Effect of a-lipoic acid on symptoms
Clinical Report
Effect of a-lipoic acid on
symptoms and quality of
life in patients with painful
diabetic neuropathy
Evangelos Agathos, Anastasios Tentolouris ,
Ioanna Eleftheriadou, Panagiota Katsaouni,
Ioannis Nemtzas, Alexandra Petrou,
Christina Papanikolaou and
Nikolaos Tentolouris
Abstract
Objective: To examine the effect of a-lipoic acid on neuropathic symptoms in patients with
diabetic neuropathy (DN).
Methods: Patients with painful DN were treated with 600 mg/day a-lipoic acid, orally,
for 40 days. Neuropathy Symptom Score (NSS), Subjective Peripheral Neuropathy Screen
Questionnaire (SPNSQ) and douleur neuropathique (DN)4 questionnaire scores were
assessed at baseline and day 40. Quality-of-life treatment effects were assessed by Brief
Pain Inventory (BPI), Neuropathic Pain Symptom Inventory (NPSI) and Sheehan Disability Scale
(SDS). Changes in body weight, arterial blood pressure, fasting serum glucose and lipids were also
assessed.
Results: Out of 72 patients included, significant reductions in neuropathic symptoms were
shown by reduced NSS, SPNSQ and DN4 scores at day 40 versus baseline. BPI, NPSI, and
SDS in terms of work disability, social life disability, and family life disability scores were also
significantly reduced. Moreover, 50% of patients rated their health condition as ‘very much better’
or ‘much better’ following a-lipoic acid administration. Fasting triglyceride levels were reduced,
Diabetes Centre, First Department of Propaedeutic
Internal Medicine, Medical School, National and
Kapodistrian University of Athens, Laiko General
Hospital, Athens, Greece
Part of this work was orally presented at the 5th Hellenic
Congress of the Hellenic Association for the Study of the
Diabetic Foot (EMEDIP) on February 5–7, 2016, Athens,
Greece.
Corresponding author:
Nikolaos Tentolouris, Diabetes Centre, First Department
of Propaedeutic Internal Medicine, Medical School,
National and Kapodistrian University of Athens, Laiko
General Hospital, 17 Agiou Thoma Street, 11527, Athens,
Greece.
Email: ntentol@med.uoa.gr
Journal of International Medical Research
2018, Vol. 46(5) 1779–1790
! The Author(s) 2018
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DOI: 10.1177/0300060518756540
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but no difference was found in body weight, blood pressure, fasting glucose, or other lipids at day
40 versus baseline.
Conclusions: A-lipoic acid administration was associated with reduced neuropathic symptoms
and triglycerides, and improved quality of life.
Keywords
A-lipoic acid, Diabetes mellitus, Diabetic neuropathy, Neuropathic symptoms, Painful diabetic
neuropathy, Quality of life
Date received: 26 November 2017; accepted: 9 January 2018
Introduction
Diabetes mellitus is a major public health
problem, reaching epidemic proportions
globally. Approximately 9% of adults are
estimated to be affected by diabetes world-
wide, however, around half of the cases
remain undiagnosed.1 Peripheral neuropa-
thy is a common complication in patients
with diabetes, with population and clinic-
based studies suggesting prevalence rates of
5.3–47.6% for peripheral sensorimotor neu-
ropathy.2–6 Diabetic peripheral neuropathy
is associated with older age, long duration
of diabetes mellitus, poor glycemic control,
increased lipid levels and high blood pres-
sure.2 In addition to sensory loss and
motor deficits, diabetic neuropathy may be
associated with intractable neuropathic pain.
Significant improvements have been made in
therapeutic options that target mainly neu-
ropathic symptoms, but not in those that
target pathogenetic mechanisms.2 Despite
therapeutic advances, diabetic neuropathy
is still associated with substantial morbidity,
increased mortality, and impaired quality of
life (QoL) compared with patients who have
diabetes but no neuropathy.
