Understanding Needle-free Pens

There has been a recent growing trend of needle-free filler injector pens. It is concerning that the use of such devices has gone viral on various social media platforms, including TikTok, with young women and even children injecting themselves with filler from injector pens, most commonly in the lips and the face.^1,2 Many of these filler pens are readily available for any member of the public to buy across different websites and apps online, including Amazon and eBay.

This article aims to explore the mechanism and science behind needle-free injector pens as well as their use both inside and outside clinical practice.

A background on needle-free injector pens

Needle-free injector pens are commonly used in the management of diabetic patients who are treated with insulin and have been widely used in other areas of medicine, such as with vaccine administration. The mechanism of action of a needle-free injector works by forming and opening cracks in the skin due to the high pressure and velocity of these pneumatic air pressure devices, with the high-speed stream penetrating the skin.³ Subsequently, the molecules are transported directly across the skin in the subcutaneous or intramuscular regions via a high velocity, which can disperse the drug over a larger area compared to a syringe technique.^4,5 It has been shown in the literature that the molecules are dispersed more widely in the tissue.³ This has proven to be an effective treatment for insulin administration and other types of medications and this same technology is now being used for filler treatment, and other aesthetic procedures, such as botulinum toxin treatment and mesotherapy.

Needle-free pens and fillers

So how does the use of these types of needle-free injector pens translate to the aesthetic world, specifically for filler-based treatment? The advantages of this needle-free approach, which is being advertised, is that it is beneficial for those with a needle phobia, it causes little or no pain and there is no risk of needle-stick injuries.

There are several studies that have demonstrated effective treatment with pneumatic administration of filler with needle-free pens.^6,7 For example, one study involved 34 participants that were treated at three clinical sites each on the face, neck, chest, and dorsal hands (total of 69 sites). The authors concluded that pneumatic injection of hyaluronic acid under high pressure provides a safe, well-tolerated and effective method for improving the appearance of wrinkles.⁸

The papers referenced have small sample sizes but have demonstrated that it is possible to have safe administration of filler with needle-free pens, with good patient satisfaction. It should be noted that these studies were performed by medical professionals with excellent anatomical knowledge.

Treatment safety

Many filler pens are being advertised on the internet as being risk-free, given that there are no needles on the device. Numerous websites, as well as some aesthetic training providers, also make the claim that there are no risks associated with injecting filler this way, and that no complications can result. There is a lack of data in the literature with regards to complications associated with needle-free filler injections, but does that really mean that there are no complications?

The issue of complications and vascular occlusion could result as a consequence of a thicker and more viscous filler coming out at a high pressure,⁹ which can be the case with a needle-free filler pen device. It is logical to say that the filler could penetrate into the deep dermal layer, which can therefore cause the product to penetrate the wall of a blood vessel under high pressure, and thus causing a vascular occlusion. This is particularly problematic if the pressure of the device is unknown by the injector, which is often the case with internet-bought pens as they commonly do not specify this. They often also do not disclose the true components of the product, so we cannot anticipate how it will disperse.

Specific cadaveric studies have been performed in order to examine the effects of needle-free injector pens. Seok et al. demonstrated in cadavers that there is a significant difference in penetration depth of materials with different viscosity and density when injected at the same pressure.⁹ Although these cadaveric studies do not use filler products, they use either latex or gelatin-based products at different viscosities and thicknesses, in order to simulate the mechanism.

Another important point is that the depth of penetration of the product is variable depending on the size of the particles of the product, the velocity of the jet, and the nozzle diameter of the injector pen. Studies have shown that the depth of penetration can go beyond the dermis floor when the nozzle diameter is beyond a certain measurement.^8,9 This means that it can be extremely hazardous to the areas of the face, for example around the lips and nasolabial creases, where there are superficial vessels. The specific dimensions and details of the injector pens are often not available, so it is challenging to predict what the outcome will be. Another consideration is that needle-free injector pens are releasing product at a high velocity and spreading the product over a larger area.^3,4,5 This means the practitioner has no control over the exact location the filler is inserted and the force of the injection. It is not possible to account for how the product will move within the tissues and in which anatomical plane it will spread.

