What is the duration of effectiveness for the injections?

The hyaluronic acid is a naturally occurring element in the body that contributes to tissue hydration. However, its production diminishes with age, leading to skin aging. The hyaluronic acid injections could fill in wrinkles and fine lines, increase lip volume, deeply hydrate the skin, and restore facial volume. Hyaluronic acid for aesthetic medicine injections comes in a cross-linked form. Obtained by the chemical bonding of hyaluronic acid chains, it forms a three-dimensional structure more resistant to enzymatic degradation, which extends its duration of action. Hyaluronic acid injections are minimally painful and may cause slight tingling, which can be prevented by applying a numbing cream during the session. The session lasts between 10 and 30 minutes, and the initial results appear between one and four weeks after the treatment.

Hyaluronic acid injections appear to be effective up to 24 months. Between 15 and 24 months, touch-ups may be necessary depending on the areas of the face and the amount of product injected. A study conducted on 235 patients aged 35 to 65 revealed the impact of the amount of product injected on the duration of its effectiveness. The majority of the subjects in the group who received the treatment were women. 61 patients received injections with a quantity less than 1.4 ml, 60 patients with a volume of 2 ml, 54 patients with a volume of 3.3 ml, and 56 patients with a volume of more than 3.3 ml. According to the results obtained, it is observed that the higher the volume injected, the longer the treatment's effectiveness is maintained. Indeed, a low initial volume is associated with a shorter correction. For injections of less than 1.4 ml, the median duration of the treatment's effectiveness is about 6 months while it is 18 to 24 months for quantities greater than 1.4 ml (from 2 ml to 3.3 ml). The median corresponds to the time at which 50% of patients have maintained the correction.

However, certain contraindications need to be taken into account. Indeed, this technique is not recommended for pregnant or breastfeeding women, as well as individuals on anticoagulants as the injections thin the blood, thereby increasing the risk of hematomas, prolonged bleeding, and poor healing at the injection site. Individuals with autoimmune diseases have an imbalanced immune system and could thus react to the injections. Those with a skin infection should also avoid injections as they could worsen the skin condition. It is also advised to avoid any sun exposure prior to the procedure.

The botulinum toxin is a toxin secreted by a bacterium responsible for botulism, Clostridium botulinum. This toxin blocks neuromuscular transmission by preventing the release of acetylcholine through exocytosis at the neuronal termination. It is commonly used in aesthetic medicine, particularly in the form of injections to smooth facial wrinkles such as forehead wrinkles, frown lines, and crow's feet. Injected in very small doses, botox allows for the gradual relaxation of the muscle. The effects of the botox usually appear 3 to 5 days after the initial injections, but the optimal effect is observed after 10 days. Regarding the duration of these effects, they can last 3 to 5 months depending on the treated area, the dose, and the formulation used.

Repeated treatments can also result in prolonged effects. A review encompassing three studies on the duration of botox injection effects showed an average duration of about 4.5 months, with a range from 2 to 6 months. Although a trend towards a longer duration of effect with higher doses was observed, this relationship has not been systematically studied or statistically proven. However, the most accurate estimate of the duration of botox injection effects comes from trials measuring the relapse rate, defined as the return to the initial severity of wrinkles over two consecutive visits spaced about 30 days apart. In these studies, the duration of effect varied from 3 to 5 months depending on the doses, with similar results, except for the 10-unit dose (10 U). In the groups receiving 30 and 40 U, 20% of patients were still responders at 6 months, and in the extension of a trial to 30 U, 11% of patients were still responders at 5 months. Overall, the effect lasts on average less than 4 months, but can be prolonged in some individuals.

Mesotherapy involves the localized and targeted administration of active ingredients through micro-injections into the dermis or hypodermis. This technique enhances the bioavailability of the injected substances and leverages the physiological properties of the skin to extend their effect. It involves injecting small doses of products into the skin, using a needle that is 4 to 13 mm long or an electronic injection gun. A mesotherapy session can involve several hundred injections. During the procedure, the skin undergoes numerous and intensive punctures. The micro-injuries and micro-bleeding stimulate the formation of collagen, elastin, and hyaluronic acid, as well as growth factors in the blood, which further enhances the skin's reparative effect.

The effects of mesotherapy injections in aesthetic medicine are generally temporary and vary based on several factors, including the treated area, the injected substances, and the individual characteristics of the patient. On average, the results can last from a few weeks to several months. For instance, for facial treatment, a series of 3 to 5 sessions spaced three weeks apart is often recommended, with visible effects from the first session and optimal results after about 10 days. To maintain the benefits, maintenance sessions are advised every 3 to 6 months. However, no study has demonstrated a relapse of effects over time.

Platelet-rich plasma (PRP) injections are used in aesthetic medicine to treat acne, scarring, and alopecia but are also effective for skin rejuvenation. This involves using the patient's own blood platelets to stimulate cell regeneration and improve the appearance of the skin or hair. Indeed, platelets release growth factors that promote tissue repair, stimulate collagen production, reactivate stem cells, and promote vascularization. For this, platelet-rich plasma is injected under the dermis with or without local anesthesia. When PRP is injected, it stimulates the tissue causing slight inflammation. This is when the collagen begins to develop. Approximately three months are needed to observe collagen regeneration. The results of the treatment vary but typically last up to 18 months in most patients.

However, this treatment is not recommended for individuals with metabolic and systemic disorders, and for patients taking anti-inflammatory drugs as it may reduce the effectiveness of the procedure. Some adverse effects may occur after the sessions, such as infections, skin discoloration, bruising, or allergic reactions.

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