Topical rubefacients for acute and chronic pain in adults

Filling data gap for nicotinic acid, nicotinate esters and nicotinamide for the determination of permitted daily exposure by a category approach

This study aimed to obtain necessary toxicological data using experimental and computational methods for the calculation of a common permitted daily exposure (PDE) which can be relevant for nicotinic acid and its esters and nicotinamide according to European Medicines Agency Guideline on setting health-based exposure limits. PDE calculation is mainly based on critical toxicological endpoints. During this procedure, critical toxicological endpoints data of an active pharmaceutical ingredient (API) may not be able to find satisfactorily. Hence, using toxicological data for another API that has a similar chemical structure can be a useful way. In this study, toxicological endpoints of nicotinic acid and its esters and nicotinamide were evaluated. Then, the data gaps in the toxicological endpoints were filledusing the read-across approach. Based on the current existing data, nicotinic acid and its esters and also nicotinamide are not genotoxic and do not have skin sensitization potential. These compounds do not present a concern for carcinogenicity and developmental/reproductive toxicity. Based on these critical endpoints and available experimental data, the final PDE of 10 mg/day was calculated for all category members. Our study showed the utility of the read-across for PDE calculation of APIs with experimental toxicological data gap.

Use of Camphor and Essential Oil Balms for Infants in Cambodia

Balms and oils containing terpenic compounds, such as camphor, menthol and eucalyptus, are potentially toxic, and numerous reports of adverse events stemming from their use in infants and young children have been published. During qualitative research on newborn practices in rural Cambodia, these products were found to be commonly applied to the skin of newborns and infants and available in most households. Parents and caregivers of infants in Cambodia and other settings where use of camphor- and menthol-containing products are common should be educated on the risks of these to prevent child morbidity and potential mortality.

Skin Matters: A Review of Topical Treatments for Chronic Pain. Part Two: Treatments and Applications

In Part One of this two-part series, we discussed skin physiology and anatomy as well as generalities concerning topical analgesics. This modality of therapy has lesser side effects and drug-drug interactions, and patients tolerate this form of therapy better than many oral options. Unfortunately, this modality is not used as often as it could be in chronic pain states, such as that from neuropathic pain. Part Two discusses specific therapies, local anesthetics, and other drugs, as well as how a clinician might use specific aspects of a patient's neuropathic pain presentation to help guide them in the selection of a topical agent.

Salicylate-containing rubefacients for acute and chronic musculoskeletal pain in adults

BACKGROUND

Rubefacients containing salicylates cause irritation of the skin and are believed to relieve various musculoskeletal pains. They are available on prescription, and are common components in over-the-counter remedies. This is an update of a review of rubefacients for acute and chronic pain, originally published in 2009, which found limited evidence for efficacy.

OBJECTIVES

To assess the efficacy and safety of topically applied salicylates in acute and chronic musculoskeletal pain in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and EMBASE, from inception to 22 August 2014, together with the Oxford Pain Relief Database, two clinical trial registries, and the reference lists of included studies and relevant reviews.

SELECTION CRITERIA

Randomised, double-blind, placebo- or active-controlled clinical trials of topical rubefacients containing salicylates to treat musculoskeletal pain in adults, with at least 10 participants per treatment arm, and reporting outcomes at close to 7 (minimum 3, maximum 10) days for acute conditions and 14 (minimum 7) days or longer for chronic conditions.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, and extracted data. We calculated risk ratio (RR) and number needed to treat to benefit or harm (NNT or NNH) with 95% confidence intervals (CI) using a fixed-effect model. We analysed acute and chronic conditions separately.

