CYSTADROPS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYSTADROPS (CYSTADROPS).
Cysteamine depletes cystine within lysosomes by forming a cysteine-cysteamine mixed disulfide that exits via the lysosomal cystine transporter, reducing cystine accumulation in cystinosis.
| Metabolism | Metabolized to cysteine and other metabolites; not extensively metabolized by CYP450 enzymes. |
| Excretion | Primarily renal as unchanged drug. Approximately 90% of the administered dose is excreted unchanged in urine within 24 hours. Biliary/fecal elimination is negligible (<5%). |
| Half-life | Terminal elimination half-life is approximately 5 hours. No significant accumulation with twice-daily dosing in patients with normal renal function. |
| Protein binding | Negligible (<10%); not bound to plasma proteins to any significant extent. |
| Volume of Distribution | 0.3 L/kg, indicating distribution primarily in extracellular fluid. |
| Bioavailability | Ophthalmic: systemic bioavailability is low (<10%) due to local administration and limited ocular absorption. Oral bioavailability not applicable; drug is not administered orally. |
| Onset of Action | Ophthalmic administration: reduction in corneal cystine crystal deposition observed within 1-2 months of continuous therapy. |
| Duration of Action | Sustained effect with continued dosing; crystals regrow if therapy is interrupted. Clinical benefit requires continuous long-term administration. |
Cystadrops (cysteamine hydrochloride) ophthalmic solution: 1 drop in each eye every 4 hours during waking hours.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for renal impairment; drug is administered topically and systemic absorption is negligible. |
| Liver impairment | No dose adjustment required for hepatic impairment; systemic exposure is minimal after topical administration. |
| Pediatric use | Same as adult dosing: 1 drop in each eye every 4 hours during waking hours. No weight-based modifications are needed for topical ophthalmic use. |
| Geriatric use | No specific dose adjustment required; use same dosing as adults. Monitor for tolerability as elderly patients may have reduced tear production or ocular surface issues. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYSTADROPS (CYSTADROPS).
| Breastfeeding | Systemic absorption of cysteamine from Cystadrops is negligible; transfer into breast milk is unlikely. However, no human data available; caution advised. M/P ratio not determined. |
| Teratogenic Risk | Cystadrops (cysteamine hydrochloride ophthalmic solution) is not absorbed systemically in significant amounts after ocular administration; therefore, teratogenic risk is minimal. However, animal studies with oral cysteamine show fetal adverse effects at high doses. No sufficient human data for ocular use. Risk cannot be excluded; use only if clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to cysteamine or any component of the formulation."]
| Precautions | ["Hypersensitivity reactions; patients should not drive or operate machinery if vision is blurred after instillation.","May cause ocular irritation or photosensitivity.","Use during pregnancy only if clearly needed."] |
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| Fetal Monitoring |
| No specific monitoring required due to minimal systemic absorption. Routine ophthalmologic monitoring for local adverse effects. In pregnant women, monitor for corneal changes and cystine crystal deposition. |
| Fertility Effects | No human data on fertility effects with ocular cysteamine. Animal studies with oral cysteamine showed impairment of fertility at high doses. Not expected to affect fertility via ocular route due to negligible systemic exposure. |