Oxidative stress is thought to possess a
significant role in the pathogenesis of diabet-
ic neuropathy.7 A-lipoic acid, a very potent
antioxidative agent, has been shown to
improve nerve blood flow, reduce oxidative
stress and improve distal nerve conduction
in a rat model of diabetic neuropathy.8
Clinical studies investigating the effect of
a-lipoic acid on diabetic neuropathy have
revealed promising results in terms of neuro-
pathic symptoms.9–12 In addition, a recent
meta-analysis revealed that treatment with
300–600 mg/day a-lipoic acid, intravenously
(i.v.) for 2–4 weeks, was safe and significant-
ly improved nerve conduction velocity and
neuropathic symptoms.13
The aim of the current study was to
prospectively investigate the effect of
600 mg/day a-lipoic acid (Nevralip RetardVR
,
Medical Pharmaquality, Athens, Greece)
administered orally for 40 days, on symp-
toms, laboratory parameters, QoL, and over-
all health status of patients with painful
diabetic neuropathy.
Patients and methods
Study population and setting
This prospective, interventional study was
conducted at Laiko General Hospital,
Athens, Greece, between September 2015
and May 2016. Patients with type 1 or
type 2 diabetes mellitus, who were followed
at the outpatient Diabetes Clinic of Laiko
General Hospital and were eligible to
1780 Journal of International Medical Research 46(5)
participate, were consecutively enrolled into
the study. Inclusion criteria comprised the
following: (1) patient’s agreement to partic-
ipate; (2) aged 18–75 years; (3) diabetic
peripheral neuropathy diagnosis and
one typical painful neuropathic symptom
such as burning, shooting pain, paraesthe-
sia, muscle cramps or allodynia, in the feet,
for 6 months, that interfered with daily
life or sleep; and (4) if treated with medica-
tions for painful diabetic neuropathy, treat-
ment had to be stable for 3 months before
recruitment into the study. Exclusion crite-
ria comprised: (1) causes of neuropathy
other than diabetes (such as chronic alcohol
misuse, vitamin B12 deficiency, drug-
induced neuropathy), truncal neuropathy
or severe neurological diseases (such as
Parkinson’s disease and multiple sclerosis);
(2) severe renal disease defined as estimated
glomerular filtration rate (eGFR) < 30 ml/
min/1.73m2 using the Modification of Diet
in Renal Disease formula,14 or severe liver
disease; (3) recent treatment for cancer or
haematological malignancies; (4) presence
of foot ulcers; (5) peripheral arterial disease
defined as non-palpable pulses at the feet
arteries and/or intermittent claudication;
(6) use of agents in the previous 3 months
that could interfere with the interpretation
of results, such as opiates, vitamin B com-
pounds or antioxidants; and (7) pregnancy,
lactation, or childbearing age without use
of safe contraception.
Participants were prescribed 600 mg/day
a-lipoic acid (Nevralip RetardVR
), orally, for
40 days, and were advised not to discontin-
ue any medications for managing painful
diabetic neuropathy, antidiabetic drugs, or
medications used for managing arterial
hypertension or dyslipidaemia during the
study.
The study was approved by the Ethics
Committee of Laiko General Hospital,
and was conducted in accordance with the
Declaration of Helsinki (1964). Written
informed consent was obtained from all
participants.
Definition of neuropathy
Diabetic peripheral neuropathy was defined
as the presence of signs and/or symptoms of
peripheral nerve dysfunction in patients
with diabetes after the exclusion of other
causes.2 In the current study, assessment
of diabetic peripheral neuropathy included
examination of symptoms and signs, and
quantitative sensory testing. Symptoms of
somatic neuropathy were assessed using
the Neuropathy Symptom Score (NSS), as
described previously,2 and the Neuropathy
Disability Score (NDS) was used, as
described previously,15 to quantify signs of
diabetic peripheral neuropathy. The criteria
for diagnosing diabetic peripheral neuropa-
thy were NDS 6 irrespective of the NSS
values, or NDS 1⁄4 3–5 with NSS 5.2
Data collection and patient follow-up
Two visits were scheduled for data collec-
tion, physical examination and laboratory
testing of participating patients: the first
prior to initiation of a-lipoic acid adminis-
tration (baseline visit) and the second at day
40 following initiation of a-lipoic acid
(2nd visit). The following data were collect-
ed from participants’ medical records and
through personal interviews by one trained
healthcare professional (E.A.): age, gender,
type of diabetes mellitus, history of other
underling diseases, diabetes medications,
other medications, and alcohol consump-
tion. Height and weight were measured in
light clothing and body mass index (BMI)
was calculated. Systolic and diastolic blood
pressure was measured twice, 2 min apart,
with the patient in a sitting position and
the mean of the two measurements was
recorded. All measurements were performed
at the baseline visit (by E.A.) and at the end
of the study (2nd visit at day 40 [by C.P.]).