MAIN RESULTS

New searches for this update identified one new study that satisfied our inclusion criteria, although it contributed information only for withdrawals. Six placebo- and one active-controlled studies (560 and 137 participants, respectively) in acute pain, and seven placebo- and three active-controlled studies (489 and 182 participants, respectively) in chronic pain were included in the review. All studies were potentially at risk of bias, and there were substantial differences between studies in terms of the participants (for example the level of baseline pain), the treatments (different salicylates combined with various other potentially active ingredients), and the methods (for example the outcomes reported). Not all of the studies contributed usable information for all of the outcomes sought.For the primary outcome of clinical success at seven days in acute conditions (mostly sprains, strains, and acute low back pain), the RR was 1.9 (95% CI 1.5 to 2.5) and the NNT was 3.2 (2.4 to 4.9) for salicylates compared with placebo, but this result was not robust (very low quality evidence). Using a random-effects model for analysis the RR was 2.7 (1.05 to 7.0). For the same outcome in chronic conditions (mostly osteoarthritis, bursitis, and chronic back pain), the RR was 1.6 (1.2 to 2.0) and the NNT was 6.2 (4.0 to 13) (very low quality evidence). This result was not substantially changed using a random-effects model for analysis. In both categories there were a number of factors might have influenced the results but sensitivity analysis was limited because of the small number of studies and participants.For both acute and chronic painful conditions any evidence of efficacy came from the older, smaller studies, while the larger, more recent studies showed no effect.Adverse events were more common with salicylate than with placebo but most of the events occurred in only two studies. There was no difference when these studies were removed from the analysis (very low quality evidence). Local adverse events (at the application site) were again more common with salicylate but were nearly all in one study (in which salicylate was combined with another irritant). There was no difference when this study was removed (very low quality evidence).There were insufficient data to draw conclusions against active controls.

AUTHORS' CONCLUSIONS

The evidence does not support the use of topical rubefacients containing salicylates for acute injuries or chronic conditions. They seem to be relatively well tolerated in the short-term, based on limited data. The amount and quality of the available data mean that uncertainty remains about the effects of salicylate-containing rubefacients.

AMPK: An emerging target for modification of injury-induced pain plasticity

Chronic pain is a critical medical problem afflicting hundreds of millions of people worldwide with costly effects on society and health care systems. Novel therapeutic avenues for the treatment of pain are needed that are directly targeted to the molecular mechanisms that promote and maintain chronic pain states. Recent evidence suggests that peripheral pain plasticity is promoted and potentially maintained via changes in translation control that are mediated by mTORC1 and MAPK pathways. While these pathways can be targeted individually, stimulating the AMPK pathway with direct or indirect activators achieves inhibition of these pathways via engagement of a single kinase. Here we review the form, function and pharmacology of AMPK with special attention to its emerging role as a potential target for pain therapeutics. We present the existing evidence supporting a role of AMPK activation in alleviating symptoms of peripheral nerve injury- and incision-induced pain plasticity and the blockade of the development of chronic pain following surgery. We argue that these preclinical findings support a strong rationale for clinical trials of currently available AMPK activators and further development of novel pharmacological strategies for more potent and efficacious manipulation of AMPK in the clinical setting. Finally, we posit that AMPK represents a unique opportunity for drug development in the kinase area for pain because it is pharmacologically manipulated via activation rather than inhibition potentially offering a wider therapeutic window with interesting additional pharmacological opportunities. Altogether, the physiology, pharmacology and therapeutic opportunities surrounding AMPK make it an attractive target for novel intervention for chronic pain and its prevention.

Risk evaluation and mitigation strategies for older adults with persistent pain

The U.S. Food and Drug Administration issued Risk Evaluation and Mitigation Strategies for certain analgesic agents, but all medicines for older adults warrant risk-reduction considerations. Although not all older adults have pain, a higher prevalence of persistent pain exists in this population. Nursing actions are needed to minimize the negative impact persistent pain, analgesic agents, or both have on physical, mental, and social functioning. Practices vary considerably, ranging from failing to use analgesic agents for older adults with considerable pain to exposing them to potentially life-threatening toxicities, overdoses, or drug interactions. Older adults tend to be more vulnerable to side effects and drug interactions due to differences in drug distribution, metabolism, and elimination; thus, vigilant assessment and monitoring is needed to mitigate risks whenever analgesic agents are used. This review delineates these vulnerabilities while informing clinicians of the strategies needed to promote safe, effective use of medications when treating pain in older adults.

