Skeletal formula (top)
Ball-and-stick model of the cysteamine
|Chemical and physical data|
|Molar mass||77.15 g·mol−1|
|Melting point||95 to 97 °C (203 to 207 °F)|
Cysteamine is a drug used to treat cystinosis; it removes cystine that builds up in cells of people with the disease. It is available in capsules and in eye drops. It is also naturally present in animals and is used by the body to make homotaurine.
The main side effects are Ehlers-Danlos syndrome, severe skin rashes, ulcers or bleeding in the stomach and intestines, central nervous symptoms, low white blood cell levels, elevated alkaline phosphatase, and idiopathic intracranial hypertension (IIH). IIH can cause headache, ringing in the ears, dizziness, nausea, blurry vision, loss of vision, and pain behind the eye or with eye movement.
The label for oral formulations of cysteamine carry warnings about symptoms similar to Ehlers-Danlos syndrome, severe skin rashes, ulcers or bleeding in the stomach and intestines, central nervous symptoms including seizures, lethargy, somnolence, depression, and encephalopathy, low white blood cell levels, elevated alkaline phosphatase, and idiopathic intracranial hypertension that can cause headache, tinnitus, dizziness, nausea, double or blurry vision, loss of vision, and pain behind the eye or pain with eye movement.
Additional adverse effects of oral cysteamine include bad breath, skin odor, vomiting, nausea, stomach pain, diarrhea, and loss of appetite.
For eye drops, the most common adverse effects are sensitivity to light, redness, and eye pain, headache, and visual field defects.
There are no drug interactions for normal capsules or eye drops, but the extended release capsules should not be taken with drugs that affect stomach acid like proton pump inhibitors or with alcohol, as they can cause the drug to be released too quickly. It doesn't inhibit any cytochrome P450 enzymes.
People with cystinosis lack functioning enzymes in lysosomes, and this leads to buildup of cystine in lysosomes, where it crystallizes and damages cells. Cysteamine enters lysosomes and converts cystine into cysteine and cysteine-cysteamine mixed disulfide, both of which can exit the lysosome.
Cysteamine is the chemical compound with the formula HSCH2CH2NH2. It is the simplest stable aminothiol and a degradation product of the amino acid cysteine. It is often used as the hydrochloride salt, HSCH2CH2NH3Cl. The comparatively high melting point of cysteamine (95-97 °C), indicates that it exists in a salt form.
In mammals is formed in the degradation of Coenzyme A when pantetheine is formed, which in turn is broken down into cysteamine and pantothenic acid. It is used in the biosynthesis of homotaurine.
Various salt forms have been worked with in labs, in clinical trials, and in marketed drugs, including cysteamine hydrochloride, phosphocysteamine, and cysteamine bitartrate; marketed capsules are the cysteamine bitartrate salt.
Society and culture
In 2013, the regular capsule of cysteamine cost about $8,000 per year; the extended release form that was introduced that year was priced at $250,000 per year.
It was studied in in vitro and animal models for radiation protection in the 1950s, and in similar models from the 1970s onwards for sickle cell anemia, effects on growth, its ability to modulate the immune system, and as a possible inhibitor of HIV.
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