A gel that can be injected directly into the source of arthritic pain and delivered metered doses of medicine as needed has been developed by researchers at the Brigham and Women's Hospital (BWH) of Harvard Medical School.

Injectables for joint paid have been around for a while but these only afford short-term relief because the injected drugs are scrubbed by the body's lymphatic system in a few hours. Implanted release mechanisms are not feasible in moving joints because of their potential as an irritant due to rubbing. Drugs encased in a gel that is then broken down by enzymes in a joint appear to hold a viable answer. These enzymes proliferate during pain episodes and thus cause the drugs to be released when they are needed.

Jeffrey Karp, leader of the research and co-director of the Center for Regenerative Therapeutics at BWH said that "the Holy Grail of drug delivery is an autonomous system that [meters] the amount of drug released in response to a biological stimulus, ensuring that the drug is released only when needed at a therapeutically relevant concentration."

In the US, some 25 million people suffer from osteoarthritis and rheumatoid arthritis. Traditional treatment is systemic involving the need to orally take a large amount of drugs to ensure that enough of it gets to a specific part of the body. This introduces other problems such as the potential for toxicity.

Researchers had to search for a gel that could provide the right packaging by being injectable with a small needle and allow drugs to be released only when needed or only when pain is present. They settled on using GRAS, a gel that literally self-packages a liquid drug into gel globules. Researchers found that gel injected into the healthy joints of mice remained stable for at least two months while holding up to the wear and tear related to that in a moving joint.

This delivery mechanism has potential use in other illnesses. "We think that this platform could be useful for multiple medical applications including the localized treatment of cancer, ocular disease, and cardiovascular disease," Karp said.