Poly-L-lactic acid is an absorbable, semi-permanent, injectable implant that can be used to gradually restore volume and stimulate collagen formation. It is FDA-approved for the correction of facial fat loss associated with antiretroviral therapy-induced lipoatrophy in HIV patients. It is FDA-approved for use in immunocompetent people to correct nasolabial fold deficiencies and other facial wrinkles. It has been used off-label to enhance the cheeks, hands, neck, and thighs.
It has also been used off-label for gluteal enhancement and chest wall deformities, such as pectus excavatum or thoracic deformities secondary to surgical procedures. Poly-L-lactic acid has been reported to improve “step off” chest wall deformities after mastectomy and implant reconstruction, suggesting that this product can also help improve breast abnormalities. For maximal correction, a series of injections is recommended at 3 to 6-week intervals. The degree of lipoatrophy correction is based on the number of sessions, not the volume injected at each session.
Mechanism of Action
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Injection of poly-L-lactic acid into the deep dermis or subcutaneous tissue may cause an immediate augmentation of the treated tissue. This is a temporary but immediate response due to tissue edema and fluid from the reconstitution of the product. It will resolve within 2 to 3 days after injection. Once the carrier substance is absorbed, the poly-L-lactic acid particles induce an inflammatory response through phagocytosis by tissue macrophages. This is a similar process to suture reabsorption in the skin. The inflammatory response breaks down the poly-L-lactic acid into lactic acid monomers. It is then metabolized to carbon dioxide and water while stimulating the production of new collagen type-I fibers in the skin. Approximately half of the product is digested within six months. The duration of action is 12 to 24 months.
Poly-L-lactic acid is microparticles of lyophilized, alpha-hydroxy acid polymers similar in structure to the polyglactin 910 suture material manufactured in powder form. Poly-L-lactic acid comes in a carton containing two vials. Each vial contains 367.5 g of product and is reconstituted with 4 mL of sterile water and 1 mL of lidocaine, producing a 5 mL suspension of 4.45% poly-L-lactic acid. Higher dilution volumes can be used. Once diluted, it should be allowed to stand undisturbed for 2 to 4 hours and swirled immediately before injection to ensure an even suspension of particles. Some injectors recommend dilution 24 to 72 hours before injection to allow appropriate saturation of the powder.
The product does not require refrigeration once reconstituted. The poly-L-lactic acid is placed into the deep dermis or subcutaneous tissue using a 26-gauge needle, roughly one vial per side of the face. Various injection techniques can be used, including linear threading, depot injection in small volumes, and cross-hatching. Massage should be performed during and after the injection to ensure an even distribution of the material. The patient should apply ice packs to the treatment areas to reduce erythema and swelling.
Acute injection site reaction is the most common adverse effect of this product. This can manifest as erythema, swelling, or bruising that can take up to one week to heal. This risk increases if the patient takes a blood-thinning agent, such as aspirin, warfarin, clopidogrel, apixaban, rivaroxaban, and dabigatran. Clinicians should carefully review the patient’s medication list and counsel them regarding the increased risk.
Poly-L-lactic acid is a foreign substance. Therefore, it carries the risk of a hypersensitivity reaction upon injection into the skin. Patients should remove all makeup, and the skin should be adequately prepped before injection to minimize the introduction of additional foreign particles. Skin testing can be performed before treatment.
Post-treatment nodules with granuloma formation can occur with an injection of this product. The risk is thought to be due to lower dilution volumes, and studies have shown that a decreased risk exists when dilution of volumes of 7 mL or more is used. Post-injection massage recommended to be performed for 5 minutes at a time, five times a day for five days after injection, has been anecdotally recommended to help minimize the occurrence of the nodules. Injectors can also place smaller aliquots of the product deeper in the skin to help minimize this risk. Several treatments can be initiated if the patient experiences nodule formation. Early-onset lesions can be treated with subcision or injected with sterile water. Later onset nodules can be treated with intralesional triamcinolone up to 40 mg/mL or 5-fluorouracil 2% or 5% combined with a low-dose oral tetracycline antibiotic. There are some reports that oral prednisone may be used to help suppress the formation of nodules.
Inappropriate placement of this product in the skin can lead to lumpiness or visibility of the filler through the skin. Post-treatment massage to the area can help decrease this risk.
Post-procedural infection is rare but can occur. The skin should be prepped with an antiseptic, such as alcohol, followed by chlorhexidine or chloroxylenol. Some injectors inquire about a history of HSV and provide adequate prophylaxis of antivirals up to 2 days before and two days after treatment if augmentation is performed on or around the lip.
The most feared complication of an injectable product is skin necrosis due to cannulation of the product into a vessel with subsequent embolization or compression of a vessel from excessive volume. Injectors should have a thorough understanding of the anatomy of the treatment area and be aware of any potential danger zones. Injection of low volumes over multiple treatment sessions should be used whenever possible. Aspiration should be performed before injecting the product into the tissue. In the event of a vascular compromise, methods to promote vasodilation should be employed. The area should be treated with a warm compress and topical nitroglycerin to promote vasodilation.
Absolute contraindication to treatment is a known allergy to poly-L-lactic acid or any of its components. Injection should not be performed if there is an active infection in the treatment area.
All patients should be assessed before treatment for facial asymmetry and volume differences. It is also important to document any preexisting scars and inquire about a history of keloid formation. All patients should receive baseline photographs and return for assessment 2 to 4 weeks after injection. Patients should be advised to avoid any unnecessary herbal medications and supplements to decrease the risk of bruising. Anticoagulants should not be discontinued.
There is no antidote to dissolve poly-L-lactic acid. In the event of a vascular compromise, methods to promote vasodilation should be employed. To promote vasodilation, the area should be treated with warm compresses and topical nitroglycerin.
Enhancing Healthcare Team Outcomes
Poly-L-lactic acid is an absorbable, semi-permanent, injectable implant that can gradually restore volume and stimulate collagen formation. It is FDA-approved for the correction of facial fat loss associated with antiretroviral therapy-induced lipoatrophy in HIV patients. While this dermal filler is usually only injected by dermatologists and plastic surgeons, primary care providers and nurse practitioners should know which patients may benefit from poly-L-lactic acid. Patients need to be educated about its side effects, potential complications, and durability. With open communication between family clinicians, specialists, and nursing staff, patients can receive optimal benefits from poly-L-lactic acid when indicated. [Level 5]
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