CYCLOSET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLOSET (CYCLOSET).
Cycloset (bromocriptine mesylate) is a dopamine D2 receptor agonist. It improves glycemic control in type 2 diabetes by resetting hypothalamic circadian rhythms, thereby reducing hepatic glucose production and increasing insulin sensitivity. It also suppresses the release of very low-density lipoprotein from the liver.
| Metabolism | Primarily hepatic via cytochrome P450 3A4 (CYP3A4). Inactive metabolites are excreted mainly in feces (80%) and urine (2-10% unchanged). |
| Excretion | Renal: ~90% (30% unchanged, rest as inactive metabolites); fecal: ~10%. |
| Half-life | Terminal elimination half-life is 4–6 hours in patients with normal renal function; clinically, steady-state is reached within 24 hours. |
| Protein binding | ~20–30% bound, primarily to albumin. |
| Volume of Distribution | 0.5–1.0 L/kg, indicating moderate distribution into tissues. |
| Bioavailability | Oral: ~65–75% due to first-pass metabolism. |
| Onset of Action | Oral: 60–90 minutes for prolactin reduction; peak effect on prolactin levels at 2–3 hours. |
| Duration of Action | Prolactin suppression lasts 8–12 hours after a single dose, requiring twice-daily dosing for sustained effect. |
1.6 mg to 2.4 mg administered orally once daily at bedtime. Titrate by 0.8 mg every 2 weeks based on glycemic response and tolerability.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in patients with eGFR <30 mL/min/1.73 m2. For eGFR 30-50 mL/min/1.73 m2: maximum dose 0.8 mg daily. |
| Liver impairment | No dose adjustment required for mild hepatic impairment (Child-Pugh class A). Not recommended in moderate to severe hepatic impairment (Child-Pugh class B or C) due to lack of data. |
| Pediatric use | Not approved for pediatric patients. Safety and efficacy in patients <18 years have not been established. |
| Geriatric use | Start at 0.8 mg once daily; titrate slowly due to increased risk of orthostatic hypotension and hypoglycemia. Consider renal function and comorbidities. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYCLOSET (CYCLOSET).
| Breastfeeding | Not recommended; no data on excretion in human milk. M/P ratio unknown. |
| Teratogenic Risk | First trimester: insufficient human data; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: no known fetal risks; drug may cause maternal hypoglycemia which can affect fetus. |
| Fetal Monitoring | Monitor maternal blood glucose, hemoglobin A1c, and fetal growth via ultrasound. Assess for maternal hypoglycemia. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to bromocriptine or any component of the formulation.","Concomitant use with CYP3A4 inducers (e.g., rifampin, anticonvulsants) or inhibitors (e.g., azole antifungals, macrolide antibiotics).","Severe ischemic heart disease or peripheral vascular disorders.","Syncopal migraine or history of myocardial infarction with residual arrhythmias.","Uncontrolled hypertension.","Lactation: inhibits lactation, do not use in women with pregnancy or nursing unless essential."]
| Precautions | ["Risk of hypotension, especially at initiation of therapy; monitor blood pressure.","May cause somnolence and dizziness; advise patients not to drive or operate machinery until effects are known.","Use with caution in patients with cardiovascular disease, especially those with angina or recent myocardial infarction.","May exacerbate psychotic disorders; use caution in patients with a history of psychosis.","Fibrotic complications (pulmonary, pericardial, retroperitoneal fibrosis) have been reported with ergot-derived dopamine agonists; monitor for symptoms.","Discontinue if signs of cardiac valvulopathy occur."] |
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| Fertility Effects | No known adverse effects on fertility; may improve ovulation in women with PCOS due to insulin sensitization. |