Oral use
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.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.Additional adverse effects of oral cysteamine include bad breath, skin odor, vomiting, nausea, stomach pain, diarrhea, and loss of appetite.The drug is in pregnancy category C; the risks of cysteamine to a fetus are not known but it harms babies in animal models at doses less than those given to people.For eye drops, the most common adverse effects are  sensitivity to light, redness, and eye pain, headache, and visual field defects. Interactions
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 doesnt inhibit any cytochrome P450 enzymes.
Macrostomia refers to a mouth that is unusually wide. The term is from the Greek prefix makro- meaning "large" and from Greek στόμα, "mouth".Macrostomia is characterized as a physical abnormality that causes clefts to form on the face of affected individuals. These clefts can form on either or both sides of the face, but they are most commonly seen on the right cheek and have a higher rate of occurrence in males. Macrostomia is very irregular and on average occurs only once in every 150,000 to 300,000 live births. Its unusual for macrostomia to occur on its own and it is included as a symptom for many diseases including craniofacial microsomia. The clefts result from improper development and fusion of the mandibular and maxillary processes. The clefts cause problems with facial muscle development. The origin of macrostomia is not yet fully understood: it could have multiple causes. Phenotypic variations
There are 4 distinct variations of macrostomia. Classifications are a complete lateral facial cleft, simple macrostomia, macrostomia with diastasis of the facial musculature, and isolated facial musculature diastasis. Each has a different physical appearance with varying levels of severity.The cleft associated with macrostomia is associated with improper or failed fusion of the mandibular and maxillary processes during embryonic development. This can lead to a variety of abnormalities involving skin, subcutaneous tissue, facial muscles, and the mucous membrane. The severity of each abnormality can vary from minor to severe. Environmental contaminants may play a role in causing macrostomia.