Making pills passť
Researchers seek ways to send drugs precisely where they are needed, minus the side effects
Whether it’s a headache or a sore knee, a toothache or a strep throat, people are used to taking their medicine in pill form. But to scientists, such drugs can be hard to swallow because the pill is a blunt tool: As it wends its way through the body, such medication may wreak side effects or fail to make it to its intended destination efficiently.
Now, with implantable pumps, tiny particles of drug, and novel materials that can release medication at a controlled rate, researchers are experimenting with new channels to deliver drugs directly to areas of the body where they can be most effective.
“There are a lot of very good drugs out there that are severely limited in their ability to treat disease because of side effects and compliance issues,’’ said Jeffrey Borenstein, a physicist at Draper Laboratory who is engineering new ways to deliver drugs to the delicate inner ear. “People have really recognized that if one could avoid unintended toxicities and target these drugs, and do that precisely, there could be an enormous benefit to patients.’’
Unconventional forms of drug delivery already exist.
Robert Langer, an MIT professor who has been a pioneer in the field, codeveloped the Gliadel wafer, a way of delivering chemotherapy directly to the source of brain cancer that was approved in 1996. He noted that already, devices such as drug-eluting stents placed in diseased coronary arteries deliver medication to specific body areas.
Novel methods of drug delivery can also help patients adhere to their medication regimen, Langer said, as with Risperdal Consta, a psychiatric drug made by Cambridge-based Alkermes, in which microspheres of medication are injected into the arm or buttock and release the drug over time.
Now, Bay State researchers are focused on getting drugs into an ever-expanding number of tissues and organs — the eye, the ear, and even a technique that could be used to mass-inoculate people against infectious disease without using needles.
In the eye disease glaucoma, for example, a major problem is patients’ compliance with the eyedrops regimen.
Dr. Daniel Kohane, director of the laboratory for drug delivery and biomaterials in the anesthesiology department at Children’s Hospital Boston, has been working with scientists at Massachusetts Eye and Ear Infirmary to develop technology that could replace a complicated drop regimen with a contact lens.
To explain how it works, Kohane uses food metaphors, comparing the drug-eluting contact lens to a pita pocket with drug stowed inside.
“The pita bread is the contact lens material, and inside we slide a doughnut of polymer with a drug in it,’’ Kohane said.
A drug could be continuously delivered to the eye through the contact lens, with a closely controlled dosage.
That could solve another problem with today’s treatments — even when properly administered, eyedrops are an imprecise way of delivering medication, since less than 7 percent is absorbed by the eye.
But Kohane noted that improving today’s treatments is only one of the driving forces for targeted drug delivery. Researchers are also working to create new ways to get the next generation of drugs into the body.
At Draper Laboratory and Mass. Eye and Ear, researchers are building an implantable pump to deliver drugs to the inner ear. This has the most promise for delivering drugs being developed to preserve and even regenerate sensory cells in the ear that are responsible for normal hearing.
“In the future, and probably not that far off, we may have the capacity to deliver drugs to the inner ear that could prevent degeneration of the sensory cells,’’ said Dr. Michael McKenna, a neurotologist at Mass. Eye and Ear. “It became apparent to us, we’re going to have the compounds and know-how to do it, but we won’t have a device that can be used in humans.’’
The inner ear presents a number of difficulties because the minuscule space is very sensitive to changes in volume. The researchers have developed a prototype of a pump being tested in animals that repeatedly pushes and pulls tiny amounts of fluid into the ear, eventually getting the drug to mix with the fluid of the inner ear.
The researchers have heard from other scientists interested in using the technology to deliver drugs to fluid that surrounds the spinal cord.
Such work isn’t just about treating diseases more effectively; it may also make medication a little less painful.
Researchers at Boston University have been working on packaging drugs into tiny charged nanoparticles, and then applying a small electric field to the skin that would open up pores, allowing the drug to reach cells that are an expressway to the immune system.
One day, such technology could be a way to give people shots without needles, and in a way that would be much faster-acting than current methods.
“That’s kind of the mass appeal — one painless little puff and you’re injected,’’ said Mark Horenstein, a BU professor of electrical engineering. “Think about Bones in Star Trek — you have a little gizmo and go up to the person and snap! It’s done.’’
Carolyn Y. Johnson can be reached at firstname.lastname@example.org.