The three most serious side effects of Cycloset are low blood pressure (hypotension), psychotic symptoms, and somnolence (drowsiness).
Hypotension can cause lightheadedness and fainting (syncope). This symptom is generally seen in patients who are also taking a medication to treat high blood pressure. In trials, this side effect was rare, occurring in less than 2% of patients (less than 1% after subtracting the incidence in placebo patients).
Psychosis is a serious mental condition in which a person loses touch with reality. It may involve hallucinations (sensing things that are not there, such as hearing voices) or delusions (firmly held, obviously false beliefs). Cycloset is not recommended for patients already suffering from a psychotic disorder such as schizophrenia. In trials, Cycloset has not been reported to have caused psychotic symptoms in any patients, but the warning remains because the active ingredient bromocriptine is associated with psychosis.
Somnolence resulting from Cycloset usually improves with time. Patients taking this medication should refrain from driving or operating heavy machinery after each Cycloset dosage increase until they know how the medication affects them.
The most common side effect of Cycloset is nausea, occurring in about one fourth of patients. Taking Cycloset with food may reduce this symptom. Other reported side effects are nose and sinus irritation, asthenia (weakness), dizziness, and amblyopia (decreased vision in one eye, or "lazy eye"). Cycloset is a dopamine agonist (i.e. it increases the activity of the neurotransmitter dopamine), and should usually not be combined with other dopamine agonists or with antipsychotics (which reduce dopamine activity).
