The use of botulinum toxin type A (BoNT-A) for aesthetic purposes has significantly increased and become one of the most widely utilized procedures in cosmetic dermatology and aesthetic medicine to improve signs of facial skin aging since 1992, when the first article on its application for the aesthetic treatment of glabellar lines was published.¹ Data published by the American Society of Plastic Surgeons shows that BoNT-A injection procedures are the most commonly used aesthetic treatment in the USA in 2023, with over 5.6 million annual procedures.²

Botulinum toxin is produced by the anaerobic, gram-positive bacterium Clostridium botulinum, which was discovered and isolated in 1895. Seven different serotypes of botulinum toxin (A, B, C, D, E, F, and G) are known, produced by specific strains of Clostridium, which differ in potency, onset, duration of effect, and antigenicity. In aesthetics, only BoNT-A is used, as it is the most potent and has the longest-lasting action.³

BoNT-A inhibits calcium-mediated acetylcholine release at presynaptic motor nerve endings. This decreases the motor endplate potential and blocks nerve impulse transmission to the muscle, resulting in flaccid paralysis of the affected muscles. Its clinical effects appear within the first few days following injection and reach their maximum manifestation in two weeks, with a duration of effect of approximately four months.^4-6

To maintain results, treatment is recommended every three to four months, depending on the patient's response and the rate at which the muscle regains function.⁷

Currently, all BoNTs used for aesthetic purposes are type A botulinum neurotoxins (BoNT-A). There are three main BoNT-A products available: Dysport^® (AbobotulinumtoxinA, Ipsen), Botox^® (OnabotulinumtoxinA, Allergan), and Xeomin^® (IncobotulinumtoxinA, Merz Pharmaceuticals). Each of these products has a unique manufacturing process, contains different excipients, is approved by the relevant regulatory agencies, and has sufficient evidence to support its use.

Regulatory authorities emphasize that dose equivalencies between different BoNT-A formulations should not be established.

Accurate placement of botulinum toxin is crucial for achieving the desired results and preventing diffusion into unintended muscles.

Toxins with low and predictable spread are preferred for aesthetic use. Each serotype differs pharmacologically, so understanding their properties helps minimize diffusion-related side effects.

Factors affecting spread include the drug's characteristics, accurate muscle selection, dilution, injection technique, and dose injected. Studies show that incobotulinumtoxinA and onabotulinumtoxinA have similar diffusion, while abobotulinumtoxinA spreads more widely. In our personal experience, onabotulinumtoxinA provides more precise diffusion, making it a better toxin for full-face treatment, as several muscles are involved.^8-11

The prescribing information for Botox^®, approved by regulatory authorities, includes indications in aesthetic medicine for glabellar lines, forehead expression lines, and periocular dynamic wrinkles (crow’s feet). Despite this, off-label uses in facial aesthetic treatments are common, with extensive published evidence, as well as consensus guidelines and reviews, supporting these applications. A 2021 systematic review found published evidence on the effectiveness of BoNT-A in other areas, including the gingival smile, chin projection, and treatment of nasal wrinkles.¹²

A group of French experts in dermatology and aesthetic medicine developed a consensus in 2011, focusing on the use of onabotulinum toxin A to standardize its application for the treatment and prevention of aging in the upper and mid-face regions. These areas included the management of glabellar lines, forehead lines, periorbital lines, eyebrow elevation, nasal wrinkles, upper eyelid ptosis, and nasolabial folds.¹³

The second part of this French consensus, published in the Journal of Cosmetic Dermatology in 2011, addressed the use of Botox^® for treating facial aging in the lower third of the face and the neck. Applications included the nasolabial angle, nasal tip repositioning, dilated nostrils, perioral lines, marionette lines, depressor anguli oris, gingival smile, risorius and zygomatic perioral muscles, masseters, chin, and platysmal bands.¹⁴

In 2018, a group of Italian experts in plastic surgery, maxillofacial surgery, dermatology, and aesthetic medicine developed consensus guidelines to establish standardized protocols for the aesthetic use of onabotulinum toxin type A in various facial and neck areas. This consensus includes specific indications for the use of onabotulinum toxin type A in glabellar lines, dynamic periocular wrinkles, forehead lines, eyebrow elevation and shaping, orbicularis oculi hypertrophy, nasal wrinkles, nasal tip droop, gingival smile, masseter hypertrophy, perioral lines, marionette lines, hypertrophic chin, and platysmal bands.¹⁵

A Latin American study evaluated the satisfaction and safety of onabotulinum toxin type A in glabellar treatments for at least five years, analyzing 4,402 cases. The results showed that 92.3% of patients were "very satisfied" or "satisfied," with significant improvements in appearance and no increase in long-term complications.¹⁶

Full-face treatment with onabotulinum toxin is a technique used to rejuvenate facial appearance by injecting small doses into multiple facial areas. This comprehensive approach enables the simultaneous treatment of dynamic wrinkles in numerous regions, including the forehead, glabella, periocular wrinkles, and supralabial lines, resulting in a harmonious and natural effect across the facial surface.

The popularity of this method stems from its ability to deliver comprehensive and balanced facial rejuvenation, significantly reducing visible signs of aging, including expression lines and wrinkles, without requiring invasive procedures. Additionally, full-face treatment enhances facial symmetry and proportion, resulting in aesthetically pleasing outcomes.¹²

The most considerable amount of published evidence on BTX-A in aesthetic medicine, in terms of dosage, duration of effect, and adverse events, pertains to the upper third of the face. Therefore, further studies are needed to generate additional evidence.

In a phase III clinical study evaluating the safety and efficacy of BoNT-A in the treatment of upper facial lines, a total of 787 patients were included. Patients were assigned to receive either 40 U or 64 U of BoNT-A distributed among the frontal muscle, glabella, and lateral canthal lines (crow’s feet), or a placebo. The results showed that both doses of BoNT-A significantly improved the appearance of facial lines compared to the placebo. The efficacy was evident from day 7 and persisted until day 120 (64 U) and day 180 (40 U). The treatment was well-tolerated, with mild and transient adverse events, the most common being eyelid ptosis.⁶

Another study compared the effectiveness of glabellar treatment with Botox^® versus other aesthetic treatments such as dermal fillers and chemical peels. The results showed that, although all treatments improved dynamic wrinkles, Botox^® was superior in reducing fine and moderate lines on the forehead and periocular region. Additionally, Botox^® treatment demonstrated a more favorable safety profile, with fewer side effects compared to other treatments.¹⁷

The commonly treated areas and the doses used in these studies^6,18 were:

1. Forehead

• Objective. To reduce the appearance of dynamic forehead wrinkles.
• Typical dose. 10-20 units of Botox^®, distributed across 4 to 6 injection points.
• Special considerations. It is important to avoid excessively high doses on the forehead to prevent brow ptosis, a known side effect.

2. Glabella

• Objective. To treat expression lines in the glabellar area.
• Typical dose: 20-30 units, distributed across five injection points.
• Special considerations. This area is crucial for achieving a relaxed appearance and avoiding a permanently angry expression.

3. Periocular Wrinkles

• Objective. To smooth the wrinkles that form around the eyes when smiling.
• Typical dose. 6-15 units per side, injected at 3 points around the eye.
• Special considerations. In individuals with thin skin, a lower dose should be used to avoid a "frozen" appearance.

4. Barcode Wrinkles on the Upper Lip

• Objective. To reduce fine vertical rhytides above the upper lip.
• Typical dose: 4-6 units, distributed across 2-3 points.
• Special considerations. In individuals with thinner lips, care should be taken to avoid asymmetry or difficulty moving the lips.

Ethnic differences can influence wrinkle patterns and treatment response. For example, patients of Asian descent may have a different facial framework that requires adjustments in dosing and injection techniques.^19,20 This highlights the importance of conducting research in special populations, such as this study involving Mexican patients.

Given the lack of sufficient published evidence to support the full-face use of Botox^® in the Mexican population, this retrospective, observational, and cross-sectional study was conducted to evaluate patient satisfaction.

The objective of this study was to assess patient satisfaction with full-face treatment using onabotulinum toxin type A, as measured by the GAIS (Global Aesthetic Improvement Scale). Our working hypothesis was that full-face treatment with onabotulinumtoxinA is satisfactory for patients in a Mexican population.

A retrospective study was conducted on patients who attended the three high medical specialty clinics for full-face treatment with onabotulinum toxin type A (Botox^®) between February 2022 and March 2023. All patients signed an informed consent form, a medical history was taken, and potential adverse events were documented in accordance with the Declaration of Helsinki.

Data were collected from 34 subjects who visited the clinic for full-face treatment with onabotulinum toxin type A. For this study, full-face Botox^® treatment was defined as the application, in a single session, of 100 U of onabotulinum toxin type A distributed across nine facial zones: glabellar lines, frontal lines, periocular rhytides, nasal tip, gingival smile, marionette lines, chin, and masseters.

Subjects received injections in all areas or those determined by the treating physician during the preliminary assessment. The doses and the general criteria for identifying injection points were determined according to the Global Aesthetics Consensus: Botulinum Toxin Type A—Evidence-Based Review, Emerging Concepts, and Consensus Recommendations for Aesthetic Use, Including Updates on Complications, published in 2016.²¹

Two visits were conducted: the initial one, during which informed consent forms were signed, patients were assessed, clinical photographs were taken, and the treatment was administered. A follow-up visit 15 days after the treatment was carried out, during which clinical photographs were taken, adverse events were recorded, and patient satisfaction was assessed.

The 100 U of onabotulinum toxin type A was diluted in 2.5 mL of saline solution and administered using BD insulin needles (32G x 4 mm), injected at a 45-degree angle into the third muscular plane.

All patients had photographs taken before treatment and at the two-week follow-up consultation.

The outcomes reported by patients, including satisfaction with the treatment, were assessed using the GAIS questionnaire during the follow-up visit.

Patients were instructed to maintain a daily record of adverse events (related or unrelated to the treatment or product) and reactions at the injection site.

Data from 34 subjects (6 men and 28 women) were analyzed. The mean age of the population was 44.7 years, with a range from 31 to 73 years.

The areas that received the highest average number of units were the glabella (25.12 units), periocular rhytides (28.41 units), and the masseter (24 units). This aligns with the complexity or volume of the muscles involved. Expression lines in the frontal region, nasal lines, gingival smile, nasolabial fold (marionette lines), and chin required fewer units on average, while the nasal tip procedure required the fewest units (2 units). The location and average units per injection point and area are illustrated in Figure 1. The average number of units injected per zone is detailed in Table 1.

The areas treated included the glabella, forehead, periorbital wrinkles, nasal lines, nasal tip, gummy smile, chin, masseter, and marionette lines. Graphic 1 shows the percentages of patients treated in each area.

Graphic 2 shows the results of the GAIS questionnaire at the end of the treatment (day 15).

The patients who reported experiencing significant improvement or some improvement were 79.6%, while 93.3% of patients perceived at least some degree of improvement.

No serious adverse events or treatment-related complications were reported.

This retrospective study found a high level of satisfaction in terms of perceived improvement, as measured by the GAIS scale. But one limitation is the short-term assessment.

The highest number of onabotulinum toxin A units was applied to the glabella and periorbital wrinkles. No serious adverse events or complications were reported.

This study demonstrates a slightly more conservative approach to onabotulinum toxin A dosing for areas such as the forehead, nasal lines, and masseter compared to the results of D'Emilio et al.²⁰ However, there is notable agreement in the average doses and ranges used for key areas such as the glabella, periorbital rhytides, and chin. These similarities reinforce consistency in clinical practices, while differences may be attributed to the characteristics of the studied population. As it is well known, the Mexican mestizo population has distinct facial features compared to European populations, and specific aesthetic goals may differ accordingly.

When comparing the results of this study with the recommendations of the 2019 Italian consensus, significant differences are observed in certain areas. In particular, the consensus suggests higher doses for the masseter (50-80 units per side) and glabellar lines (25-35 units) compared to the average doses of 24 units and 25.12 units, respectively, used in this study. Conversely, for areas such as the forehead, periorbital rhytides, and chin, the average doses in this study align with the recommendations, reinforcing consistency in managing these areas.

This study found a satisfaction level comparable to other studies measuring satisfaction with specific facial areas. Although limited to patient satisfaction, the results contribute to the growing body of evidence on full-face treatment with onabotulinum toxin A, particularly in the Mexican population. Prospective and controlled studies in this population, with a longer time for evaluation of results and satisfaction, are needed to determine specific needs and treatment efficacy.