Topical analgesics for neuropathic pain in the elderly: current and future prospects

Pulsed radiofrequency alleviates neuropathic pain by upregulating MG53 to inhibit microglial activation

BACKGROUND

Patients with neuropathic pain (NP) have significantly lower quality of life. Because the pathophysiology of NP is not fully understood, there is a lack of effective treatment for it in clinic. This study set out to investigate the precise mechanism by which pulsed radiofrequency (PRF) alleviated NP.

METHOD

The rat models of chronic constriction injury of the sciatic nerve (CCI) were established to simulate the occurrence of NP, following with measuring MWT and TWL to evaluate the pain of the rats. HE staining was utilized to observe the rat spinal cord tissue pathology. The expression of MG53, ATF4 and CHOP was evaluated by qRT-PCR and WB, while the expression of inflammatory factors was measured by ELISA. In addition, immunofluorescence assay was used to detect the expression of MG53 and Iba-1.

RESULT

PRF treatment alleviated NP in CCI rats, as well as upregulating the expression of MG53 and inhibiting microglial activation. After MG53 knockdown, the remission of NP by PRF was significantly weakened, but microglial activation and endoplasmic reticulum stress (ERS) exhibited enhancement. Therefore, PRF inhibited microglial activation by upregulating MG53. After injection of ERS inducer in CCI rats, the inhibition effect of overexpressed MG53 on microglial activation and its alleviation effect on NP were reversed. Consequently, MG53 played a role in suppressing microglial activation by mediating the inhibition of ERS.

CONCLUSION

PRF attenuated microglial activation by upregulating MG53 to inhibit ERS, resulting in the alleviation of NP in CCI rats.

Successful treatment of notalgia paresthetica with lidocaine 5% medicated plaster: a case report

Notalgia paresthetica (NP) is a sensory neuropathy characterized by chronic, localized pruritus in a circumscribed area on the upper back. Pruritus, frequently resistant to treatment, may be accompanied by pain, paresthesia, allodynia and alloknesis. There is a paucity of data in the NP literature about the use of lidocaine 5% medicated plaster. This case involves a 75-year-old woman with NP and a history of many unsuccessful local or systemic treatments. The patient was treated with lidocaine 5% medicated plaster, while other therapies were progressively retired. After 11 weeks of therapy, a significant reduction in the intensity of itching was achieved and the itching area was reduced. The patient also reported an associated improvement in her quality of life throughout therapy. In conclusion, lidocaine 5% medicated plaster was successful in relieving itching and other symptoms in this case of NP.

Topical Capsaicin for the Treatment of Neuropathic Pain

BACKGROUND

Neuropathic pain (NP) is an egregious problem worldwide. Due to the side-effects of oral drugs, drugs delivered directly to the affected area of pain are preferred.

OBJECTIVE

Capsaicin, a chemical compound isolated from chili peppers, is used as an analgesic in topical ointments and dermal patches to alleviate pain. Objective of the study is to review the application and functionality of topical capsaicin in treatment of neuropathic pain.

DATA SOURCES

To systematically review capsaicin's functions on NP, we retrieved articles from the PubMed database published in the last ten years.

STUDY ELIGIBILITY CRITERIA

The inclusion criteria were capsaicin and the use of capsaicin for the treatment of NP; on the other hand, articles were excluded according to the mentioned criteria such as abstracts, articles written in any language other than English, incomplete articles, and conference papers.

PARTICIPANTS AND INTERVENTIONS

Out of 265 articles, 108 articles were selected after filtering through the inclusion and exclusion criteria. The data and knowledge currently existing for capsaicin treatment in NP are summarized.

RESULTS

This review indicates that capsaicin effectively improves NP treatment without affecting the motor and large nerve fibres involved in sensory function. Transient receptor potential channel vanilloid type 1 (TRPV1) is the capsaicin receptor expressed in central and peripheral terminals of a sensitive primary nerve cell. Conclusions and implications of key findings: Topical capsaicin has a sensible safety profile and is effective in reducing NP. Therefore, studies over the last decade suggest that capsaicin might be a potential drug for NP treatment.

