Improvements in pincer nail deformity occur earlier and last longer when acetylcysteine gel is added to an overcurvature-correcting device: Results of a phase 3, multicenter, randomized, vehicle-controlled, investigator-blinded study.

Acetylcysteine (AC) destabilizes keratin and softens nails, reducing the time needed to correct pincer nail deformity with an overcurvature-correcting device. The objective of this phase 3, multicenter, randomized, investigator-blinded study was to evaluate the early and sustained therapeutic effectiveness and safety of 10% AC gel plus an overcurvature-correcting device to treat pincer nails. Patients aged 12 years and older with hallux pincer nail were fitted with an overcurvature-correcting device for 7 days, with a 24-h application of AC gel (n = 40) or vehicle (n = 39) on day 1. The primary end point (achievement of a distal narrowed nail width ratio ≥70% on day 8) was met by 47.5% in the 10% AC group and 25.6% in the vehicle group (difference 21.9%; p = 0.0439). Secondary end points showed a greater tendency towards improvement with 10% AC. The nail correction effect was maintained for at least 12 weeks in the majority of AC-treated patients, although the study duration was insufficient to assess the long-term probability of recurrence. No AC-related adverse events were reported. In conclusion, a single application of 10% AC gel combined with short-term device use facilitated earlier correction of pincer nails compared with the device alone, with improvements maintained after device removal.