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Adverse event reporting can be found at the bottom of the page
About
Adverse Reactions
Summary of the safety profile:
The most frequently reported adverse reactions are diarrhoea (9.2%), headache (9.2%), acne (6.2%), urticaria (4.6%), rash (3.8%), folliculitis (3.1%) and dizziness (2.3%)
Data from three placebo-controlled studies were integrated (130 participants on 50 mg daily and 213 participants on placebo) to evaluate the safety of ritlecitinib compared to placebo for up to 24 weeks after treatment initiation.1
This table lists all adverse reactions observed in alopecia areata placebo-controlled studies presented by system organ class and frequency, using the following categories: very common (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1,000 to < 1/100); rare (≥ 1/10,000 to < 1/1,000); very rare (< 1/10,000). Within each frequency grouping, adverse reactions are presented in order of decreasing seriousness.1
| System organ class | Common | Uncommon |
|---|---|---|
| Infections and infestations | Herpes zoster Folliculitis | |
| Nervous system disorders | Dizziness Headache | |
| Gastrointestinal disorders | Diarrhoea | |
| Skin and subcutaneous tissue disorders | Acne Urticaria Rash | |
| Investigations | Blood creatine phosphokinase increased | Platelet count decreased Lymphocyte count decreased Alanine aminotransferase increased >3 x upper limit of normal (ULN)* Aspartate aminotransferase increased >3 x ULN* |
Adapted from Litfulo (ritlecitinib) Summary of Product Characteristics1
*Includes changes detected during laboratory monitoring
Please refer to the Litfulo Summary of Product Characteristics for Further Information.
"I still can't believe what's happening to me, alopecia areata just hit me out of nowhere."
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Screening and monitoring guidance to consider when initiating treatment with Litfulo
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References:
1. LITFULO (ritlecitinib) Pfizer. Summary of Product Characteristics.
Adverse events should be reported. Reporting forms and information can be found at https://yellowcard.mhra.gov.uk or search
for MHRA Yellow Card in Google Play or Apple App Store
Adverse events should also be reported to Pfizer Medical Information on 01304 616161
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PP-UNP-GBR-13971. December 2025