Agathos et al. 1781
Assessment of neuropathic symptoms and
QoL measures
Data regarding patients’ neuropathy symp-
toms, QoL, and patients’ perception of
overall health status were collected by one
trained healthcare professional (E.A)
during the baseline (E.A.) and 2nd visit
(C.P.) using specific questionnaires. All
questionnaires were administered via face
to face interview with the healthcare profes-
sional and without any time limit.
Neuropathy symptom scores were calcu-
lated for both visits using the following
questionnaires.
1. Neuropathy Symptoms Score (NSS),16
comprising five questions about neuropa-
thy symptoms, with a score ranging from
‘0’ (no neuropathic symptoms) to ‘10’ (the
most severe neuropathic symptoms).
2. Subjective Peripheral Neuropathy Screen
Questionnaire (SPNSQ),17 comprising 15
‘yes/no’ questions regarding symptoms
of neuropathy, with the score calculated
by summing the ‘yes’ answers, and rang-
ing from ‘0’ (no neuropathic symptoms)
to ‘15’ (the most severe neuropathic
symptoms).
3. Douleur neuropathique (DN)4
Questionnaire,18 comprising 10 ‘yes/no’
items regarding neuropathic pain, with
the score calculated by summing the
‘yes’ answers, and ranging from ‘0’ (no
neuropathic pain) to ‘10’ (the most
severe neuropathic pain).
Quality of life was assessed using the fol-
lowing questionnaires.
1. Brief Pain Inventory (BPI)-modified
short form (SF),19 comprising 11 items
(the first four concerned the severity of
patients’ pain, and the remaining seven
concerned the degree to which pain inter-
feres with the common dimensions of
feeling and function). The answers to
all items ranged from ‘0’ (‘no pain’ in the
case of the first four and ‘no interference’
in the case of the other seven) to ‘10’ (‘pain
as bad as you can imagine’ in the case of
the first four and ‘interferes completely’ in
the case of the other seven). Two scores
were calculated: the BPI severity score
(mean number of correct answers to the
first four items) and the BPI interference
score (mean number of the correct answers
to the last seven items).
2. Neuropathic Pain Symptom Inventory
(NPSI),20 comprising six scores: Total
Intensity Score, ranging from ‘0’ (none)
to ‘100’ (worst imaginable); and five
scores corresponding to dimensions of
pain, namely, burning (superficial) spon-
taneous pain, pressing (deep) spontane-
ous pain, paroxysmal pain, evoked pain,
and paraesthesia/dysesthesia (all ranging
from ‘0’ [none] to ‘10’ [worst imaginable]).
3. Sheehan Disability Scale (SDS),21 which
included three self-rated items that mea-
sured functional impairment, and generat-
ed three scores: work-disability score, social
life-disability score, and family-life disabili-
ty score, ranging from ‘0’ (no disability) to
‘10’ (worst imaginable disability).
Patient Global Impression-Improvement
(PGI-I) was also estimated during the 2nd
visit. In particular, the patient described
his/her condition, compared with how it
was before the initiation of treatment with
a-lipoic acid, using the following descrip-
tors: ‘very much better’, ‘much better’,
‘a little better’, ‘no change’, ‘a little worse’,
‘much worse’, or ‘very much worse’. The
physician who administered the question-
naires at the 2nd visit (C.P.) was not
aware of the baseline visit responses.