Topical Treatment of Localized Neuropathic Pain in the Elderly

The prevalence of neuropathic pain in the older population has been reported to be very high and is most commonly localized to a circumscribed area. Treatment failure is frequent in neuropathic pain and is accompanied by central side effects with recommended oral drugs acting on the central nervous system. A number of topical pharmaceuticals are available on prescription and also sold over the counter. This review in persons aged older than 60 years shows the efficacy of lidocaine 5% and capsaicin 8% for localized neuropathic pain while results with other pharmaceuticals are rather inconsistent. Local application of drugs has a very limited systemic effect and the pharmacological advantages of local over systemic treatment are particularly interesting in older persons who often have comorbidities and take multiple medications. However, more information is needed on the efficacy and safety of lidocaine 5% and capsaicin 8% in older old persons and on the long-term effects of these pharmaceuticals. These studies should also pave the way for research and development in the field of topical analgesics with a satisfactory level of evidence-based medicine.

[Pain in old age]

The prevalence of chronic pain increases with increasing age. Multimorbidity increases the risk of disease-related pain. Addressing the problem of pain in higher age is concerned with an increasing problem of care. The multimorbidity and the resulting multimedication are important for the medical care of pain. The therefore necessary physician-patient verbal communication can hardly be remunerated and carried out in the current care landscape. Existing resources must be bundled. The quality of life of older people and not the absence of pain, must be emphasized. Particularly problematic is the recognition and treatment of pain in patients with dementia. Pain in dementia patients is more rarely detected. In addition to questioning relatives and caregivers, a structured pain interview is necessary. The pharmacology of chronic pain is concerned above all with the prevention of iatrogenic risks through interactions and pharmacological complications. The patient-related treatment priorities must be checked and adjusted during the course of treatment. To be considered are age-related altered metabolic pathways. A sensible therapy option is the training of physical activity with a positive effect on the entire pain experience. Behavioral medical treatment procedures are other important building blocks in pain therapy. In addition to the multimodal therapeutic approaches, a stronger interdisciplinary collaboration of special pain medicine and geriatrics is necessary.

Treatment of postherpetic neuralgia with 5% lidocaine medicated plaster in elderly patients - subgroup analyses from three European clinical trials

OBJECTIVE

To investigate short- and long-term effectiveness and safety of the 5% lidocaine medicated plaster in the treatment of postherpetic neuralgia (PHN) in elderly patients (≥70 years of age).

METHODS

Data from three European clinical trials was compared after stratification according to age (<70 years and ≥70 years). Length of study phase investigated was 4 weeks for study 1, 8 weeks for study 2, and up to 12 months for study 3. Effectiveness outcome measures were pain intensity, pain relief, allodynia severity, Clinical Global Impression of Change, and Patient Global Impression of Change. Safety was assessed by adverse event documentation.

RESULTS

Mean average pain intensity improved in the elderly by -2.1 (SD 2.1) vs. -2.5 (SD 2.0) for <70 year old patients after 4 weeks, by -1.4 (SD 1.8) vs. -1.7 (SD 1.3) after 8 weeks, and by -1.5 (SD 1.9) vs. -2.7 (SD 2.2) after 12 months. Most patients presented with allodynia (>85% of elderly, >78% of younger patients) which was described by >51% as painful or extremely painful. Allodynia severity was markedly reduced in both groups during all three trials. Drug-related adverse events occurred in <20% of elderly and <15% of <70 year old patients and were mainly skin related.

CONCLUSIONS

The 5% lidocaine medicated plaster provided pain relief and marked reductions in allodynia severity in elderly PHN patients with an excellent safety profile under short- and long-term treatment supporting the addition of the plaster to the treatment armamentarium for this age group.