Topical NSAIDs for chronic musculoskeletal pain in adults

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly taken orally, but they are also available in topical preparations to be applied to or rubbed onto the skin of a painful joint, typically one affected by arthritis, with the aim of relieving pain locally. Topical NSAIDs are widely used in some parts of the world for acute and chronic painful conditions, but have not been universally accepted until recently. One of the problems has been that older clinical studies were generally short, lasting four weeks or less, and short duration studies are not regarded as adequate in ongoing painful conditions.

OBJECTIVES

To examine the use of topical NSAIDs in chronic musculoskeletal pain, focusing on studies of high methodological quality, and examining the measured effect of the preparations according to study duration. The principal aim was to estimate treatment efficacy in longer duration studies of at least 8 weeks.

SEARCH METHODS

A series of electronic searches, together with bibliographic searches, and searches of in-house databases were combined with electronic searches of clinical trial registers and manufacturers of topical NSAIDs, or companies known to be actively researching topical NSAIDs. There had to be at least 10 participants in each treatment arm, with application of treatment at least once daily.

SELECTION CRITERIA

Randomised, double blind studies with placebo or active comparators, where at least one treatment was a topical NSAID product, in any topical formulation (cream, gel, patch, solution), in studies lasting at least two weeks.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and validity, and extracted data. Numbers of participants achieving each outcome were used to calculate relative risk (RR) and numbers needed to treat (NNT) or harm (NNH) compared to placebo or other active treatment.

MAIN RESULTS

Information was available from 7688 participants in 34 studies from 32 publications; 23 studies compared a topical NSAID with placebo. Topical NSAIDs were significantly more effective than placebo for reducing pain due to chronic musculoskeletal conditions. The best data were for topical diclofenac in osteoarthritis, where the NNT for at least 50% pain relief over 8 to 12 weeks compared with placebo was 6.4 for the solution, and 11 for the gel formulation. There were too few data of good quality to calculate NNTs for other individual topical NSAIDs compared with placebo. Direct comparison of topical NSAID with an oral NSAID did not show any difference in efficacy. There was an increase in local adverse events (mostly mild skin reactions) with topical NSAIDs compared with placebo or oral NSAIDs, but no increase in serious adverse events. Gastrointestinal adverse events with topical NSAID did not differ from placebo, but were less frequent than with oral NSAIDs.A substantial amount of data from unpublished studies was unavailable. Much of this probably relates to formulations that have never been marketed.

AUTHORS' CONCLUSIONS

Topical NSAIDs can provide good levels of pain relief; topical diclofenac solution is equivalent to that of oral NSAIDs in knee and hand osteoarthritis, but there is no evidence for other chronic painful conditions. Formulation can influence efficacy. The incidence of local adverse events is increased with topical NSAIDs, but gastrointestinal adverse events are reduced compared with oral NSAIDs.

A randomized, placebo-controlled double-blinded comparative clinical study of five over-the-counter non-pharmacological topical analgesics for myofascial pain: single session findings

OBJECTIVES

To investigate the effects of topical agents for the treatment of Myofascial Pain Syndrome (MPS) and Myofascial Trigger Point (MTRP).

METHODS

Subjects with an identifiable trigger point in the trapezius muscle, age 18-80 were recruited for a single-session randomized, placebo-blinded clinical study. Baseline measurements of trapezius muscle pressure pain threshold (PPT: by pressure algometer) along with right and left cervical lateral flexion (rangiometer) were obtained by a blinded examiner. An assessor blinded to the outcomes assessments applied one of 6 topical formulations which had been placed in identical plastic containers. Five of these topicals were proposed active formulations; the control group was given a non-active formulation (PLA). Five minutes after the application of the formula the outcome measures were re-tested. Data were analyzed with a 5-way ANOVA and Holms-adjusted t-tests with an alpha level of 0.05.

