CYSTARAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYSTARAN (CYSTARAN).
Cystaran (cysteamine ophthalmic solution) acts by depleting cystine within corneal epithelial cells. Cysteamine reduces cystine accumulation by converting cystine to cysteine, which is then transported out of lysosomes via the cysteine transporter. This lowers corneal cystine crystal deposition in cystinosis patients.
| Metabolism | Cysteamine is extensively metabolized in the liver and extrahepatic tissues. The primary metabolic pathway involves oxidation to taurine and sulfate via cysteine dioxygenase and subsequent enzymes. Minor pathways include acetylation and transamination. |
| Excretion | Renal (primarily as unchanged drug); approximately 67% of a dose is excreted unchanged in urine within 24 hours. Biliary/fecal elimination is negligible (<2%). |
| Half-life | Terminal elimination half-life is approximately 3.3 hours in adults with normal renal function. Clinically, this supports twice-daily dosing for ophthalmic use, as systemic accumulation is not significant. |
| Protein binding | Approximately 10% bound to plasma proteins (primarily albumin), indicating minimal binding. |
| Volume of Distribution | Approximately 0.33 L/kg, suggesting distribution primarily into extracellular fluid and limited tissue penetration, consistent with its small molecular size and hydrophilic nature. |
| Bioavailability | Topical ophthalmic: Systemic bioavailability is negligible due to ocular administration and low absorption; less than 1% of a topical dose reaches systemic circulation. |
| Onset of Action | Topical ophthalmic: Symptomatic relief of corneal cystine crystal deposition may be observed within weeks to months of therapy. Maximum reduction of crystal density typically requires months of treatment. |
| Duration of Action | Topical ophthalmic: Duration of action is dependent on adherence; continuous twice-daily dosing is required to maintain reduced corneal crystal burden. Discontinuation leads to gradual reaccumulation of crystals. |
Instill 1 drop in each eye every 4 hours while awake.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established. |
| Geriatric use | No dose adjustment required; caution with concurrent nephrotoxic agents. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYSTARAN (CYSTARAN).
| Breastfeeding | No data on excretion in human milk after topical administration. Systemic absorption is minimal; risk to nursing infant is likely low. M/P ratio not available. |
| Teratogenic Risk | Cystaran (cysteamine ophthalmic solution) is administered topically and systemic absorption is minimal. No human data on fetal risk. Animal studies with oral cysteamine show adverse effects at high doses, but topical exposure is negligible. Risk cannot be excluded; use if benefit outweighs potential risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to cysteamine or any component of the formulation"]
| Precautions | ["Ocular toxicity: May cause eye pain, irritation, and corneal edema; monitor for visual disturbances.","Hypersensitivity reactions: Discontinue if signs of allergy occur.","Use with caution in patients with hepatic impairment due to potential for increased systemic exposure."] |
Loading safety data…
| No specific monitoring required beyond routine pregnancy care. If systemic effects suspected (unlikely), monitor for growth and development. |
| Fertility Effects | No known effects on fertility from topical ophthalmic use. Oral cysteamine in animal studies showed impaired fertility at high doses; relevance to topical route is negligible. |