Electromedical Technology
Offers Non-Invasive Treatment Options

Iontophoretic drug delivery system, bone growth stimulator hold promise for patients

by Frances Richards

Electrically-assisted patch system delivers medicine to a young patient

Non-invasive and comfortable are two words patients never tire of hearing from their caregivers. Recent advances in electromedical technology are offering unprecedented promise of both comfort and efficacy in the quest for perfect -- or, at least, improved -- health. Two technologies -- one offering drug delivery via a supercharged "patch" system, the other presenting a non-surgical treatment for healing fractures -- are part of what doctors, scientists and patients call the future of medicine, which is striving to become as non-disruptive as possible to patients' lifestyles.

Transdermal iontophoretic delivery

A new line of electrically-assisted patch systems is now under development by Becton, Dickinson & Company (BD), Franklin Lakes, NJ. These transdermal systems deliver medications by iontophoresis, a technology BD has been actively studying since 1986. Iontophoresis is a noninvasive technique that uses a mild electric current to deliver drugs through the skin to the bloodstream.

Iontophoretic patch systems are drug-filled, miniaturized battery-powered units with integral microcomputer controls. They are worn in the same way as traditional "passive" patches, and provide all the benefits associated with transdermal delivery including avoidance of gastrointestinal and hepatic first-pass metabolism, noninvasive, continuous drug infusion and enhanced compliance.

An additional benefit is that iontophoresis is suitable for more drugs than ever before possible. With traditional passive transdermal therapy, drugs must be potent, have a low molecular weight, and be sufficiently lipophilic in order to be absorbed by the skin. However, iontophoresis is not limited by these constraints. As a result, the range of drugs that can be delivered transdermally is greatly expanded. Iontophoresis has the capability of delivering up to 50mg per day of a small (under 500 mol w) drug, such as lidocaine, a topical anesthetic. BD has also conducted trials that have successfully delivered larger drugs, such as peptides with a 3500 mol w. Multiple clinical trials have been conducted involving hundreds of subjects, a variety of drugs, and numerous operating parameters, including patch size, delivery duration and electrical current. Some of the drug applications tested include the administration of topical analgesics, hormone replacement therapy and parathyroid hormone.

How the patch works

One of the patch's gel reservoirs is prefilled with a drug. Drugs with a positive charge (D+) are placed in the positive reservoir, or negatively charged drugs in the negative reservoir. When the patch is applied to the skin, the preprogrammed microprocessor and battery initiate an ele ctric current between the electrodes. "The microprocessor can be programmed to mimic the body's natural cycle, for example during hormone delivery. This is a huge improvement over traditional drug delivery systems, such as oral or injectable, where the body receives medicine in just one or two doses per day," says John Nies, manager of controller development.

An ion exchange between the electrode and the drug forces the drug into the skin at the active electrode site. An opposite reaction at the return electrode completes the electrical circuit, where the return reservoir contains a saline solution. Total drug delivery is proportional to the total applied current.

"Drug delivery really depends on two factors in this system -- how much current is delivered and how long the current is applied," explains Nies. "The electronic controller concept is not too complex -- it contains a battery, a simple embedded processor, and a controllable current source."

On reusable systems, the microcomputer can be saved and inserted into the next prefilled patch system. In addition, buttons can be incorporated into the patch to allow self-medication by patients.

For more information:

Circle 672 -BD Pharmaceutical Systems or connect directly to their website via the Online Reader Service Program at http://www.1rs.com/007md-672

Bone growth stimulator aids healing of nonunion fractures

Each year, more than 300,000 people suffer fractures that will not heal. Sadly, 85% of these patients will not get a doctor's prescription for a bone growth stimulator that could mend these fractures -- because they don't know to ask for it.

Physio-Stim bone growth stimulator

Electrical currents have been used to heal broken bones since the mid-1800s. However, it was not until the mid-1950s that scientists made the discovery that when human bone is bent or broken, it generates its own electrical field. The connection between these naturally occurring electric fields and the healing process lead researchers to speculate that externally applied electrical fields could be used to enhance or accelerate bone healing.

The first bone growth stimulator was approved by the FDA in 1979 as a safe, nonsurgical treatment to aid in the healing of fractures. Bone growth stimulators use a very low-strength pulsed electromagnetic field (PEMF) to activate the body's natural healing process, which -- in five percent of the six million patients annually who suffer bone fractures -- is either absent or impaired.

Physio-Stim, a bone growth stimulator by Orthofix International, Richardson, TX, is a non-surgical treatment that aids in the healing of non-union fractures (fractures that will not heal on their own). A recent clinical trial indicates that none of the study's 729 patients' fractures had healed on their own by a minimum of two months post-injury (range 60 days to more than one year). However, using Physio-Stim, nearly 85 percent of these patients were able to attain fracture healing by using this device alone. Forty-eight percent of patients had previously undergone one or two -- or more -- procedures such as internal/external fixation that did not heal their fractures.

Bone growth stimulator for spine fusion

Another product from Orthofix -- Spinal-Stim -- is the first FDA-approved external bone growth stimulator for spine fusion. The battery-powered circuit sends low-level electrical signals directly to the fusion site. Spinal-Stim consists of a pair of electromagnetic coils covered in soft material and is worn around the back and over the abdomen, over clothing, for a minimum of two hours per day. The device produces an electrical signal at the fusion site similar to the one the patient's own body generates to induce normal bone healing.

A low-strength pulsed electromagnetic field activates
the body's natural healing process

Due to the low-energy output of the device, there is no direct sensation to the patient. However, the electric fields are sufficient to enhance the activity of cells at the fusion site, resulting in increased healing rates. This is significant since the lumbar region of the body is recognized as one of the slowest and most difficult areas in which to achieve bone fusion. Non-healing (i.e., failed fusion) is seen in up to one-third of all spinal fusion cases, according to published studies. In addition to spine fusion, bone growth stimulators have been FDA-approved to treat long bone fractures, too -- bones such as the tibia, fibula and femur.

Osteoporosis next

It appears that bone growth stimulating devices also may have a dramatic impact on fighting osteoporosis, which afflicts 28 million American sufferers, 80 percent of whom are women. The National Osteoporosis Institute (NOI), Commack, NY, recently received approval from the FDA to begin a clinical trial that will evaluate the safety and efficacy of bone growth stimulators in osteoporotic patients, measuring improvements in bone density.

The stimulator to be clinically tested by NOI, developed by Orthofix to treat patients with osteoporosis of the hips and/or spine, is designed as a comfortable chair pad that patients will sit on for several hours a day.

For more information:

Circle 671 - Orthofix Inc, or connect directly to their website via the Online Reader Service Program at http://www.1rs.com/007md-671