ARTicle | InjeCTIon TeCHnIque | another10 . Therefore, a panel of experts on the aesthetic
uses of onabotulinumtoxinA convened to develop consensus recommendations for the dosage regimens5
,
which were recently revised and updated. one of the specific changes in the recommendations is the agreement that lower doses of onabotulinumtoxinA, particularly in the forehead, may help prevent a ‘frozen’ look11
. AbobotulinumtoxinA has different methods of
production and purification, and therefore has distinct chemical and biological properties. Although all the toxins ultimately interfere with the release of acetylcholine and inhibit muscular contraction, the formulations differ in their molecular weight and migration pattern, as confirmed by the overall data, and are therefore not interchangable. AbobotulinumtoxinA is quantified in Speywood units (s.u)12, 13
. The consensus recommendations
have provided detailed guidelines for safe injection, reconstitution volume, injection points, dose, and the correct injection technique for abobotulinumtoxinA. They recommend deep intramuscular injection for the glabellar lines, superficial intramuscular injection for the forehead lines and crow’s feet, and very superficial intradermal injections to create a white papula or a wheal on injection for lower eyelid wrinkles13, 14
.
Intradermal injection technique The intradermal injection technique has been used to treat transverse neck lines caused by the platysma muscle by injecting small doses over multiple sites into the deep dermis rather than subcutaneously15
. This technique
is a variation on the conventional intramuscular technique. In this technique, toxin is injected more superficially into the dermis to target the superficial muscle fibres inserting on the skin16
. The dilution used
when reconstituting a 100 unit vial of onabotulinumtoxinA (BoToX Cosmetic, Allergan, Inc.) is 5 mL non-preserved saline, thus 1 mL contains 20 units. For abobotulinumtoxinA (Dysport, Ipsen Limited) containing 500 s.u, reconstitution with 7 ml non-preserved saline produces approximately 70 s.u per 1 mL. The procedure is performed with a 1 mL syringe with a detachable 13 mm, 32-gauge needle. The injection techniques include standard sterility and skin preparation. Topical anaesthesia may be beneficial to reduce any discomfort associated with the injections in some patients. The toxin is injected intradermally to create a wheal
approximately 0.3–0.5 cm in diameter, which is less than 0.5 unit of onabotulinumtoxinA by calculation. The toxin, properly placed in the dermis, results in a wheal that will exist for a few minutes after the needle is withdrawn. The injection sites for the frontalis are in the upper half of the forehead between the arch of brows, in two to three parallel rows depending on the width of the forehead and the active transverse lines; each injection point is approximately 1 cm apart (Figure 2). Injections performed in the lower half of the forehead should be made along the animated lines with smaller, more superficial wheals to prevent brow ptosis (Figure 3). It takes approximately 5–10 units of onabotulinumtoxinA (15–30 s.u) to treat the forehead area.
26 ❚ October 2011 |
prime-journal.com Figure 2 Intradermal injection technique for the frontalis
Figure 3 Intradermal injection technique in the lower half of the frontalis performed with smaller and more superficial wheals along animated lines
Figure 4 Intradermal injection technique for the platysma
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