Diabetic peripheral neuropathy. Effectiveness of electrotherapy and amitriptyline for symptomatic relief. Diabetes Care. (1998)

From the study:

Abstract

OBJECTIVE:
To evaluate the efficacy of combining electrotherapy with amitriptyline for the management of chronic painful peripheral neuropathy in patients with type 2 diabetes.
RESEARCH DESIGN AND METHODS:
Patients (n = 26) with peripheral neuropathy were treated with amitriptyline. After 4 weeks, those patients (n = 23) who failed to respond to amitriptyline or who only had partial relief were randomized between a sham treatment group (control) or an electrotherapy group. Transcutaneous electrotherapy was given for 12 weeks by a portable unit (H-wave machine) that generated a biphasic exponentially decaying waveform (pulse width 4 ms, 25-35 V, > or = 2 Hz). The degree of pain and discomfort was graded on a scale of 0-5. An analog scale was used to record the overall change in symptoms.
RESULTS:
Amitriptyline produced some degree of symptomatic relief in 15 (60%) of the 26 patients by the 4th week; pain scores decreased from 3.8 +/- 0.1 to 2.9 +/- 0.2 (P < 0.1) and the overall reduction in pain was 26 +/- 5% on an analog scale. In the amitriptyline plus sham treatment group (n = 9), pain scores declined from 2.8 +/- 0.3 to 1.9 +/- 0.5 (P < 0.03) and the overall reduction in pain was 55 +/- 12%, suggesting a procedure-related placebo effect. In the group receiving combined electrotherapy and amitriptyline (n = 14), symptomatic improvement occurred in 12 (85%) patients. Five (36%) of the patients in this group became asymptomatic. Pain scores declined from 3.2 +/- 0.2 to 1.4 +/- 0.4 (P < 0.01) and the overall reduction in pain was 66 +/- 10%. The degree of reduction in pain scores and the incremental relief (above the amitriptyline effect) were significantly greater (P < 0.03) with electrotherapy as compared with sham treatment. The outcomes indicate a substantial beneficial effect of electrotherapy over and above any placebo influence.
CONCLUSIONS:
Our clinical observations suggest that transcutaneous electrotherapy is effective in reducing the pain associated with peripheral neuropathy. This form of therapy may be a useful adjunctive modality when it is combined with a pharmacological agent, such as amitriptyline, to augment symptomatic relief.

My Comments:

This study was conducted by the same authors of the one I reviewed in my prior blog with a focus on decreasing the pain in those with painful neuropathy. Electric stimulation parameters were identical to the prior study…
Parameters:

• Waveform:  biphasic exponentially decaying
• Duty Cycle:  continuous (I think)
• Pulse Duration:  400 uS
• Intensity:  35 mA (max)
• Rate:  user adjustable from 2-70 Hz
• Treatment Length:  30 minutes
• Training Frequency:  Daily
• Training Length:  4 weeks
• Electrodes:  4 electrodes; 2 placed on the distal quadriceps, 1 on the neck of the fibula and 1 centered on the gastrocnemius muscle (size not given).

…but what was different was the combination of electric stimulation with the drug amitriptyline. As noted in the abstract above the electric stimulation led to considerably greater pain reduction than the amitriptyline by itself. The drug seems to have helped as well, as there was an average pain reduction in the electric stim/drug group of 66% with 36% of these subjects becoming completely asymptomatic in 4 weeks. In the prior study average pain reduction of the electric stimulation (only) group was 52% with 17% becoming completely asymptomatic, so the drug and electric stimulation interaction appears to be complementary. My first question after reading this study is; what would another 4 weeks of electric stimulation do?