Neuropathy: Less pain through combination therapy

01.12.2009 10:39

In addition to the pain, the patient's sleep also improved

People who suffer from severe pain due to an injury to the peripheral nervous system can be better helped by combining two common medications than with the substances administered individually. In addition to pain, the double treatment also improved patients' sleep in a comparative study.

According to estimates, around two to three percent of the population are affected by neuropathies, which, in addition to the many stories of suffering, also has enormous economic consequences. The costs for the healthcare system per patient are around three times higher than for the average population - in the USA alone this is said to be 40 billion dollars annually.

Study: Combination therapy works better

Prof. Dr. Claudia SommerThe combination of the antidepressant active ingredient nortriptyline and the antispasmodic drug gabapentin works better against so-called neuropathic pain than either substance alone, researchers from Queen's University in Kingston, Canada, now report in “The Lancet”. In doing so, they confirm clinical experiences that have also been incorporated into the guidelines of the German Society for Neurology.

“The study closes a knowledge gap in our efforts to provide patients with the best possible treatment,” says Professor Claudia Sommer, senior physician at the Neurological Clinic at the University of Würzburg. Considering the fact that combination therapy is used very frequently in practice, there has been far too little data about its effectiveness.

Neuropathies are conditions that arise from damage to the “external” (peripheral) nervous system and lead to pathological pain. Common causes of neuropathy are diabetes and infections with herpes viruses, but also vitamin B deficiency, accidents, one-sided stress or crushing of nerves, such as those that occur in bedridden older people who cannot turn over because of paralysis.

The scientists led by Ian Gilron, head of clinical pain research and anesthetist at Kingston General Hospital, began their investigation because neuropathic pain can only be incompletely controlled with the medications currently available. The problem could not be solved with higher doses of these medications, as this increased the risk of serious side effects.

In Canada, almost one in two people receive two or more medications for pain, but the benefits and side effects of such combination therapies have not been sufficiently researched. The focus was therefore on two of the most commonly used neuropathy drugs - nortriptyline and gabapentin - which were administered individually or together to 56 patients up to the highest possible tolerated dosage.

Around three quarters of the neuropathies were caused by diabetes and a quarter were due to shingles, i.e. the consequences of herpes reactivation.
On a pain scale ranging from 0 to 10, these patients had an average score of 5.4 at baseline. The data of those 47 patients who had completed at least two of the three planned treatment cycles, each lasting six weeks, were evaluated.

It was shown that treatment with gabapentin alone was able to reduce pain to an average of 3.2; Nortriptyline seemed slightly better with a value of 2.9. However, the combination treatment was clearly superior to the drugs administered individually: with both substances together, the patients' pain was reduced to an average value of 2.3 - without increasing side effects.

To the researchers' delight, the combination therapy also reduced patients' sleep disorders, which was not the case in a previous study of the combination of morphine and gabapentin compared to the individual substances.

This shows that not all combinations are equal and that such studies provide important insights, commented Professor Sommer. It is also interesting that the blood levels for both substances when the individual substances were administered do not differ significantly from the blood levels during combination therapy, even though doses of the individual medications were 10 to 20% lower. This indicates possible interactions between the drugs, which should definitely be taken into account in future studies of combination therapy.