Laboratory assays
Blood samples (approximately 15 ml per
sample) were collected following a 12-h
overnight fast, via venepuncture of the
1782 Journal of International Medical Research 46(5)
forearm vein. Blood samples were left for
10 min at room temperature to allow clot-
ting and then centrifuged at 4042 g for 15
min at 4C. Measurements were performed
immediately following centrifugation.
Fasting serum glucose, creatinine and lipids
were measured using an automated
Technicon RA-XT clinical chemistry analy-
ser and reagents (Technicon Instruments,
Tarrytown, NY, USA) according to the
manufacturer’s instructions. The
Friedewald formula22 was used to calculate
low-density lipoprotein cholesterol (LDL-
C). Glycosylated haemoglobin (HbA1c) was
measured using high-performance liquid
chromatography, and eGFR was calculated
using the Modification of Diet in Renal
Disease formula. All measurements were
performed at the baseline and 2nd visit,
except for serum creatinine which was mea-
sured only at baseline.
Statistical analyses
Data were analysed using SPSS software,
version 22.0 (IBM, Armonk, NY, USA)
for Windows. Continuous variables are pre-
sented as mean SD, or median, minimum
and maximum values. Nominal variables
are presented as n (%) prevalence or fre-
quencies. A 95% confidence interval (CI)
was calculated to assess the difference in
mean NSS between the baseline and 2nd
Visit. Student’s t-test was used to compare
total scores/measurements between the
baseline and 2nd visit. McNemar’s test
was used to compare the percentage of
‘yes’ responses for the DN4 questionnaire
and SPNSQ between the baseline and 2nd
visit. Multivariate linear regression was
used to investigated any statistical associa-
tions between changes in NSS, DN4 ques-
tionnaire and SPNSQ scores from the
baseline and 2nd visit (dependent variables)
and the following parameters (independent
variables): age, sex, BMI, comorbidities,
arterial blood pressure and heart rate. All
tests were two sided with a 1⁄4 0.05. A P val-
ue < 0.05 was considered statistically
significant.
Sample size
The sample size was determined by the
number of patients with diabetes that could
be recruited within one year. The sample size
of 72 patients gave a very high precision
regarding the CI estimation of the difference
in NSS between the baseline and 2nd visit.
Specifically, the precision was 0.5 units and
the corresponding CI for the NSS difference
(improvement) was 2.6 0.5 (95% CI 2.1,
3.1).
Results
During the study period 96 patients with
neuropathy were invited to participate; 10
patients failed to meet the study inclusion
criteria and 14 patients were not eligible due
to exclusion criteria. Of these, 72 patients
were eligible and all completed the study
successfully. Baseline characteristics and
medications are shown in Tables 1 and 2,
respectively.
Statistically significant reductions in neu-
ropathic symptoms were noted by patients
following the 40-day administration of
a-lipoic acid, indicated by changes in NSS,
SPNSQ and DN4 scores. Mean NSS score
was 7.9 (range, 4–10) at the baseline visit
compared with 5.3 (range, 2–10) at day 40
of treatment (P < 0.001). Results of the
SPNSQ by visit revealed a statistically sig-
nificant decrease in 14 out of the 15 ques-
tions for neuropathy symptoms at day 40
compared with baseline (Table 3), while
mean SPNSQ score decreased from
8.8 (range, 3–15) at baseline to 4.4 (range,
0–14) at the end of a-lipoic acid administra-
tion at day 40 (P < 0.001). Statistically
significant reductions were also noted for
the DN4 questionnaire scores, in all 10
questions regarding pain characteristics
Agathos et al. 1783
(Table 4). In addition, patients’ mean DN4
questionnaire score was also significantly
reduced from baseline (mean score, 5.7
[range, 1–9]) compared with day 40 (mean
score, 2.8 [range, 0–8]; P < 0.001).