STUDY LIMITATIONS

All analyzed study phases were open-label and lacking a placebo control group.

Skin matters! The role of keratinocytes in nociception: a rational argument for the development of topical analgesics

Treatment of neuropathic pain using topical formulations is still in its infancy. Only few topical analgesic formulations have become available for clinical use, and among these, analgesic creams are still rare. This is unfortunate because analgesic creams offer a number of advantages over patches, such as convenience, ease of adapting the frequency of application, and dose, and “rubbing cream where it hurts” involves the patient much more in the therapeutic process compared to patches and other localized treatment modalities. Although the literature supporting the efficacy and safety of analgesic creams (mostly compounded) is growing since the last decade, most pain physicians have not yet noticed and appreciated the therapeutic potential and clinical value of these creams. This is most probably due to a prejudice that topical application should need to act transdermally, more or less as a slow-release formulation, such as in patches delivering opioids. We will discuss this prejudice and show that there are multiple important targets in the skin to be reached by topical analgesic or anti-inflammatory compounds, and that the keratinocyte is one of those targets. By specifically targeting the keratinocyte, analgesia seems possible, effective, and safe, and thus topical analgesic creams may hold promise as a novel treatment modality for neuropathic pain.

Pretreatmet with 5% lidocaine patch reduces cannula-induced and propofol-induced pain: a randomized, double-blind, placebo-controlled study

Background

The purpose of this study was to determine the efficacy of 5% lidocaine patch in reducing propofol-induced pain and cannula-induced pain.

Methods

In a randomized, double-blind study, 126 patients were divided into one of three groups: pretreatment with a 5% lidocaine patch (Lidotop®) and premixed 2 ml of normal saline with 1.5 mg/kg of 1% propofol (Group A); pretreatment with a placebo patch and premixed 2 ml of normal saline with 1.5 mg/kg of 1% propofol (Group B); or pretreatment with a placebo patch and premixed 2 ml of 2% lidocaine (40 mg) with 1.5 mg/kg of 1% propofol (Group C) for induction of anesthesia. Pain severity was evaluated on a four-point verbal rating scale during intravenous cannulation, propofol injection, and 24 h after the operation (recall).

Results

Eighteen patients (47.4%) in Group A complained of cannula-induced pain compared with 35 (94.6%) in Group B and 36 (94.7%) in Group C (P < 0.001). Group A patients showed significantly lower incidence of propofol-induced pain and recall of propofol-induced pain compared with Group B (P < 0.001 and P = 0.01), whereas there was no difference compared with Group C.

Conclusions

Preoperative transdermal administration of 5% lidocaine patch is an effective and simple method in reducing propofol-induced pain as well as cannula-induced pain.

Neuropathic Pain Among Community-Dwelling Older People: A Clinical Study in Finland

BACKGROUND

Neuropathic pain is more common among older people than in the general population, and the efficacy of medical treatment often remains unsatisfactory.

OBJECTIVE

The aim of this study was to assess the presence, diagnostic certainty, etiology and treatment of neuropathic pain in community-dwelling older people with chronic pain.

METHODS

Independently living older people aged 75, 80 and 85 years subject to communal preventive home visits with chronic pain were invited to a clinical pain examination by a geriatrician.

RESULTS

Overall, 106 patients consented to participate in the clinical study. Neuropathic pain was diagnosed in 51 (48%) patients, with 75% of pain states definite and 25% probable neuropathic pain. The most common etiology was degenerative disease of the spinal column causing radiculopathy. At the study visit, 11 patients (22% of neuropathic pain patients) were receiving medication that was demonstrated to be effective against neuropathic pain. The geriatrician recommended a trial of a new medicine for 17 patients, but only six continued the medication going forward.

CONCLUSIONS

Neuropathic pain was surprisingly common in our cohort. Finding effective pain medication is challenging due to comorbidities, possible side effects, and vulnerability in older age. Other pain management methods should be considered.