CYSTADANE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYSTADANE (CYSTADANE).
Betaine acts as a methyl group donor in the remethylation of homocysteine to methionine, a reaction catalyzed by betaine-homocysteine methyltransferase. This reduces elevated homocysteine levels in homocystinuria.
| Metabolism | Betaine is not significantly metabolized; it is excreted unchanged in urine. |
| Excretion | Renal excretion of unchanged betaine accounts for less than 5% of the administered dose; metabolism occurs via demethylation to dimethylglycine, which is further metabolized to sarcosine and glycine. Metabolites are excreted renally. A small fraction may be eliminated in feces. |
| Half-life | Cystadane (betaine anhydrous) has a terminal elimination half-life of approximately 14 hours (range 10-18 hours) following oral administration, supporting twice-daily dosing. The half-life is prolonged in patients with renal impairment. |
| Protein binding | Betaine is not significantly bound to plasma proteins (<10% bound). |
| Volume of Distribution | The apparent volume of distribution (Vd/F) is approximately 1.0 L/kg, indicating distribution into total body water. Clinical significance: extensive distribution into tissues, including the central nervous system. |
| Bioavailability | Oral bioavailability is high, estimated at >90% based on absorption and urinary recovery of metabolites. Betaine is rapidly and completely absorbed from the gastrointestinal tract. |
| Onset of Action | Oral administration: Reduction in plasma homocysteine levels typically occurs within days to weeks; however, clinical response (e.g., prevention of vascular events) may require longer treatment. Initial biochemical effects can be observed after 1-2 weeks. |
| Duration of Action | The reduction in homocysteine levels persists for the dosing interval (12 hours) with twice-daily dosing; continuous therapy is required to maintain homocysteine suppression. The effect diminishes within days to weeks after discontinuation. |
100 mg/kg/day orally divided into 3 doses, maximum 100 mg/kg/day; typical adult dose 6-9 g/day in divided doses.
| Dosage form | FOR SOLUTION |
| Renal impairment | No specific adjustment guidelines; use with caution in renal impairment due to betaine accumulation; monitor serum betaine levels if available. |
| Liver impairment | No specific adjustment required; not metabolized by liver. |
| Pediatric use | 100 mg/kg/day orally divided into 3 doses; maximum 100 mg/kg/day. |
| Geriatric use | No specific guidelines; start at low end of dosing range and adjust based on renal function and tolerance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYSTADANE (CYSTADANE).
| Breastfeeding | Betaine is naturally present in human breast milk. Exogenous betaine (Cystadane) is likely excreted into milk, but the amount is expected to be low relative to endogenous levels. M/P ratio not established. Considered compatible with breastfeeding given the low risk; however, caution is advised in infants with homocystinuria due to potential accumulation. Monitor infant for possible effects. |
| Teratogenic Risk | Betaine (Cystadane) is an amino acid derivative with no known teratogenic effects in humans. Animal studies have not shown fetal harm. However, adequate and well-controlled studies in pregnant women are lacking. Use during pregnancy only if clearly needed, considering potential benefits vs risks. First trimester: no known increased risk of major birth defects; second/third trimester: potential for maternal benefit with careful monitoring. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to betaine or any component of the formulation.
| Precautions | Monitor plasma methionine levels as hypermethioninemia may occur; use with caution in patients with renal impairment. |
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| Fetal Monitoring | Monitor maternal plasma homocysteine levels, methionine levels (avoid hypermethioninemia), and renal function. In pregnancy, assess fetal growth and development via ultrasound as clinically indicated. Monitor for maternal electrolyte imbalances (e.g., hypernatremia) due to betaine's osmotic effects. |
| Fertility Effects | No known adverse effects on fertility in males or females. Animal studies have not reported reproductive impairment. In humans, betaine is used for homocystinuria, which may itself affect fertility; treatment may improve reproductive outcomes. |