Regarding patients’ QoL, BPI scores
revealed a significant reduction in pain
severity (mean score, 4.3 [range, 0–9] at
baseline versus 2.3 [range, 0–9] at day 40;
P < 0.001) and pain interference (mean
score, 5.2 [range, 0–10] at baseline versus
3.2 [range, 0–9.7] at day 40; P < 0.001).
Similarly, a significant reduction in NPSI
score was noted in terms of NPSI Total
Intensity Score (mean score, 40.1 [range,
8–88] at baseline versus 20.3 [range: 0–86]
at day 40; P < 0.001), burning (superficial)
spontaneous pain (mean score, 5.6 [range,
0–10] at baseline versus 2.9 [range, 0–10] at
day 40; P < 0.001), pressing (deep) sponta-
neous pain (mean score, 3.5 [range, 0–10] at
baseline versus 1.8 [range, 0–9.5] at day 40;
P < 0.001), paroxysmal pain (mean score,
4.3 [range, 0–9.5] at baseline versus 2.0
[range, 0–9.5] at day 40; P < 0.001),
evoked pain (mean score, 2.3 [range, 0–
8.7] at baseline versus 1.5 [range, 0–6.3] at
Table 1. Baseline demographic and clinical char-
acteristics in 72 adult patients with painful diabetic
neuropathy scheduled to receive 600 mg/day
a-lipoic acid, orally, for 40 days.
Characteristic Value
Age, years 65.2 8.4
Sex, male 28 (38.9)
Body mass index, kg/m2 31.3 5.4
Type 1 diabetes mellitus 11 (15.3)
Type 2 diabetes mellitus 61 (84.7)
Duration of diabetes, years 12.7 8.8
Systolic blood pressure, mmHg 134.2 13.9
Diastolic blood pressure, mmHg 75.8 9.6
Heart rate, beats/min 73.8 10.3
Glycosylated haemoglobin HbA1c, % 7.8 1.9
Estimated glomerular
filtration rate, ml/min/1.73 m2
75.3 21.2
Location of
neuropathic symptoms*
Foot 67 (93.1)
Calves 17 (23.6)
Thigh 8 (11.1)
Medical history*
Coronary artery disease 12 (16.7)
Stroke 6 (8.3)
Peripheral vascular disease 33 (45.8)
Diabetic nephropathy 13 (18.1)
Retinopathy 14 (19.4)
Fasting glucose, mg/dl 141.4 53.7
Total cholesterol, mg/dl 190.4 24.7
Triglycerides, mg/dl 146.8 73.4
High density lipoprotein
cholesterol, mg/dl
49.7 9.6
Low density lipoprotein
cholesterol, mg/dl
110.6 17.4
Data presented as mean SD or n (%) patient prevalence. *
More than one answer is possible in these items.
Table 2. Baseline medications of 72 adult patients
with painful diabetic neuropathy scheduled to
receive 600 mg/day a-lipoic acid, orally, for 40 days.
Treatment type Prevalence
Diabetes treatment*
Insulin 56 (77.8)
Biguanide 46 (63.9)
Dipeptidyl peptidase
4-inhibitor
22 (30.6)
Sulfonylurea 11 (15.3)
Glinide 1 (1.4)
Glucagon-like protein-1
receptor agonist
4 (5.6)
Pioglitazone 3 (4.2)
Sodium-glucose
co-transporter 2 inhibitors
1 (1.4)
Other treatment*
Statin 50 (69.4)
Fibrate 8 (11.1)
Antihypertensive 60 (83.3)
Antiplatelet therapy 45 (62.5)
Medication for painful
neuropathy*
Pregabalin 18 (25.0)
Gabapentin 8 (11.1)
Paracetamol 3 (4.2)
Duloxetine 2 (2.8)
Data presented as n (%) patient prevalence. *
Patients may receive more than one medication.
1784 Journal of International Medical Research 46(5)
day 40; P < 0.001), and paraesthesia/dyses-
thesia (mean score, 5.9 [range, 0–10] at
baseline versus 3.0 [range, 0–10] at day 40;
P < 0.001). Statistically significant reduc-
tions were also evident in the SDS score
between the baseline and day 40 visit, in
terms of work disability score, social life
disability score, and family life disability
score (P < 0.001; Figure 1).
