Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Heart Drug Effective for Treating Symptom of Muscular Dystrophy

A medication most often used to treat heart arrhythmias also reduces a central symptom of myotonic dystrophy, the most common type of muscular dystrophy in adults.

The findings about the medication mexiletine – a chemical cousin of lidocaine – were published May 4 in the journal Neurology, a publication of the American Academy of Neurology.

Currently there is no drug approved to treat myotonic dystrophy, an inherited disease that is marked by progressive muscle weakness. While the course of the disease can vary dramatically from patient to patient, symptoms besides weakness can include muscle stiffness, difficulty speaking and swallowing, problems walking, and in some patients, heart problems and cataracts. Physicians estimate that approximately 40,000 Americans have the condition.

The researchers at the University of Rochester Medical Center found that mexiletine is effective at treating the myotonia – muscle stiffness – that is at the center of the disease. Turning a key in a lock, writing with a pen or pencil, picking up and setting down a pitcher of water – all are formidable tasks for patients with myotonia. Sometimes the symptom first occurs when a patient shakes someone’s hand, then cannot relax his or her grip for several seconds.

While several doctors have suspected that mexiletene helps relieve myotonia, this is the first placebo-controlled, double-blind study to show that it actually does so, said neurologist Richard Moxley III, M.D., an author of the study and an international expert on muscular dystrophy.

“It’s important for physicians who treat patients to know that mexiletine is an option,” said Moxley, who is director of the University’s Neuromuscular Disease Center and professor of Neurology. “Several physicians who specialize in treating patients with myotonic dystrophy have found it to be effective for their patients, but we really wanted to study the issue closely. The medication really addresses myotonia quite well, with no additional risk.”

The findings come from one of the world’s premier groups focusing on research and new treatments for muscular dystrophy. Ten years ago Moxley began the world’s first muscular dystrophy registry, which now includes more than 1,500 patients with either myotonic dystrophy or facioscapulohumeral dystrophy.

Moxley also heads the University’s Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, one of three research centers originally created in 2003 by the National Institutes of Health. The Rochester center is now one of six NIH Wellstone centers and most recently received $5 million in additional funding in September 2008 to continue its work for five more years.

In the trial of mexiletine, evaluators measured the amount of time it took patients to relax their grip after squeezing the handles of a computerized device that measures force. For most healthy people, that relaxation takes one-third of a second or less. But for people with myotonic dystrophy, that relaxation can take many seconds.

Scientists studied two groups of 20 patients who had myotonic dystrophy, all confirmed through genetic analysis. Each participant received either placebo, or 150 or 200 milligrams of mexiletine three times a day, for seven weeks. Then, after a period of several weeks where they received no drug, participants were switched to the other treatment for another seven weeks.

The team found that mexiletine at three daily doses of either 150 or 200 milligrams per dose does a great deal to alleviate myotonia. In their test of relaxation after grip, the team found that mexiletine reduces the abnormally long relaxation by 38 percent at the lower dose and 59 percent at the higher dose. No benefit at all was seen for participants on placebo.

Because the drug can affect the heart, participants in the study were admitted as inpatients and stayed several nights at the University’s Clinical Research Center, where their heart health could be monitored closely. The team found no adverse effects of mexiletine, including no effects on normal cardiac rhythms.

Mexiletine acts to help the muscle compensate for the ion channel abnormality that is at the core of the myotonia in this disease. The myotonia is caused by a sort of molecular stutter that causes electrical signaling in muscle cells to go awry, in effect making muscle stick in the “on” position. The mutation markedly reduces the number of functioning muscle chloride channels and causes decreased movement of the chloride ion across the muscle membrane, leading to excessive muscle irritability and repeated spontaneous activation of muscle fibers. This results in muscle stiffness and delayed relaxation after contraction. Mexiletine works through the sodium channel, which is functioning normally, to decrease muscle irritability.

The new research findings on the effectiveness of mexiletine come amid several exciting research finds by Moxley’s colleagues. In one line of research, led by Charles Thornton, M.D., researchers have discovered precisely how a faulty gene actually causes myotonic dystrophy by preventing normal proteins from doing their jobs. Thornton’s group then used experimental compounds to break up abnormal cellular deposits of toxic RNA in the nuclei of cells, eliminating myotonia in mice with myotonic dystrophy. Down the hall, a team led by Rabi Tawil, M.D., is part of an international study examining the genetic roots of the second most common form of muscular dystrophy in adults, facioscapulohumeral muscular dystrophy.

In addition to Moxley, authors of the paper include Neurology faculty members Eric Logigian, M.D., and Charles Thornton, M.D., and Biostatistics faculty member Michael McDermott, Ph.D. Also taking part from Rochester were William Martens, Richard Moxley IV, Nuran Dilek, A. T. Pearson, Cheryl Barbieri, and Christine Annis. Allen W. Wiegner, Ph.D., of Harvard also contributed.

The work was funded by the Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, the U.S. Food and Drug Administration, the National Institutes of Health, the Muscular Dystrophy Association of America, and the Saunders Family Neuromuscular Research Fund.

For Media Inquiries:
Tom Rickey
(585) 275-7954
Email Tom Rickey

Tom Rickey | EurekAlert!
Further information:

More articles from Health and Medicine:

nachricht Resolving the mystery of preeclampsia
21.10.2016 | Universitätsklinikum Magdeburg

nachricht New potential cancer treatment using microwaves to target deep tumors
12.10.2016 | University of Texas at Arlington

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>