CYCLOSET
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 269.3 |
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 | Weight loss not recommended; limited human data, animal studies show risks. |
| 2nd trimester | Avoid; weight loss can harm fetus due to maternal starvation effects. |
| 3rd trimester | Avoid; risk of fetal harm outweighs benefits. |
Clinical note
Comprehensive clinical and safety monograph for CYCLOSET (CYCLOSET).
| Placental transfer | Cycloset is believed to cross the placenta based on molecular weight (269 Da) and animal data; specific human studies not available. |
| Breastfeeding | Excretion into human milk unknown; potential for serious adverse reactions in nursing infants, including hypoglycemia and sympathomimetic effects. Decision to discontinue drug or nursing should be based on importance of drug to mother. |
| Lactation Rating | L4 - Possibly Hazardous |
| 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. |
| Fertility Effects | No known adverse effects on fertility; may improve ovulation in women with PCOS due to insulin sensitization. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to bromocriptine or any componentSyncopal migrainesPostpartum women with history of coronary artery disease or other severe cardiovascular conditionsPreeclampsia or eclampsiaUncontrolled hypertension
| 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. |
| Food/Dietary | Avoid alcohol and alcohol-containing products. No specific food interactions; take with or without food. Maintain adequate hydration. |
| Clinical Pearls | Monitor for hypoglycemia, especially in elderly patients or those with renal impairment. Cycloserine may accumulate in renal insufficiency; dose reduction is necessary if CrCl < 50 mL/min. Watch for neuropsychiatric effects (seizures, psychosis, depression) and discontinue if severe. Pyridoxine 50-100 mg daily is recommended to reduce neurotoxicity. Avoid alcohol due to increased seizure risk. |
| Patient Advice | Take exactly as prescribed; do not miss doses or double up. · Report any signs of rash, confusion, dizziness, or unusual behavior immediately. · Avoid alcohol completely while on this medication. · If you have kidney problems, your dose may need adjustment. · Take pyridoxine (vitamin B6) as directed to lower risk of side effects. · Do not drive or operate heavy machinery if you feel drowsy or dizzy. · Complete the full course of therapy even if you feel better. |
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