Lastly, PGI-I at the day 40 visit revealed
that 36 patients (50%) rated their health
condition as ‘very much better’ or ‘much
better’. No change was reported by 14
patients (19.4%), and none of the patients
reported worsening of symptoms.
In terms of laboratory parameters,
mean fasting triglyceride levels were signif-
icantly reduced during the a-lipoid acid
Table 3. Baseline and end-of-treatment Subjective Peripheral Neuropathy Screen
Questionnaire responses of 72 adult patients with painful diabetic neuropathy treated with 600
mg/day a-lipoic acid, orally, for 40 days.
Positive response rate
Statistical
significancea Neuropathic symptom Baseline End of treatment
Do you ever have legs and/or feet that
feel numb?
63 (87.5) 30 (41.7) P <0.001
Do you ever have any burning pain in
your legs and/or feet?
60 (83.3) 28 (38.9) P <0.001
Are your feet too sensitive to touch? 26 (36.1) 16 (22.2) P 1⁄4 0.013
Do you get muscle cramps in your legs
and/or feet?
53 (73.6) 20 (27.8) P <0.001
Do you ever have any prickling or tin-
gling feelings in your legs or feet?
56 (77.8) 20 (27.8) P <0.001
Does it hurt at night or when the
covers touch your skin?
26 (36.1) 10 (13.9) P <0.001
When you get into the tub or shower,
are you unable to tell the hot water
from the cold water with your feet?
22 (30.6) 17 (23.6) NS
Do you ever have any sharp, stabbing,
shooting pain in your feet or legs?
47 (65.3) 17 (23.6) P <0.001
Have you experienced an asleep feeling
or loss of sensation in your legs or
feet?
18 (25.0) 5 (6.9) P <0.001
Do you feel weak when you walk? 51 (70.8) 34 (47.2) P <0.001
Are your symptoms worse at night? 48 (66.7) 27 (37.5) P <0.001
Do your legs and/or feet hurt when you
walk?
46 (63.9) 26 (36.1) P <0.001
Are you unable to sense your feet when
you walk?
39 (54.2) 24 (33.3) P <0.001
Is the skin on your feet so dry that it
cracks open?
37 (51.4) 27 (37.5) P 1⁄4 0.002
Have you ever had electric shock-like
pain in your feet or legs?
44 (61.1) 17 (23.6) P <0.001
Data presented as n (%) positive response. a
Statistically significant differences at P < 0.05 (McNemar’s test).
NS, no statistically significant between group difference (P > 0.05; McNemar’s test).
Agathos et al. 1785
administration (146.8 mg/dl [range, 49–
390 mg/dl] at baseline versus 135.5 mg/dl
[range, 56–337 mg/dl] at day 40;
P 1⁄4 0.004). No statistically significant dif-
ference was found in terms of fasting glu-
cose, total cholesterol, LDL-C, high-density
lipoprotein cholesterol, HbA1c, BMI, arte-
rial blood pressure or heart rate between
the baseline and day 40 visits (data not
shown).
A-lipoic acid was well tolerated, no patient
discontinued treatment, and no adverse
events were noted during the 40-day treat-
ment period.
Discussion
The aim of the current study was to
prospectively investigate the effects of
a-lipoic acid on neuropathic symptoms, lab-
oratory parameters and overall quality of
life in patients with diabetic neuropathy.
Treatment with 600 mg/day a-lipoic acid,
orally for 40 days was found to be
Table 4. Baseline and end-of-treatment douleur neuropathique (DN)4 ques-
tionnaire responses of 72 adult patients with painful diabetic neuropathy treated
with 600 mg/day a-lipoic acid, orally, for 40 days.