RESULTS

120 subjects were entered into the study (63 females; ages 16-82); 20 subjects randomly allocated into each group. The pre- and post-treatment results for pressure threshold did show significant intra-group increases for the Ben-Gay Ultra Strength Muscle Pain Ointment (BG), the Professional Therapy MuscleCare Roll-on (PTMC roll-on) and Motion Medicine Cream (MM) with an increased threshold of 0.5 kg/cm2 (+/-0.15), 0.72 kg/cm2 (+/-0.17) and 0.47 Kg/cm2 (+/-0.19) respectively. With respect to the inter-group comparisons, PTMC roll-on showed significant increases in pressure threshold compared with Placebo (PLA) (p = 0.002) and Icy Hot Extra Strength Cream (IH) (p = 0.006). In addition, BG demonstrated significant increases in pressure threshold compared with PLA (p = 0.0003).

CONCLUSIONS

With regards to pressure threshold, PTMC roll-on, BG and MM showed significant increases in pain threshold tolerance after a short-term application on a trigger points located in the trapezius muscle. PTMC roll-on and BG were both shown to be superior vs placebo while PTMC was also shown to be superior to IH in patients with trigger points located in the trapezius muscle on a single application.CMCC Research Ethics Board Approval # 1012X01, 2011.

Evaluation of a novel topical essential oxygen oil for the treatment of pain in acute tendinopathy and sprains

Topical analgesics may play an increasingly important role in managing acute and chronic pain as acetaminophen, NSAIDs, and opioid drugs come under heightened scrutiny. This article reviews studies about essential oxygen oil, a topical over-the-counter (OTC) analgesic new to the American market but available for many years in Europe. Prospective studies evaluating the oil's safety and efficacy in acute and chronic pain patients, a dermatological study in which healthy subjects served as their own controls, and a post-marketing surveillance study were considered. These studies found the novel essential oxygen oil to be safe and effective in a variety of acute and chronic pain syndromes as well as being well tolerated with few side effects. Its mechanism of action is not understood and further study is warranted. Essential oxygen oil is safe and effective for the treatment of pain associated with many common conditions, including tendinopathy, arthritis, sprains, and others.

Topical NSAIDs for acute pain in adults

BACKGROUND

Use of topical NSAIDs to treat acute musculoskeletal conditions is widely accepted in some parts of the world, but not in others. Their main attraction is their potential to provide pain relief without associated systemic adverse events.

OBJECTIVES

To review the evidence from randomised, double-blind, controlled trials on the efficacy and safety of topically applied NSAIDs in acute pain.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, The Cochrane Library, and our own in-house database to December 2009. We sought unpublished studies by asking personal contacts and searching on-line clinical trial registers and manufacturers web sites.

SELECTION CRITERIA

We included randomised, double-blind, active or placebo (inert carrier)-controlled trials in which treatments were administered to adult patients with acute pain resulting from strains, sprains or sports or overuse-type injuries (twisted ankle, for instance). There had to be at least 10 participants in each treatment arm, with application of treatment at least once daily.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and validity, and extracted data. Numbers of participants achieving each outcome were used to calculate relative risk and numbers needed to treat (NNT) or harm (NNH) compared to placebo or other active treatment.

MAIN RESULTS

Forty-seven studies were included; most compared topical NSAIDs in the form of a gel, spray, or cream with a similar placebo, with 3455 participants in the overall analysis of efficacy. For all topical NSAIDs combined, compared with placebo, the number needed to treat to benefit (NNT) for clinical success, equivalent to 50% pain relief, was 4.5 (3.9 to 5.3) for treatment periods of 6 to 14 days. Topical diclofenac, ibuprofen, ketoprofen, and piroxicam were of similar efficacy, but indomethacin and benzydamine were not significantly better than placebo. Local skin reactions were generally mild and transient, and did not differ from placebo. There were very few systemic adverse events or withdrawals due to adverse events. There were insufficient data to reliably compare individual topical NSAIDs with each other or the same oral NSAID.

