taken as a tablet by mouth. Taking them with food can reduce the risk of side effects.7

When taking dopamine agonists, maintain a healthy diet and routine exercise. Your doctor may suggest combining dopamine agonists with other treatments. For example, the combination of Cycloset and metformin is more effective than either treatment alone.1

Before taking dopamine agonists, talk to your doctor about your full medical history. Certain medicines and medical conditions increase the risk of side effects. Tell your doctor about:7

  • Your other medical conditions, especially migraine headaches or mental health conditions
  • Any history of passing out or fainting
  • Any history of low blood pressure
  • Any allergies
  • Plans for pregnancy or breastfeeding
  • Other drugs you take, including over-the-counter drugs and supplements

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