Positive response rate [see
Statistical
significancea
Pain
characteristic Baseline
End of
treatment
Burning 57 (79.2) 24 (33.3) P <0.001
Painful cold 22 (30.6) 13 (18.1) P 1⁄4 0.012
Electric shock 43 (59.7) 17 (23.6) P <0.001
Tingling 61 (84.7) 33 (45.8) P <0.001
Pins and needles 62 (86.1) 26 (36.1) P <0.001
Numbness 62 (86.1) 31 (43.1) P <0.001
Itching 22 (30.6) 12 (16.7) P 1⁄4 0.006
Hypoesthesia to touch 31 (43.1) 19 (26.4) P 1⁄4 0.002
Hypoesthesia to prick 29 (40.3) 15 (20.8) P <0.001
The pain is caused or
increased by brushing
22 (30.6) 10 (13.9) P <0.001
Data presented as n (%) positive response. a
Statistically significant differences (P < 0.05; McNemar’s test).
Figure 1. Sheehan Disability Scale scores of 72
adult patients with painful diabetic neuropathy
treated with 600 mg/day a-lipoic acid, orally, for 40
days; Data presented as mean SD; P < 0.001
between baseline and day 40 visit for all compari-
sons (Student’s t-test).
1786 Journal of International Medical Research 46(5)
associated with a clinically significant and
prompt reduction in neuropathy symptoms
and an overall improvement in patients’
quality of life. Indeed, treated patients
noted significant improvements in neuro-
pathic symptoms, indicated by reduced
NSS, SPNSQ, and DN4 questionnaire
scores following 40 days of treatment with
a-lipoic acid compared with baseline scores.
Importantly, the patients noted an overall
improvement in quality of life, which was
reflected by the reduction in pain severity
and pain interference in terms of BPI
scores; total score, burning spontaneous
pain, pressing spontaneous pain, paroxysmal
pain, evoked pain, and paraesthesia/dyses-
thesia in NPSI scores; and work disability
score, social life disability score, and family
life disability score in the SDS. In addition,
fasting triglyceride levels were significantly
reduced during the 40-day period. The over-
all treatment demonstrated an excellent
safety profile. It remains to be determined
if the improvement of neuropathy symptoms
could be further enhanced by treatment pro-
longation beyond 40 days and more impor-
tantly if this will have an impact on the long-
term course of diabetic neuropathy per se.
A-lipoic acid, an essential co-enzyme for
energy production in mitochondria, demon-
strates substantial antioxidant properties
and an effect on whole-body physiology.23
A-lipoic acid is found in very low quantities
in almost all foods, and is used as a dietary
supplement and a pharmaceutical agent.24
A-lipoic acid is well absorbed, diffuses
efficiently in both extra-cellular and intra-
cellular spaces, and penetrates the blood-
brain barrier.25 It has been used in several
oxidative-stress models such as diabetes,
ischemia-reperfusion injury, cataract, and
neurodegenerative disorders, as well as in
mushroom and heavy metal poisoning.
Adverse events of a-lipoic acid may include
nausea, vomiting and mild skin reactions.25
A meta-analysis of four clinical trials
comprising 1 258 patients with diabetic
neuropathy (a-lipoic acid-treated group,
716 patients; placebo group, 542 patients)
showed a favourable effect for 600 mg/day
a-lipoic acid, administered i.v., for three
weeks.26 In particular, the relative differ-
ence between baseline and the end of the
three-week treatment was 24.1% for Total
Symptom Score (a composite score of all
neuropathic symptoms), and 16.0% for
Neuropathy Impairment Score.26 In addi-
tion, the responder rates were 52.7%
( 50% improvement in Total Symptom
Score) in the a-lipoic acid-treated group
compared with 36.9% in the placebo
group (P < 0.05).26 This meta-analysis
showed a clear reduction in pain, burning,
paraesthesia, and numbness in the a-lipoic
acid-treated group,26 and no difference in
terms of adverse events and overall safety
was noted between the two groups.
