A Double-Blind, Split-Face, Randomized Study on the Effects and Safety of Intradermal Injection of Botulinum Toxin A (Incobotulinum Toxin A) in the Cheek

BACKGROUND: Intradermal injection of botulinum toxin A (BTXA) is used for cosmetic purposes without strong evidence for clinical use, as opposed to intramuscular injection. OBJECTIVE: To evaluate the efficacy and safety of intradermal injection of incobotulinum toxin A (iBTXA) in the cheeks. METHODS: We conducted a study with 18 volunteers who received intradermal injection of iBTXA into one cheek and normal saline into the contralateral side as a control. Volunteers visited the clinic at weeks 2, 4, 8, and 12 after injection. At each visit, pores and wrinkles were evaluated by a facial analyzer, sebum secretion by a sebumeter, skin texture by both volunteers and clinicians, and wrinkles of the nasolabial fold were graded with photographic reviews. RESULTS: There were no significant effects on the wrinkles of the infraorbital area and sebum secretion. However, there were significant improvements in the wrinkles of the nasolabial fold and skin texture on the iBTXA injected side. The effects on the wrinkles of the nasolabial fold lasted 12 weeks, and those on skin texture lasted 8 weeks. Improvement in the pore size was observed only at week 2. No serious adverse events were reported except one volunteer who complained of facial palsy after the injection of 30 units of iBTXA in one cheek. However, injection of 20 units of iBTXA in one cheek was not associated with any adverse events. CONCLUSION: Intradermal injection of iBTXA, could provide clinical benefits for skin texture and wrinkles overcoming the skin prick effect without obvious side effects.