As aesthetic providers, we are well aware that precise and very careful placement of product is required in the world of facial aesthetics. The primary reason for this is to minimise the risk of coming into contact with the facial anatomy danger zones. As providers, we need to have total control of where our needle tip is, as well as the need to have extensive knowledge of the anatomy and anatomical planes, and to know how much volume is being injected. An Instagram video created by US plastic surgeon Dr Michael Keyes provides an interesting comparison between dermal filler precision and needle-free filler pen precision, which all practitioners should watch before considering the use of these devices.¹⁰

Reported complications

Complications have been reported globally from the use of needle-free injector pens, and these include vascular occlusion, haematomas, infections, and an increased risk of lumps and cysts.^11-13

The two complications groups in the UK kindly shed light on this topic for this article as they have identified several reported complications as a result of needle-free filler injections. Gillian Murray, prescribing pharmacist and founding board member of the Complications in Medical Aesthetics Collaborative (CMAC) group, stated, “Volumising, cross-linked hyaluronic acid dermal fillers are not designed to be administered by needle-free devices. The pressure differential caused by the device, on expulsion of the product, may cause changes to the physicochemical and rheological properties, ultimately damaging these filler products. Excessive trauma and pain are likely to result from using this method of administration, and deposition is uneven and less accurate compared to needle delivery. It is also important to note this is an ‘off-license’ use of dermal fillers as a device. CMAC are aware of several cases of excessive trauma, bruising and haematoma, including a case of vascular occlusion and strongly advise against using these devices. Ultimately, claims of less risk and less pain cannot be substantiated or evidenced.”

The Aesthetics Complications Expert (ACE) Group World has also reported complications following injections with needle-free injector pens. On behalf of the ACE Group World, chair Dr Martyn King stated, “The ACE Group World received a call on their emergency helpline from a GP seeking advice about a female patient who had received dermal fillers from a non-medical provider using an auto-injection device. Aesthetic nurse prescriber Linda Mather, who received the call, was concerned and agreed that the bruising was more severe than you would expect from a typical filler treatment. The conclusion was that the patient had extensive bruising, which did eventually fully resolve, but caused the patient considerable distress requiring a high level of support.” Figure 2, which has been provided by the ACE Group World, shows the ecchymosis present on the patient’s face as a result of the needle-free injector pen filler treatment.

Another complication has also been reported by aesthetic nurse prescriber Frances Turner Traill, who treated a patient presenting with impending necrosis, haematoma and vascular occlusion following a needle-free filler treatment performed by a beauty therapist.¹¹

Combining needle-free injector pens with self-injection

Alongside the use of needle-free pens by practitioners comes the dangerous use by the public. I must emphasise the dangers of self-injecting, no matter whether it’s a needle or a needleless pen. Self-injecting is very challenging, even for experienced injectors. It is difficult to appreciate the angle and exact location of your injecting device. Alongside this, there is no level of precision with these devices, so it’s unclear to the injector where the product may end up. The importance of knowing your anatomy in detail, and being aware of your anatomical planes, is imperative and it is unclear to those self-injecting where the danger zones lie. The concept of the public self-injecting filler into their faces even without needles, is quite frankly terrifying.^1,2,12

More research is needed

Some studies indicate that in skilled and trained, medical hands, needle-free filler injector pens can be effective; however, it is important that if practitioners are to use these devices, they should be clear of the exact product’s characteristics, the device’s pressure, and have excellent anatomical knowledge. They should also know that the precision cannot be the same as a needle or cannula.

It is important that both practitioners and the public are aware that it is inaccurate to say that the devices are complication-free and completely safe. These statements are luring the public, and certain aesthetic providers who use these devices, into a false sense of security. Further studies looking at the potential for complications are needed.

Aesthetics Clinical Advisory Board Lead Mr Dalvi Humzah says… 

Historically, needle-free injectors were developed for mass vaccination programmes and then were used in dermatology to allow instillation of dermal treatments such as steroids intradermally for hypertrophic and keloid scars; subsequent developments in medical uses for insulin injections were also developed. It is not surprising that this technology is being introduced into the aesthetic sector. Dr Soni presents the current issues regarding the use of this technology in aesthetics with the associated adverse reports that are being reported.

One of the main concepts in aesthetic treatments is the accurate placement of products in specific layers of the body. A needle-free delivery requires a high pressure to allow products to penetrate the skin; the higher the speed and pressure of delivery, the deeper the penetration; however, this is also determined by the relative tissue characteristics of the patient. The more compact and denser the tissue, the more resistance to deeper delivery of the product. This, therefore, makes it difficult to consistently deliver products at a specific depth in every patient.

In time, this technology will be of use in specific situations and be a useful adjunct in the aesthetic sector. It does, however, raise the question of the use of new technologies in aesthetics; as a specialty this is a new field and before we start to use new technologies, they must be looked at critically and evaluated in clinical use in an evidence-based manner. This analysis and determination of use must be applied to all new devices now and in the future.