Moreover, another meta-analysis of 15 ran-
domized controlled trials involving patients
with diabetic peripheral neuropathy showed
that treatment with 300–600 mg/day a-lipoic
acid, i.v. for 2–4 weeks was statistically supe-
rior to the control group for increasing
median and peroneal motor nerve conduc-
tion velocity and median and peroneal sen-
sory nerve conduction velocity.13
The pathogenesis of diabetic neuropathy
remains largely unknown. Metabolic and
vascular defects, under increased oxidative
stress, are both implicated in nerve injury in
patients with diabetes.7,13 The rationale for
improvement in neuropathic symptoms in
patients with diabetes, following treatment
with a-lipoic acid, most probably relies on
its antioxidant action. A-lipoic acid, and its
reduced form, dihydrolipoic acid, act as
antioxidants through neutralization of a
variety of reactive oxygen species, inhibition
of reactive-oxygen generators, and repair of
damage caused by other oxidants.23,24 The
antioxidant action of a-lipoic acid may also
contribute to the clinically-significant subsi-
dence of neuropathic symptoms through
improvement in nerve blood flow.27
Agathos et al. 1787
Moreover, a-lipoic acid may interact with
other antioxidants or contribute additively
to the antioxidant effect through different
parameters.25 A recent study compared the
effects of 300 mg/day a-lipoic acid for
90 days with two other antioxidants,
namely omega 3 fatty acids and vitamin E,
in patients with type 2 diabetes mellitus.28 In
this study, significant improvements were
found in all treatment groups in parameters
of oxidative stress, insulin resistance, BMI,
waist circumference, and total cholesterol
levels.28
Evidence-based clinical indications for
administration of a-lipoic acid include
migraine and chronic pain. In patients suf-
fering from migraines, 600 mg/day a-lipoic
acid, administered orally for three months,
showed a statistically significant reduction
in the number, duration and severity of
migraine crises per month, and an overall
response rate of 30%, while these outcomes
remained unchanged in the placebo
group.29 In patients with peripheral neuro-
pathic sciatic pain caused by herniated disc,
600 mg/day a-lipoic acid for 60 days signif-
icantly improved signs and symptoms and
electromyography findings compared with
1180 mg/day acetyl-L-carnitine. In addition,
more patients receiving a-lipoic acid than
acetyl-L-carnitine reported a reduced need
for analgesics (71% versus 45.5%;
P 1⁄4 0.05).30 Similar results have been noted
with 600 mg/day a-lipoic acid in patients
with lower back pain and chronic cervical
pain, and with 300 mg/day a-lipoic acid in
patients with carpal tunnel syndrome.31–33
Clear advantages of the current study
include its prospective design and the very
high precision with the specific sample size.
Moreover, the study was a conducted in a
single centre, thus limiting the possibility of
between-centre variability, as noted by
others.26 This was an open-label study,
however, without a placebo treatment arm,
and as such has inherent limitations, since
both the study participants and the health-
care providers were aware of the treatment
provided. Thus, imagined or random effects
of the agent cannot be ruled out.
Furthermore, it is unclear if and at what
extent the recorded benefits in the present
study group would subside after a-lipoic
discontinuation.
In conclusion, the current study suggests
that 600 mg/day a-lipoic acid, administered
orally for 40 days, to patients with painful
diabetic neuropathy, has a clinically signif-
icant impact on controlling neuropathy
symptoms, fasting triglycerides, and quality
of life. Moreover, half of the treated
patients rated their health status as ‘much
better’ or ‘very much better’ following 40
days of treatment. The current findings sug-
gest that a-lipoic acid is beneficial and thus
should be considered for routine adminis-
tration in patients with diabetes and periph-
eral neuropathy. Whether the recorded
improvements could be augmented further
by prolongation of a-lipoic acid administra-
tion beyond 40 days, or if a-lipoic acid
could decelerate the course of neuropathy
in the long-term, remains to be determined.
Acknowledgements
Nevralip RetardVR
tablets were kindly provided
by Medical Pharmaquality, Athens, Greece.
Declaration of conflicting interests
The authors declare that there is no conflict of
interest.
Funding
This research received no specific grant from any
funding agency in the public, commercial, or
not-for-profit sectors.
ORCID iD
Anastasios Tentolouris http://orcid.org/0000-
0001-5897-472X
1788 Journal of International Medical Research 46(5)
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