Aesthetic Dermatology Update

Microtox and Mesotox

Publish date: November 16, 2022

The terms Microtox, MicroBotox, Mesotox, and MesoBotox have been thrown around in the dermatology literature, clinical medicine, and the media, leaving patients confused about what they treat and physicians confused about what patients want when they mention one of these terms.

Let’s settle the nomenclature confusion. In this column, I define and outline suggested terminology based on studies and my 15 years of experience using neuromodulators. If any readers or colleagues disagree, please write to me and we can discuss the alternatives in a subsequent article; if you agree, please also write to me so we can collaboratively correct the discrepancies in the literature accordingly.

Dr. Lily Talakoub

The term mesotherapy, originating from the Greek “mesos” referring to the early embryonic mesoderm, was identified in the 1950’s by Dr. Michel Pistor, a French physician who administered drugs intradermally. The term was defined as a minimally invasive technique by which drugs or bioactive substances are given in small quantities through dermal micropunctures. Drugs administered intradermally diffuse very slowly and therefore, stay in the tissue longer than those administered intramuscularly.

Thus, Mesotox is defined not by the concentration of the neuromodulator or location, but by the depth of injection in the superficial dermis. It can be delivered through individual injections or through a microneedling pen.

Microtox refers to the dilution of the neuromodulator at concentrations below the proposed dilution guidelines of the manufacturer: Less than 2.5 U per 0.1 mL for onabotulinumtoxinA (OBA), incobotulinumtoxinA (IBA), and prabotulinumtoxinA (PBA); and less than 10 U per 0.1 mL for abobotulinumtoxinA (ABO), This method allows for the injection of superficial cutaneous muscles softening the dynamic rhytids without complete paralysis.

Mesotox is widely used off label for facial lifting, reduction in skin laxity or crepiness, flushing of rosacea, acne, hyperhidrosis of the face, keloids, seborrhea, neck rejuvenation, contouring of the mandibular border, and scalp oiliness. Based on a review of articles using this technique, dilution methods were less than 2.5 U per 1 mL (OBA, IBA) and less than 10 U per 0.1 mL (ABO) depth of injection was the superficial to mid-dermis with injection points 0.5 cm to 1 cm apart.

In a study by Atwa and colleagues, 25 patients with mild facial skin laxity received intradermal Botox-A on one side and saline on the other. This split face study showed a highly significant difference with facial lifting on the treated side. Mesotox injection points vary based on the clinical indication and area being treated.

The treatment of dynamic muscles using standard neuromodulator dosing protocols include the treatment of the glabella, crow’s feet, forehead lines, masseter hypertrophy, bunny lines, gummy smile, perioral lines, mentalis hypertonia, platysmal bands, and marionette lines.

However, hyperdilute neuromodulators or Microtox can effectively be used alone or in combination with standard dosing for the following off-label uses. Used in combination with standard dosing of the forehead lines, I use Microtox in the lateral brow to soften the frontalis muscle without dropping the brow in patients with a low-set brow or lid laxity. I also use it for the jelly roll of the eyes and to open the aperture of the eyes. Along the nose, Microtox can also be used to treat a sagging nasal tip, decrease the width of the ala, and treat overactive facial muscles adjacent to the nose resulting in an overactive nasolabial fold.

Similarly, Microtox can be used to treat lateral smile lines and downward extensions of the crow’s feet. In all of the aforementioned treatment areas, I recommend approximately 0.5-1 U of toxin in each area divided at 1-cm intervals.Mesotox and Microtox are both highly effective strategies to treat the aging face. However, the nomenclature is not interchangeable. I propose that the term Mesotox be used only to articulate or define the superficial injection of a neuromodulator for the improvement of the skin that does not involve the injection into or paralysis of a cutaneous muscle (“tox” being used generically for all neuromodulators). I also propose that the term Microtox should be used to define the dilution of a neuromodulator beyond the manufacturer-recommended dilution protocols – used for the paralysis of a cutaneous muscle. In addition, I recommend that the terms MicroBotox and MesoBotox no longer be used. These procedures all have risks, and adverse events associated with Microtox and Mesotox are similar to those of any neuromodulator injection at FDA-recommended maximum doses, and dilution and storage protocols and proper injection techniques need to be followed. Expertise and training is crucial and treatment by a board-certified dermatologist or plastic surgeon is imperative.

Dr. Talakoub and Naissan O. Wesley, MD, are cocontributors to this column. Dr. Talakoub is in private practice in McLean, Va. Dr. Wesley practices dermatology in Beverly Hills, Calif. This month’s column is by Dr. Talakoub. Write to her at dermnews@mdedge.com. Dr. Talakoub had no relevant disclosures.