The most commonly reported side effects of cysteine include off label use, dyspnoea, and diarrhoea, based on 4,468 FDA adverse event reports from 2004 to 2025.
Percentages show how often each reaction appears relative to total reports for cysteine.
These are voluntary reports and do not establish that cysteine caused these reactions.
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Other drugs that appear in adverse event reports alongside cysteine. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.
Also suspected
Taken alongside
Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.
43.7% of cysteine adverse event reports involve female patients and 45.1% involve male patients. The largest age group is elderly at 60%. These figures reflect who reports side effects, not underlying risk.
Sex
Age group
Conditions and purposes for which patients were taking cysteine when the adverse event was reported.
Showing 15 of 245 indications
Cysteine is sold under the brand name Elcys.
An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.
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