A pilot study comparing the efficacy of two formulations of botulinum toxin type A for muscular calves contouring.

[BACKGROUND] Enlarged, hypertrophy calf muscles are common in Asian women and can cause psychological burden. Botulinum toxin A (BTA) has been widely used in treating masseteric muscle hypertrophy and it's efficacious as a noninvasive method for calf-contouring has been reported. Food and Drug Administration has approved onabotulinumtoxin A (ONA, Botox; Allergan Inc, Irvine, CA, USA) for upper face rejuvenation and it has off-label uses for calf-contouring. A recently introduced Prabotulinumtoxin A (NABOTA , PRA; Daewoong Pharmaceutical, Seoul, Korea) demonstrated a comparable efficacy and safety to ONA for masseter reduction.

[OBJECTIVE] To compare the efficacy and safety of PRA and ONA gastrocnemius muscle reduction.

[METHODS] This is an experimental, randomized, controlled double-blind study. Twenty-two patients were randomized to receive 100 units PRA and ONA on each calf and were asked to come for follow-up visit for up to 6 months. Clinical photographic documentation, calf circumference measurement (upright position and tiptoe), isokinetic analysis, and ultrasonographic imaging were performed to evaluate the treatment result. In addition, patients' satisfaction and side effect were also recorded.

[RESULTS] All patients completed the study without serious side effect occurred during the whole study period. The mean calf circumference of the ONA- and PRA-treated patients in upright position at baseline was 35.42 ± 1.35 cm and 36.49 ± 2.98 cm, respectively (P = 0.137). The mean calf circumference in upright position decreased significantly as early as 2 weeks after treatment, both in ONA group and in PRA group (P = 0.004 and P = 0.003, respectively), and continued to decrease until 6 months after treatment (P = 0.002 and P < 0.001, respectively). There was no statistically significant difference in mean calf circumference when comparing between ONA and PRA group at any time of follow-up period. For the tiptoe position, only in the PRA group that showed significant reduction as early as two weeks and lasted up to 6 months of follow-up (P < 0.001). The isokinetic analysis showed no significant reduction on both maximum torque and average work value in two groups. The ultrasonographic imaging revealed that the mean thickness of the lateral head of the gastrocnemius showed significant only in PRA-treated group at 2-, 3-, and 6-months of follow-up; meanwhile, the mean thickness of the medial head showed significant reduction at 2- and 6-months, with a slight increase at 3-months follow-up in two groups. The patients' satisfaction rate and doctor's evaluation also showed no statistically significant difference between both groups.

[CONCLUSION] This study demonstrated that PRA and ONA provided comparable efficacy and safety in gastrocnemius muscle reduction.