What the label lists and what reports show
Nitisinone side effects
Nitisinone's FDA label: “Most common adverse reactions (>1%) are elevated tyrosine levels, thrombocytopenia, leukopenia, conjunctivitis, corneal opacity, keratitis, photophobia, eye pain, blepharitis, cataracts, granulocytopenia, epistaxis, pruritus, exfoliative dermatitis, dry skin …” FAERS holds 948 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is amino acid level increased (133 reports).
- Generic listed
Check it at the source: the nitisinone FDA label on DailyMed (effective November 30, 2021, SWEDISH ORPHAN BIOVITRUM AB (PUBL)); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsMost common adverse reactions (>1%) are elevated tyrosine levels, thrombocytopenia, leukopenia, conjunctivitis, corneal opacity, keratitis, photophobia, eye pain, blepharitis, cataracts, granulocytopenia, epistaxis, pruritus, exfoliative dermatitis, dry skin, maculopapular rash and alopecia.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
This table is printed in the NITYR label published by Cycle Pharmaceuticals Ltd. of December 22, 2025; the label quoted above does not print one.
| Reaction | *reported in at least 1% of patients; ** another oral formulation of nitisinone TABLE 1 Most Common Adverse Reactions * in Patients with HT-1 Treated with Nitisinone ** |
|---|---|
| Elevated tyrosine levels | >10% |
| Leukopenia | 3% |
| Thrombocytopenia | 3% |
| Conjunctivitis | 2% |
| Corneal Opacity | 2% |
| Keratitis | 2% |
| Photophobia | 2% |
| Eye Pain | 1% |
| Blepharitis | 1% |
| Cataracts | 1% |
| Granulocytopenia | 1% |
| Epistaxis | 1% |
| Pruritus | 1% |
| Exfoliative Dermatitis | 1% |
| Dry Skin | 1% |
| Maculopapular Rash | 1% |
| Alopecia | 1% |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedMost common adverse reactions (>1%) are elevated tyrosine levels, thrombocytopenia, leukopenia, conjunctivitis, corneal opacity, keratitis, photophobia, eye pain, blepharitis, cataracts, granulocytopenia, epistaxis, pruritus, exfoliative dermatitis, dry skin, maculopapular rash and alopecia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Swedish Orphan Biovitrum at 1-866-773-5274 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. ORFADIN was studied in one open-label, uncontrolled study of 207 patients with HT-1, ages 0 to 22 years at enrollment (median age 9 months), who were diagnosed with HT-1 by the presence of succinylacetone in the urine or plasma. The starting dose of ORFADIN was 0.3 to 0.5 mg/kg twice daily, and the dose was increased in some patients to 1 mg/kg twice daily based on weight, biochemical, and enzyme markers. The recommended starting dosage of ORFADIN is 0.5 mg/kg twice daily [see Dosage and Administration ( 2.1 )]. Median duration of treatment was 22 months (range 0.1 to 80 months). …
Source: FDA drug label, SWEDISH ORPHAN BIOVITRUM AB (PUBL), effective November 30, 2021 (SPL set 5d449b73-d503-4132-b978-d890491975df), via openFDA; the full label on DailyMed
What do FAERS reports show?
948 reports list nitisinone among the medicines taken, each a report of something that happened, not proof the medicine caused it; 153 are coded as a death and 294 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 3 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Nitisinone: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions