Dr Ahmed El Houssieny explores the use of botulinum toxin in male facial treatments and asks, what do we know about best practice?
Botulinum toxin A (BoNT-A) is the most commonly used non-surgical aesthetic treatment in men.1 It is licensed for treatment of glabellar lines, forehead lines and lateral canthal lines (crow’s feet), but is also used off-licence in the treatment of other facial areas based on a broad consensus.2,3
Men account for around 10% of BoNT-A treatment, but its use is becoming increasingly popular with this demographic, rising 381% in the US between 2000 and 2018.1 Given this context, it is important for practitioners to be aware of key differences between men and women in their attitudes towards treatment, facial anatomy and musculature, and dosage when planning and administering a course of BoNT-A treatment.
At the initial consultation with a male patient, the practitioner should take a general medical history and any other relevant medical history, such as anticoagulant use or recent facial surgery as they would with any patient. When establishing the individual’s treatment goals, however, it is important to take into account that men may be less familiar with BoNT-A treatment than women. Despite the rise in numbers, fewer men undergo facial aesthetic treatments.
Like treating females, to support the patient in identifying their treatment goals, the practitioner should take time prior to treatment to explain fully the procedure of neurotoxin administration, including the mechanism of action of BoNT-A, risks and benefits, and what the patient might expect in their individual case. Remember to explain everything fully and clearly; in my experience, unlike academic environments for example, where men feel more at ease and ask more questions than women, in the aesthetic medicine clinic men may be less likely than women to ask questions if they do not understand.4,5
It is important to understand that men have different reasons for undertaking cosmetic treatment to women. Men often want to address signs of a ‘tired’ face and tend to opt for more subtle rejuvenation than many women.6,7 A survey carried out by the American Academy of Facial Plastic and Reconstructive Surgery found that men cite ‘competitiveness’ and ‘workplace concerns’ as motivating factors in seeking cosmetic treatment.8
In most circumstances, aesthetic practitioners should work to ensure that men retain their masculinity without appearing to have undergone a cosmetic procedure; this can be done by ensuring that the features are not softened to the extent that is seen to be too feminising.9 These preferences point towards subtle rejuvenation that ensures men do not look fatigued or are judged to be too old to have lost any competitive edge, while still being happy to retain some signs of age and experience.
Finally, while generalisations about gender are useful, the process of identifying treatment goals should always focus on the individual patient, asking what their reasons are for seeking treatment, checking their mental wellbeing, and guiding expectations. Note that it cannot be assumed that a man does not want to aim for a more flawless look or more feminised features, which will be identified in a thorough consultation.
Differences between male and female skeletal, muscular, vascular and cutaneous structures need to be accounted for when assessing the patient prior to the procedure and making a treatment plan.10
In terms of bone structure, men have a larger cranium and more prominent supraorbital ridges than women. This dictates the position of eyebrows: male eyebrows are flatter and positioned lower on the supraorbital ridge than female brows.10 Men have greater glabellar projection and a larger, wider forehead that slopes back to the hairline, which itself can recede with age, making the forehead larger.10
The lower face in men is characterised by a larger and wider chin than in women, with forward prominence11 and more prominent flexure of the mandibular ramus.12 Men have thicker skin than women and a greater density of facial blood vessels.13 The latter may be due, in part, to the presence of arteries that support facial hair in the male.14
Men also have significantly more skeletal muscle mass compared to women.10 The muscles of the glabellar complex, for example, have greater mass and strength in men but there is a great deal of individual variation.15 The greater facial muscle movement that men exercise may account for the deeper facial wrinkles that they are reported to develop.16,17
There are some exceptions to this; no difference was noted between 173 Japanese men and women in terms of upper eyelid wrinkles and in the perioral area, a cadaver study (females n=15, males n=15) found that white females typically display deeper wrinkles than white males.17,18 Over the age of 65 years, gender differences in wrinkle number and severity become less marked and women may have wrinkles of equal or greater intensity than men.17,19
Wrinkle patterns are also gender dependent; men are more likely to have a ‘V’ glabella wrinkle pattern because of a larger procerus muscle and to have a lower, rather than central or full, fan shape for lateral canthal lines.20,21
As there is much individual as well as gender variation in facial anatomy, it is important to make a careful assessment and adjust dose and injection technique accordingly. It is imperative to assess the patient’s facial muscles at rest, as well as observing movements during a range of facial expressions and by palpation, looking for areas of stronger contraction, larger dynamic movement, and deeper lines. Some practitioners find assessment tools useful in supporting this process.
