Hyaluronidases are a types of naturally occurring enzymes used by estheticians as off-label drugs for treatment of various complications due to hyaluronic acid (HA) fillers such as necrosis, treatment of nodules, and elimination of unwanted or overcorrected HA filler volumes.
Outside of medical aesthetical industry hyaluronidases are also used as agents promoting diffusion, for example for the treatment of eye hemorrhages, for prevention of tissue damage due to extravasation of substances, and in the treatment of infertility. Hyaluronidases are sourced from sheep/bovine testes, recombinant human hyaluronidase, leeches/hookworms, or microbes.
Hyaluronidase used for aesthetic medicine are available in 10 ml ampoules of 1500 units or 15000 units. 15000 units 10 ml ampoules require reconstitution with Normal Saline to 150 units in 1 ml before injections. It is common to have cross sensitivity between allergy to bee venom (or other stinging insects venom) and hyaluronidase.
HOW IT WORKS?
Hyaluronidase acts by dissolving HA in tissues, by increasing permeability of cell membranes and tissue permeability to injectable fluids. Large doses of injected hyaluronidase can also affect intrinsic HA which is gradually restored by HA novosynthesis by fibroblasts.
DOSAGE
In general, five units of Hyaluronidase are required to destroy 0.1 ml of 20 mg/ml HA.
It should be noted that in cases of suspected vascular obstruction high doses of 450 to 1500 units should be used.
A big portion of cases of Hyaluronidase use for poorly placed filler is concerned with Lip filler and tear trough filler corrections
Compared with other areas for HA filler dissolvement with Hyaluronidase lip filler might require bigger doses due to following reasons:
-Most patients have already undergone many procedures in this area.
Lip Filler Dissolvement.
Lip filler placed incorrectly and creating “duck lip” misaligned appearance with the upper lip becoming too protruding and stiff. Normally in a case like that it is required to dissolve the old filler and start over with new filler after at least 2 weeks post dissolvement.
Doses of Hyaluronidase can range anywhere between 350 units and 1000 units in one or two sessions. Lips should be massaged thoroughly after injections of Hyaluronidase. Any new lip filler placement should take place after all the swelling and bruising from Hyaluronidase injections are gone and at least 2 weeks post filler dissolvement.
To reduce any swelling post Hyaluronidase and HA filler injections it is recommended to use oral antihistamines and to avoid strenuous exercise for one to two days, after which most of the swelling is gone.
Tear Trough Filler Dissolvement
Contrary to lip filler corrections, very low doses of Hyaluronidase are usually enough to dissolve tear trough filler. An average amount of Hyaluronidase used for tear trough correction is 10-20 units injected with 30 units BD insulin syringes using 30-31 G needles for better precision or 25G cannula for less chance of bruising in the tear trough area.
When administered, hyaluronidase starts to work immediately in the injected tissues. Its half-life is about two minutes, but it continues to work in the tissues for as long as 48 hours. Therefore, when dissolving tear trough filler, a small number of units needed to achieve a clinically significant effect, so its action continues despite degradation.
Tear trough filler when placed incorrectly is usually placed superficially, creating a build-up and a Tyndall effect (bluish tinge). In addition, due to movement of muscles around the eyes (Orbicularis oculi) with time tear trough filler sometimes is pushed to the surface creating undesired Tyndall effect. For correction of tear trough filler, routine patch test should be done first, then 15 units of Hyaluronidase should be injected in each tear trough superficially followed by a 60 second massage to help spreading Hyaluronidase in tissues. Full two weeks should be taken before re-treating tear troughs. For re-treatment of tear trough filler low density HA filler should be placed in deeper levels to prevent Tyndall effect. Very small amount of low-density filler can be placed superficially using a fanning technique with a cannula to correct darker colour in the undereye area with controlled Tyndall effect.
CONSIDERATIONS
One of the main considerations is that sometimes we do not know what filler was used or in what quantity, which makes it difficult to determine the right dosage. In cases like that, it is advisable to use Hyaluronidase in an overdose to achieve optimal results.
Patch test
It is considered a safe and recommended practice to perform a patch test before starting treatment with Hyaluronidase, except in an emergency vascular occlusion cases. Typically, between 8 and 20 units of hyaluronidase injected intradermally into the patient’s forearm followed by observation for any swelling at the site in 15-20 minutes. A positive reaction consists of a papule with arm-like protrusions that would appear in around 5 minutes and can continue for 20-30 minutes. Usually patient experiences local itching at the site as well. Passing non-lasting erythema(redness) at the test site is not usually considered a positive reaction.
Important to note that false negative patch tests can happen, so it is strongly recommended to stock the clinic with anaphylaxis kits (including benadryl and epinephrine for IM injections).
CONCLUSION
As the medical aesthetic industry develops, it is crucial for practitioners to maintain a sound knowledge of how to reverse and correct HA filler treatments. It is advisable to do patch testing before Hyaluronidase treatment. Dissolving the HA dermal filler in cases of poorly placed filler is highly recommended and in the majority of the cases is necessary before retreating with more HA filler to achieve optimal and satisfactory results.
*Information to be used as a guide only. The information is taken from the aesthetics journal.