Background and purpose: Seroma formation is the most common complication after breast cancer surgery that cause prolonged therapy duration, increases the costs and infection rates. This study aimed at investigating the efficacy of local phenytoin application on reduction of serous fluid and drainage duration and seroma formation following modified radical mastectomy (MRM).

Materials and methods: A randomized clinical trial was performed in 31 patients who had MRM and axillary lymph node dissection (ALND). They were divided into two groups. A placebo group received normal saline (15ml) under the skin flap whereas 1% phenytoin was locally used in treatment group one day after the surgery. In further examinations, the patients were evaluated for seroma formation, surgery site infection and other complications such as hematoma or necrosis. 

Results: The mean duration of drain use in experimental group and placebo group were 3.94 and 5.92 days, respectively (P=0.01). The mean levels of serous fluid drainage were 128.3 and 210.7 ml in the group receiving phenytoin and placebo group, respectively (P=0.01). In a two-week follow-up, seroma formation were observed in both groups (treatment group: n=3 (16.7%) and placebos n=9 (69.2%)) (P=0.004). 

Conclusion: Application of local phenytoin 1% following MRM could be effective in preventing seroma formation, reducing the amount of serous drainage and shortening the drainage duration.

(Clinical Trials Registry Number: IRCT20161111786N6)