Circadin Side Effects

Circadin is a type of prescription medication that contains melatonin and is used to induce drowsiness in patients over the age of 55 who have insomnia, a sleep disorder. Melatonin is a sleep-regulating hormone that occurs naturally within the body. Circadin is marketed within Europe and Israel but is not available in the United States. Patients taking Circadin should discuss the potential side effects of this medication with a doctor before beginning treatment.

Circadin is a medication used to treat insomnia. (Image: klebercordeiro/iStock/Getty Images)

Mood Changes

While receiving treatment with Circadin, patients can experience unusual mood-related changes as a side effect. Patients can begin to feel abnormally irritable, restless or nervous and may become fidgety or hyperactive during treatment. These side effects are temporary but may persist for the duration of Circadin use.

Sleep Difficulties or Abnormal Dreams

Patients taking Circadin can experience sleep difficulties as a side effect of treatment. Insomnia symptoms may persist in certain patients, while other patients may experience increased drowsiness or fatigue throughout the day, explain health officials at the European Medicines Agency. Abnormal, vivid dreams can also cause patients to wake frequently throughout the night and can contribute to side effects of increased daytime tiredness. Sensations of dizziness that arise as a side effect of Circadin can affect a patient's ability to walk or stand normally. Patients should only take Circadin before bedtime and should avoid participating in potentially hazardous activities, such as driving a car, immediately after taking this medication.

Flu-like Symptoms

Treatment with Circadin can lead to the emergence of flu-like symptoms in certain patients. These flu-like side effects can include headache, sore throat, weakness, body aches or sweating, explains NetDoctor, a health and wellness website supported by physicians and nurses in the United Kingdom. Patients experiencing any of these side effects should contact a doctor for further evaluation and care.

Stomach Upset or Weight Gain

Circadin treatment can cause stomach-related side effects in certain patients. Stomach pain or constipation can develop, which may occur in conjunction with vomiting or abdominal gas or bloating. A dry or sticky sensation within the mouth may cause increased thirst or sore throat in affected patients. Certain patients may also experience unintended weight gain as a side effect of Circadin treatment even if no changes have been made to diet or exercise routines.


Treatment with Circadin can cause bile, a yellow-colored digestive substance produced by the liver, to accumulate within the blood. If this occurs, patients can develop jaundice, a condition characterized by yellowing of the skin or eyes, explains the European Medicines Agency.

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