Neuropathic pain is the most common type of
pain in neuropathy. In painful
polyneuropathies the
pain usually has a "glove and stocking" distribution. The
pain may be predominantly spontaneous, e.g., with a burning, pricking, or shooting character or characterized by evoked
pain such as mechanical or cold
allodynia. In the clinical setting, the prevention of painful neuropathies and treatment of underlying neuropathy remains inadequate and thus symptomatic treatment of the
pain and related disability needs to be offered. Most randomized, double-blind, placebo-controlled trials (RCTs) published in
painful neuropathy have been conducted in patients with diabetes and to what extent a treatment which is found effective in painful
diabetic polyneuropathy can be expected to relieve other conditions like
chemotherapy- or HIV-induced neuropathy is unknown.
Tricyclic antidepressants (TCAs),
gabapentin,
pregabalin, and
serotonin noradrenaline reuptake inhibitors (
SNRIs) are first
drug choices. In patients with localized
neuropathic pain, a topical
lidocaine patch may also be considered. Second-line treatments are
tramadol and other
opioids. New types of treatment include
botulinum toxin type A (BTX-A), high-dose
capsaicin patches, and
cannabinoids. Other types of
anticonvulsant drugs such as
lamotrigine,
oxcarbazepine, and
lacosamide have a more questionable efficacy in painful
polyneuropathy but may have an effect in a subgroup of patients. Combination
therapy may be considered in patients with insufficient effect from one
drug. Treatment is usually a trial-and-error process and has to be individualized to the single patient, taking into account all comorbidities such as possible concomitant depression, anxiety, diseases, and drug interactions. Side-effects to
antidepressants include dry mouth,
nausea,
constipation,
orthostatic hypotension, and sedation. ECG should always be obtained prior to treatment with TCAs, which also should not be used in patients with cardiac incompensation and
epilepsy. The most common side-effects of
gabapentin and
pregabalin are CNS-related side-effects with
dizziness and
somnolence. Peripheral
edema,
weight gain,
nausea,
vertigo,
asthenia, dry mouth, and
ataxia may also occur. Topical treatments are better tolerated due to lack of systemic side-effects but there is still limited evidence for the long-term efficacy of these drugs. With available drugs, the average
pain reduction is about 20-30%, and only 20-35% of the patients will achieve at least 50%
pain reduction, which stresses the need of a multidisciplinary approach to
pain treatment.