Thanks to his "hypospray," Dr. Leonard McCoy on "Star Trek" never had to deal with any dangerous needles.

The same could be true for your own doctor, since needle-free jet injectors have been available for more than 100 years. But cost and convenience have made needles a hard habit to break.

Stricter medical regulations and improved injector designs may make the switch to jet injection easier.

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This would be great news for the roughly 10 percent of us who are needlephobic.

It would also prevent needle-stick injuries — there are more than 600,000 per year in the United States alone — that carry the risk of HIV and hepatitis.

Looking like high-tech water-pistols, jet injectors release a coiled spring or compressed air to shoot medications at high speed through a tiny opening.

"The resulting pressure is powerful enough to drill into the skin," Bruce Weniger of the U.S. Centers for Disease Control and Prevention tells LiveScience.

Invented in the 1860s, jet injectors were instrumental in rapidly vaccinating large populations after World War II, accounting for an estimated one billion inoculations.

A gentle squirt?

In most cases, jet injectors can deliver drugs and vaccines just as effectively as needles.

In fact, jet injectors distribute their contents more broadly under the skin, thereby speeding up drug absorption, said Elemer Zsigmond, who heads a project to make the University of Illinois Hospital needle-free.

Zsigmond has tested many of the devices on himself, and claims they are "totally painless."

He has done studies and found that many patients rate the pain of a jet injection as zero on a scale of zero to 10.

But others find the pain about the same as a needle.

"It's still going to hurt a little," warns Weniger.

Some patients compare it to a rubber band being snapped against their skin. Bruising or bleeding can occur following the injection.

The potential for blood to splash back into the injector led to concerns in the 1980s over contamination between patients.

Consequently, many public health organizations, as well as the U.S. military, began to limit their use of jet injection, Weniger says.

But in the last decade, disposable cartridges with single-use nozzles have become available. There are now about 30-40 jet injector suppliers, specializing in the delivery of insulin, growth hormones, AIDS treatments, anesthesia and vaccines.

Jet setters

Even with the improved safety, jet injectors currently occupy only a small niche in the market. Many health-care professionals are familiar with needles and would rather not have to deal with a new piece of equipment, Weniger speculates.

Moreover, the price of the injector hardware can run to several hundred dollars, and disposable cartridges currently cost roughly three times as much as needle syringes.

However, needles come with hidden costs, Weniger says, since hospitals and clinics pay a lot of money for "sharps "disposal.

Furthermore, U.S. regulations from 2001 require that traditional syringes be replaced either with safety needles or a needleless alternative — such as jet injection.

Thanks to increased competition, "the price difference between safety needles and jet injectors has narrowed," Zsigmond says.

One final issue is speed.

Jet injectors were originally designed for mass inoculation campaigns. Now with the threat of sudden flu outbreaks and bioterrorist attacks, Weniger and others are pushing for the development of cartridge-based jet injectors that can dole out 600 vaccines an hour.

Could McCoy's hypospray do that?

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