Two Drug Combo Relieves Neuropathy Pain

By Pat Anson, Editor

British researchers say a combination of two widely used drugs – an antidepressant and an opioid – can significantly relieve pain and other symptoms caused by neuropathy.

In a study published in the journal PAIN, researchers at Queens University say combining the painkiller morphine with the antidepressant nortriptyline relieved chronic neuropathic pain in nearly 90 percent of patients – significantly better than when either drug is used alone.

"Morphine and nortriptyline are excellent candidates for pain management because of the extensive research conducted on them, their low cost, and widespread availability all over the world," said Ian Gilron, MD, a professor in Queen's School of Medicine and anesthesiologist at Kingston General Hospital.

"Current neuropathic pain treatments are ineffective or intolerable for many sufferers so this new evidence supporting the morphine-nortriptyline combination is important news for patients."

Nortriptyline, an antidepressant sold under the brand names Aventyl and Pamelor, is already being used to treat pain in the arms and legs caused by multiple sclerosis. Morphine has long been used to treat both acute and chronic pain.

Neuropathic pain is characterized by tingling or burning sensations that develop as result of nerve damage caused by conditions such as shingles, diabetes, amputation, inflammation, and cancer. About 8% of adults worldwide suffer from neuropathy. Many drugs used to treat neuropathic pain, such as Neurontin and Lyrica, often don’t work or have unpleasant side effects.

In the double-blind, randomized study, 52 neuropathy patients were given a choice of trying every one of three treatments: morphine alone, nortriptyline alone, and a combination of the two drugs over six-week treatment periods. Patients were asked to record their pain levels and side effects during each treatment.

The average daily pain before treatment was 5.6, measured using a rating scale from 0-10. Average daily pain dropped to 2.6 when patients received the two drug combination. Patients taking nortriptyline and morphine alone rated their pain at 3.1 and 3.4, respectively.

Researchers said that common side effects for both drugs, which include constipation and dry mouth, did not worsen with the combined treatment.

"It's important to remember that we don't want to completely eliminate patients' ability to sense pain as it's a warning system for us, but we do want to find the right balance of pain relief and drug side effects," said Gilron

Nortriptyline and morphine are currently not available in a combined formulation. According to the Mayo Clinic, using the two drugs together is usually not recommended because they both cause sedation.

Can Viagra Treat Diabetic Neuropathy?

By Pat Anson, Editor

An experimental animal study suggest that sildenafil, an erectile dysfunction drug commonly known by the brand name Viagra, may be effective in relieving symptoms of peripheral neuropathy in men with long-term diabetes. The study is published online in PLOS ONE.

Diabetic peripheral neuropathy causes nerves to send out abnormal signals. Patients feel pain, tingling or burning sensation in their toes, feet, legs, hands or arms. Nearly 26 million people in the U.S. have diabetes and about half have some form of neuropathy, according to the American Diabetes Association. 

In previous animal studies, researchers at Henry Ford Hospital in Detroit found that sildenafil improved blood supply to the sciatic nerve and relieved symptoms of neuropathy. However, it was not known if this therapeutic effect held true for long-term peripheral neuropathy, because the diabetic mice used in the previous experiments were relatively young - 16 weeks old.

"Generally, young diabetic animals with an early stage of peripheral neuropathy are used to investigate various drug treatments," said Lei Wang, MD, the Henry Ford neuroscientist who led the research. "But patients with diabetes who are enrolled in clinical trials often are older and have advanced peripheral neuropathy.

To mimic clinical trials in which diabetes patients have advanced peripheral neuropathy, Wang and his colleagues chose male mice with type II diabetes that were 36 weeks old, roughly equivalent to middle age in humans.

In one group, 15 diabetic mice were treated with an oral dose of sildenafil/Viagra every day for eight weeks. A control group of 15 age-matched diabetic mice were treated daily with the same amount of saline.

Researchers found after a battery of nerve and function tests on both groups of mice that sildenafil markedly improved sensory function after six weeks of treatment.

“Treatment of diabetic mice at age 36 weeks with sildenafil significantly increased functional blood vessels and regional blood flow in the sciatic nerve,” said Wang. “Functional analysis showed that the sildenafil treatment considerably improved motor and sensory conduction velocities in the sciatic nerve and peripheral thermal stimulus sensitivity compared with the saline treatment.

“These findings provide new insights into mechanisms underlying the neurological dysfunction of long term diabetic peripheral neuropathy and may lead to the development of a sildenafil therapy for long term diabetic peripheral neuropathy.”

Since becoming available in 1998, Viagra has been found to relieve several other conditions beside erectile dysfunction, such as jet lag and altitude sickness. Some professional athletes also believe that Viagra enhances their performance by opening their blood vessels and increasing oxygen supply to their muscles.

