Cysteamine Hydrochloride (Monograph)

Brand name: Cystaran
Drug class: EENT Drugs, Miscellaneous
- Anticystine Agents
- Cystine-depleting Agents
Chemical name: 2-Amino-ethanethiol
Molecular formula: C₂H₇NSC₂H₇NS•HCl
CAS number: 60-23-1

Introduction

Cystine-depleting agent; an aminothiol.

Uses for Cysteamine Hydrochloride

Corneal Cystine Crystal Accumulation

Treatment of corneal cystine crystal accumulation in patients with cystinosis (designated an orphan drug by FDA for this use).

Because oral cysteamine does not reverse corneal cystine crystal accumulation in cystinosis patients, concurrent ophthalmic cysteamine is necessary.

Temporarily reduces formation of corneal cystine crystals in patients with cystinosis; strict compliance and continued use are necessary for sustained efficacy.

Commercially available in US as a 0.44% (of cysteamine) ophthalmic solution that contains the preservative benzalkonium chloride (Cystaran). Various other ophthalmic formulations (e.g., 0.11%, 0.55%, preservative-free) were studied during the clinical trial program in the US.

Cysteamine Hydrochloride Dosage and Administration

General

Available only through a specialty pharmacy. Call the Cystaran Hotline at 800-440-0473 or visit [Web] for specific information.

Administration

Ophthalmic Administration

Apply topically to each eye as an ophthalmic solution; the solution is for topical ophthalmic use only.

To minimize risk of contamination, avoid touching the eyelids, surrounding areas of the eye, or any other surface with the dropper tip of the bottle. Keep the bottle tightly closed when not in use. (See Advice to Patients.)

Remove contact lenses prior to each dose (since the benzalkonium chloride preservative may be absorbed by soft lenses); may reinsert lenses 15 minutes following administration.

For proper storage information, see Storage under Stability and also see Advice to Patients.

Dosage

Available as cysteamine hydrochloride; dosage is expressed in terms of cysteamine.

Each 6.5 mg of cysteamine hydrochloride is equivalent to 4.4 mg of cysteamine.

Pediatric Patients

Corneal Cystine Crystal Accumulation

Ophthalmic

1 drop of a 0.44% solution in each eye every waking hour.

Continued therapy is necessary since corneal cystine crystals accumulate when therapy is discontinued.

Adults

Corneal Cystine Crystal Accumulation

Ophthalmic

1 drop of a 0.44% solution in each eye every waking hour.

Continued therapy is necessary since corneal cystine crystals accumulate when therapy is discontinued.

Special Populations

No special population dosage recommendations at this time. (See Renal Impairment under Cautions.)

Cautions for Cysteamine Hydrochloride

Contraindications

Manufacturer states none known.

Warnings/Precautions

Benign Intracranial Hypertension

Benign intracranial hypertension (or pseudotumor cerebri) and/or papilledema reported with oral cysteamine bitartrate therapy. Benign intracranial hypertension also reported with ophthalmic cysteamine, but all patients were concurrently receiving oral cysteamine therapy.

Specific Populations

Pregnancy

Category C.

Lactation

Not known whether oral cysteamine is distributed into human milk. Systemic exposure expected to be negligible following ophthalmic administration. Discontinue nursing or the drug.

Pediatric Use

Safety and efficacy established in pediatric patients; the drug is approved for use in such patients. The majority of patients in the ophthalmic cysteamine clinical trials were pediatric patients.

Geriatric Use

Not evaluated; the reduced life expectancy from cystinosis did not allow for inclusion of geriatric patients in the clinical study population.

Renal Impairment

Effect of renal impairment on the pharmacokinetics of cysteamine following ophthalmic administration not evaluated because ophthalmic exposure is negligible compared with systemic exposure. However, the majority of patients in the ophthalmic clinical studies were assumed to have had some degree of renal impairment due to their underlying disease. (See Special Populations under Dosage and Administration.)

Common Adverse Effects

Photophobia (sensitivity to light), ocular (including conjunctival) redness, ocular pain and/or irritation, headache, visual field defects.

Drug Interactions

No known drug interactions. Clinically important interactions with systemically-administered drugs unlikely because of cysteamine's negligible systemic exposure following topical ophthalmic application.

Cysteamine Hydrochloride Pharmacokinetics

Absorption

Bioavailability

Peak concentrations of cysteamine following topical ophthalmic application of the ophthalmic solution not known. Because the total daily ophthalmic dosage of cysteamine is <2% of the recommended daily oral dosage, systemic exposure following ophthalmic administration expected to be negligible.

Special Populations

Renal impairment: Pharmacokinetics not evaluated following ophthalmic administration.

Distribution

Extent

Following oral administration, not known whether distributed into human milk. Systemic exposure likely to be negligible following ophthalmic administration.

Stability

Storage

Ophthalmic

Solution

Store unopened bottles frozen at -25° to -15°C in original carton.

Thaw bottle completely for approximately 24 hours before use.

Store thawed bottle at 2–25°C for ≤1 week; discard bottle 1 week after thawing. Do not refreeze. (See Advice to Patients.)

Actions

Reacts with cystine within lysosomes to convert it to cysteine and cysteine-cysteamine mixed disulfides, which can pass through the lysosomal membrane, resulting in cystine depletion from the cell and a reduction of corneal cystine crystals.

Advice to Patients

Importance of advising patients and caregivers on proper storage of bottles containing cysteamine hydrochloride ophthalmic solution. Initially, store bottles in the freezer in their original carton; each week, remove one new bottle from the freezer and allow it to thaw completely (for approximately 24 hours) before use. After completely thawed, store bottle at 2–25°C (36–77°F); do not refreeze. Importance of noting the date the bottle was completely thawed in the space provided on the label and discarding bottle 1 week (7 days) after that date. (See Storage under Stability.)
To minimize the risk of contamination of the dropper tip and solution, take care not to touch the eyelids or surrounding areas or any other surface with the dropper tip of the bottle. Importance of keeping the bottle tightly closed when not in use.
Importance of removing contact lenses prior to administration of each dose, since the benzalkonium chloride preservative may be absorbed by soft lenses. May reinsert lenses at least 15 minutes after cysteamine instillation.
Importance of advising patients that cysteamine hydrochloride ophthalmic solution is for ophthalmic use only.
Importance of continued adherence to therapy since cystine crystals accumulate if use of cysteamine ophthalmic solution is discontinued.
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as any concomitant illnesses.
Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.