The effect of botulinum toxin injection dose on the appearance of surgical scar.

Early postoperative injection of botulinum toxin type A (BTxA) can reduce surgical scar hypertrophy. BTxA injection at different time points is associated with different levels of efficacy, but the efficacy of different doses of BTxA for scar management has not investigated. The purpose of this study was to investigate the effect of different doses of BTxA administered early after surgery on scar improvement through a split-scar experiment. The study included 22 patients who underwent surgery between September 2019 and October 2020. High- and low-dose BTxA was randomly administered into each half of the surgical wound closure immediately after surgery. One half of the incision was injected with a low dose (4 U) of BTxA, and the other half was injected with a high dose (8 U). The scars were then evaluated at postoperative 6 months using the modified Stony Brook Scar Evaluation Scale (mSBSES), and patient satisfaction was evaluated using the Visual Analogue Scale (VAS). The occurrence of complications or adverse events was also recorded. Twenty patients completed the study and were analyzed. Compared with the low-dose sides, the high-dose sides had significantly better mSBSES scores and significantly higher VAS scores (p < 0.01, respectively). No serious adverse reactions or post-injection complications were observed. Immediately after the operation, high-dose BTxA (that is within the therapeutic range) injection improved the appearance of postoperative scar more than low-dose injection.