What is an Injection Without a Needle Called? Understanding Jet Injectors
An injection administered without a hypodermic needle is most commonly known as a jet injection, and the device used is a jet injector [1.2.2]. This form of needle-free injection technology (NFIT) has been used for decades in various medical applications [1.2.1]. It is a key tool for overcoming needle phobia (trypanophobia) and reducing the risk of needlestick injuries among healthcare workers [1.2.2, 1.8.1]. Unlike traditional syringes that puncture the skin, jet injectors use a different principle to deliver medication.
The Science Behind Needle-Free Injections: How Do They Work?
Jet injectors operate by forcing a pre-measured dose of liquid medication through a very small, precise opening (nozzle) at an extremely high velocity—often exceeding 100 meters per second [1.2.1, 1.3.5]. This creates a micro-thin, high-pressure stream of fluid that is strong enough to penetrate the skin's outer layer (epidermis) and deliver the drug into the underlying subcutaneous or intramuscular tissue [1.2.2]. The process generates a hole in the skin through a combination of erosion and fracture, allowing the jet to deposit the medication [1.2.2]. The entire event is incredibly rapid, often lasting for just a fraction of a second [1.2.2].
The power to generate this immense pressure comes from several types of mechanisms [1.4.3]:
- Spring-Powered: These devices use the stored energy of a compressed mechanical spring to drive a piston, which then ejects the liquid [1.2.2]. They are often compact and relatively low-cost but must be manually reset for each dose [1.2.2].
- Gas-Powered: Using a cartridge of compressed gas (like carbon dioxide or nitrogen), these injectors can generate sustained force, making them suitable for delivering larger volumes or for repeated injections [1.3.2, 1.4.1].
- Emerging Technologies: Newer systems are being developed that use Lorentz force, piezoelectric actuators, or even lasers to create the jet stream with even greater control over dose and depth [1.2.3, 1.3.2].
A Brief History of Needleless Technology
The concept of jet injection dates back further than many realize. Accidental high-pressure fluid injections were noted in industrial settings in the 19th century [1.7.2]. The idea for medical use was sparked in the 1930s, leading to the development of early prototypes [1.7.2]. The technology gained significant traction in the 1950s and 1960s with the invention of multi-use nozzle jet injectors (MUNJIs) like the Ped-O-Jet [1.7.1, 1.7.4]. These devices were instrumental in mass vaccination campaigns worldwide, including the global effort to eradicate smallpox, as they could administer up to 1,000 shots per hour [1.7.1].
However, the use of MUNJIs declined dramatically after outbreaks of Hepatitis B were linked to their use in the 1980s [1.7.2]. Investigations revealed that 'splash-back' and 'suck-back' of microscopic amounts of blood and tissue fluid could contaminate the device's nozzle, leading to cross-contamination between patients [1.2.4]. This discovery led to a shift towards safer designs. In the late 1990s, disposable-cartridge jet injectors (DCJIs) were introduced, which use a new, sterile, single-use cartridge for each patient, effectively eliminating the risk of cross-contamination when used correctly [1.2.1, 1.7.1]. These modern devices are the primary type of jet injectors in use today [1.2.1].
Comparison Table: Jet Injectors vs. Traditional Needles
| Feature | Jet Injector | Traditional Needle |
|---|---|---|
| Mechanism | High-pressure liquid stream penetrates skin [1.3.3] | Sharp metal needle pierces skin |
| Needle Phobia | Reduces or eliminates anxiety [1.5.5] | A primary cause of medical anxiety [1.8.2] |
| Needlestick Injury Risk | Eliminates risk for healthcare provider [1.2.2] | A known occupational hazard |
| Drug Absorption | Often faster due to wider tissue dispersion [1.5.4] | Slower, localized deposit of medication |
| Pain Perception | Varies; often described as a 'snap' or 'flick'. Can cause less pain than a needle, but may also cause bruising [1.9.1, 1.5.4] | Sharp, piercing pain |
| Cross-Contamination Risk | Very low with modern single-use disposable cartridges [1.2.2] | Low with proper single-use sterile technique |
| Initial Cost | High; device can cost several hundred dollars [1.5.2] | Very low (cost of syringe and needle) |
| Dose Accuracy | Modern devices are highly accurate, but improper use can lead to incorrect dosage [1.5.2] | Generally high accuracy |
Advantages and Clinical Applications
The most significant benefits of needle-free injectors are improved safety and patient comfort. They entirely prevent needlestick injuries and can significantly reduce the anxiety associated with trypanophobia [1.5.5]. This has made them valuable in various medical fields.
Common applications include:
- Vaccinations: Historically used in mass campaigns for polio and smallpox, modern devices are approved for specific vaccines, such as influenza [1.2.4, 1.7.1].
- Insulin Delivery: Jet injectors offer an alternative for diabetic patients, with some studies showing faster insulin absorption compared to needles [1.2.1, 1.5.2].
- Anesthetics: Used in dentistry and dermatology to deliver local anesthetics like lidocaine with less pain perception during administration [1.2.1, 1.6.3].
- Hormone Therapy: Growth hormones are often administered via jet injector, which is particularly appealing for pediatric patients [1.2.1].
- Dermatology and Cosmetics: Used to deliver treatments for scars, wrinkles, and hyperhidrosis (excessive sweating) [1.6.3].
Limitations and the Future
Despite the advantages, jet injectors have limitations. The initial cost of the devices is significantly higher than traditional needles and syringes [1.5.2]. While the sensation is different, they are not completely painless and can cause localized reactions like bruising, redness, or bleeding [1.5.4]. Furthermore, they require proper training to ensure correct dosage and to avoid technical issues [1.5.2].
The U.S. Food and Drug Administration (FDA) has also issued warnings against the use of any needle-free devices for injecting dermal fillers, as these uses are not approved and have been associated with serious adverse events [1.10.1, 1.10.4].
The future of needle-free technology continues to evolve. Advances in engineering are leading to more sophisticated devices with better control over injection depth and pressure [1.2.3]. Beyond jet injectors, other needle-free technologies like microneedle patches—which use tiny, dissolvable spikes to deliver a drug—are also being developed for even less invasive administration [1.6.5].
Conclusion
So, what is an injection without a needle called? It's called a jet injection. Powered by decades of innovation, from the early days of mass vaccination to modern disposable-cartridge systems, jet injectors provide a crucial alternative to needles. They offer a solution to the prevalent problems of needlestick injuries and patient phobias, with wide-ranging applications in medicine. While they have limitations in cost and use, ongoing advancements continue to refine their performance, promising an even greater role in the future of medication delivery.
For more information on the standards governing these devices, you can refer to resources from the International Organization for Standardization, such as ISO 21649:2023 [1.10.3].