Lyrica Fails in Study of Juveniles with Fibromyalgia

By Pat Anson, Editor

Lyrica, a blockbuster drug widely prescribed to treat chronic pain in adults, works no better than a placebo in treating juveniles with fibromyalgia, according to the results of a new study released by Pfizer (PFE). Lyrica is Pfizer’s top selling drug with annual worldwide sales of over $5 billion.

The double-blind Phase IV trial was conducted to fulfill a post-marketing study required by the Food and Drug Administration after Lyrica was approved for the management of fibromyalgia in adults in 2007. The generic name of Lyrica is pregabalin, which was originally developed as an anti-epileptic drug.

“The primary endpoint of the study was not achieved as there was not a statistically significant difference between pregabalin and placebo in mean pain score,” Pfizer said in a statement.

A total of 107 adolescents (ages 12-17 years) were enrolled in the 15-week study at multiple centers across the U.S., Europe and Asia. It was the first large study on the efficacy and safety of Lyrica in juveniles with fibromyalgia.

The National Institutes of Health estimates that about 5 million Americans suffer from fibromyalgia, a poorly understood disorder characterized by deep tissue pain, fatigue, headaches, mood swings and insomnia.

In the study, Lyrica was administered twice daily, starting at 75 mg/day and then increasing to up to 450 mg/day, depending on the tolerability and response of the patient. The most common side effects in the study were dizziness, nausea, headache, increased weight and fatigue. Many other patients who take Lyrica complain of similar symptoms.

"Pfizer is committed to better understanding the full clinical profile of our approved medicines in pediatric and adolescent patients. This study advances the understanding of this patient population," said Steve Romano, MD, senior vice president of Global Medicines Development for Pfizer. "These results do not change the established benefit of Lyrica for its approved indications, including fibromyalgia in adults."

In addition to fibromyalgia, Lyrica is approved by the FDA to treat chronic pain associated with epilepsy, shingles, diabetic peripheral neuropathy, and spinal cord injury. The drug is also prescribed “off label” to treat lumbar spinal stenosis, the most common type of lower back pain in older adults.

Gene Therapy Lessens Pain of Diabetic Neuropathy (VIDEO)

By Pat Anson, Editor

An experimental gene therapy reduces pain and other symptoms by over 50 percent in patients with diabetic peripheral neuropathy, according to a new study at Northwestern University.

Nearly 26 million people in the United States have diabetes and about half have some form of neuropathy, according to the American Diabetes Association.  Diabetic peripheral neuropathy (DPN) causes nerves to send out abnormal signals. Patients feel pain or loss of feeling in their toes, feet, legs, hands and arms. It may also include a persistent burning, tingling or prickling sensation. The condition can lead to injuries, chronic foot ulcers and even amputations.

Keith Wenckowski, who has type-one diabetes, says it felt “like walking on glass” when he walked barefoot in sand.   

Wenckowski and 83 other participants in the Northwestern study received two low doses of a non-viral gene therapy called VM202. They went to a clinic twice in a two-week period for a series of injections into their calf muscles and lower legs. Some received injections of a saline placebo, others a low dose of the therapy and others a higher dose.

"Those who received the therapy reported more than a 50 percent reduction in their symptoms and virtually no side effects," said Dr. Jack Kessler, lead author of the study. "Not only did it improve their pain, it also improved their ability to perceive a very, very light touch."

After three months, patients in the low-dose group experienced a significant reduction in pain compared to the placebo group. The effect persisted at six and nine months in the low-dose group.

"I can now go to a beach and walk on the sand without feeling like I am walking on glass," says Wenckowski, more than a year after receiving the therapy. "I am hoping the effects I am feeling do not cease."

VM202 contains the human hepatocyte growth factor (HGF) gene. Growth factor is a naturally occurring protein in the body that acts on nerve cell to keep them alive, healthy and functioning. Future studies will investigate if the therapy can actually regenerate damaged nerves and reverse the neuropathy.

Patients with the most extreme form of the DPN feel intense pain with a slight graze or touch. The pain can interfere with daily activities, sleep, mood and can diminish quality of life. Many drugs used to treat DPN, such as Neurontin and Lyrica, either don’t work or have unpleasant side effects.

"We are hoping that the treatment will increase the local production of hepatocyte growth factor to help regenerate nerves and grow new blood vessels and therefore reduce the pain," said Senda Ajroud-Driss, MD, an attending physician at Northwestern Memorial Hospital and an author of the study.

"We found that the patients who received the low dose had a better reduction in pain than the people who received the high dose or the placebo. Side effects were limited to injection site reaction."

The results of this Phase II, double-blind, placebo-controlled study are being published in the journal Annals of Clinical and Translation Neurology.A future, much larger Phase III study will soon be underway.

"Right now there is no medication that can reverse neuropathy," Kessler said. "Our goal is to develop a treatment. If we can show with more patients that this is a very real phenomenon, then we can show we have not only improved the symptoms of the disease, namely the pain, but we have actually improved function."