AUTHORS' CONCLUSIONS

Topical NSAIDs can provide good levels of pain relief, without the systemic adverse events associated with oral NSAIDs, when used to treat acute musculoskeletal conditions.

Increased prevalence of metabolic syndrome in individuals with osteoarthritis: an analysis of NHANES III data

BACKGROUND

Osteoarthritis (OA) and cardiovascular disease (CVD) share age and obesity as risk factors, but may also be linked by pathogenic mechanisms involving metabolic abnormalities and systemic inflammation. This study compared the prevalence of OA and metabolic syndrome (MetS) in subjects with OA versus the general population without OA to determine whether having OA predicts increased cardiovascular risk.

METHODS

National Health and Nutrition Examination Survey III data were used as a representative sample of the general US population. Subjects included adults aged > or = 18 years with records of history, physical, radiographic, and laboratory data adequate to assess for diagnoses of MetS and OA. Logistic regression was used to examine the association between MetS and population-weighted variables.

RESULTS

The general population sample included 7714 subjects (weighted value representing 174.9 million population), of whom 975 subjects had OA (weighted value 17.5 million) and 6739 did not (weighted value 157.4 million). Metabolic syndrome was prevalent in 59% of the OA population and 23% of the population without OA. Each of the 5 cardiovascular risk factors that comprise MetS was more prevalent in the OA population versus the population without OA: hypertension (75% vs 38%), abdominal obesity (63% vs 38%), hyperglycemia (30% vs 13%), elevated triglycerides (47% vs 32%), and low high-density lipoprotein cholesterol (44% vs 38%). Metabolic syndrome was more prevalent in subjects with OA regardless of sex or race. The association between OA and MetS was greater in younger subjects and diminished with increasing age. Having OA at age 43.8 years (mean age of the general population) was associated with a 5.26-fold (SE = 1.58, P < 0.001) increased risk of MetS. This association remained strong when obesity was controlled for in additional regression models.

CONCLUSIONS

Osteoarthritis is associated with an increased prevalence of MetS, particularly in younger individuals. Global cardiovascular risk should be assessed in individuals aged < or = 65 years with OA, and should be considered when prescribing analgesics for OA patients.

Acute back pain: benefits and risks of current treatments

OBJECTIVE

To review the efficacy and safety of current treatments for acute low back pain.

RESEARCH DESIGN AND METHODS

PubMed was searched for clinical trials in which the words, acute, back, and pain all appeared in the study summary. The search was from the earliest references included in this database (1949) until 1 May 2009. This resulted in retrieval of 129 papers. Review of study summaries indicated that 36 provided information about either a topical treatment or oral therapy for acute low back pain. In addition, studies included as part of the evidence base for the Evidence Review of American Pain Society/American Academy of Pain Medicine Evidence Review for Evaluation and Management of Low Back Pain were reviewed.

RESULTS

Recommended topical and systemic pharmacologic treatments for acute low back pain include application of superficial heat, acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), skeletal muscle relaxants/benzodiazepines, and opioids including tramadol. Only a small number of studies compared different approaches to treatment of acute back pain and most failed to demonstrate significant differences among treatments. Available results support the view that both NSAIDs and low-level continuous heat treatment are more effective than acetaminophen and that heat treatment is also significantly more effective than ibuprofen. A potential limitation of this study is that information from trials published in journals not included in PubMed or reported only at meetings and not yet published was not included.

CONCLUSIONS

A wide range of treatments is currently recommended for the management of patients with acute back pain and all are supported by results from controlled clinical trials.