Given the greater muscle mass in males, the Medicis Glabellar Muscle Mass Scale, for example, is a useful validated tool for the assessment of muscle mass in the glabellar region. It uses a range of measurements including the depth of wrinkles and brow depression at full contraction and change in the interbrow space from relaxation to contraction in order to guide dosage selection in BoNT-A treatments.15
A consensus paper on treating the forehead with BoNT-A (focusing on incobotulinum toxin A) sets out recommendations that include separate treatment protocols for men and women and describes a dynamic assessment method of the frontalis muscles based on sub divisions of muscle movement as kinetic, hypertonic and hyperkinetic.22
The efficacy and safety of neurotoxins have been shown in numerous clinical studies of glabellar, forehead and lateral canthal lines that include both female and male participants.14,15,23-26 However, studies with only male participants or with large numbers of men are few in number.27,28 Many studies include only small numbers of men and gender-specific data are not analysed to establish differences in treatment response between men and women.14
This raises the question of the extent to which the findings of many BoNT-A studies are applicable to males. One response to this question may be found in a 2019 analysis of demographics of men and minorities in clinical studies of non-surgical cosmetic procedure.29 The study examined 19 BoNT-A randomised controlled trials and found that numbers of men included in clinical trials reflects real-world demographics in terms of the proportion of men to women undergoing these procedures.29 However, further studies which focus on males or with sub-analysis of males would, in my opinion, be of great value in yielding further insights into optimising treatment with neurotoxins. While there is some published evidence for differences in male and female treatment response in the glabellar, there are no studies or subgroup analyses yet on gender differences for forehead lines or lateral canthus lines.14
Published evidence on response to BoNT-A in men in treatment of the glabellar complex consists of one study with male-only participants28 and two with subgroup analyses of gender differences.23,27 All three of these studies have shown that larger doses of both abobotulinum and onabotulinum are required in males compared with females for effective treatment of glabellar lines.23,27,28
The 2005 study of onabotulinum toxin A for treatment of glabellar rhytids (n=80) with only male participants concluded that a dose of around twice the 20U recommended dose for women was required for effective treatment in men.28 In the sub-group analysis from a 2009 phase 3 study of abobotulinum toxin A for the treatment of glabellar lines, women (n=135) were more likely to respond (investigator and subject assessments, 93% and 83%, respectively) than men (n=23; 67% and 33%, respectively) to a single 50U injection, suggesting men need an abobotulinum toxin A dose >50U.23 In the second study to offer a sub-group analysis on the efficacy of abobotulinum toxin A in males, doses of 60, 70 and 80U were found to be effective and long-lasting in men.27
It is important to note that no difference between males and females was observed in treatment-emergent adverse events in these studies,23,27 nor did the incidence of adverse effects increase with dose.27,28 No increased risk of bruising was reported in male study participants, despite the greater vascularity of the male face.27,28 This may be due to treatment of the upper face, avoiding blood vessels which are associated with terminal hairs in the lower face.14
The dose recommendations provided by such studies offer useful parameters on dose when treating the glabellar complex, however a practitioner must make their own decision based on assessment of the individual patient.
There is an absence of published data on optimal dose for males in treatment of the lateral canthi and frontalis, but we can refer to common practice which has suggested an increase of 10% to 25% above the standard dose for women.10 Some consensus papers also offer dose recommendations which take gender into consideration.22,30 It should be remembered that abobotulinum toxin A units are not interchangeable with those of onabotulinum toxin A or incobotulinum toxin A and must be converted appropriately.31
Choice of injection points, as well as awareness of interaction between muscles, is crucial to obtaining the subtle improvements that men often seek. The brows are an area of the male face that particularly require a balanced approach.
The male brow is flatter in shape than the female brow and if elevated into an arch by injection of toxin, this tends to feminise the face.10 Based on advice from the literature, when injecting the frontalis, injections should be administered in rows, including the lateral aspect of the frontalis in order to avoid lateral frontalis contraction causing arching of the brows.8,22,32
When treating the glabellar, the practitioner should be aware of the interaction between the frontalis, procerus, corrugators, and orbicularis oculi and, for this reason, should consider placing 2U ona/incobotulinum or 5U abobotulinum in the lateral frontalis above the brow, using an injection pattern of seven, as opposed to the usual five points when treating the glabellar area in order to minimise the risk of raised brows in men (Figure 1).10,20
A further male facial characteristic to be aware of in the upper face is that, when treating lateral canthal lines, more than one injection point along the inferior part of the vertical fibres of the orbicularis oculi muscle may be required. This is due to the fact that the majority of men will have a downward fan pattern of wrinkles.10,21
I recommend a follow-up visit when treating men and stress its importance, based on the fact that according to one study, men are less likely than women to return if the procedure requires some adjustment.10
Male attitudes towards non-surgical aesthetic treatment continue to develop and change but it seems likely that we will see continued growth in this patient population. While our knowledge and experience of treating the male face with BoNT-A treatment has grown, the need for further evidence to support dosing and treatment response remains.
As practitioners, we need to take gender-specific differences into account both in terms of treatment aims and anatomic differences. However, while accommodating an awareness of general principles, it is the formulation of an individualised treatment plan that will govern the choice of dose and injection site, and ensure
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