Topical application of doxepin hydrochloride can reduce the symptoms of complex regional pain syndrome: a case report

Topical Treatments for Localized Neuropathic Pain

Purpose of Review

Topical therapeutic approaches in localized neuropathic pain (LNP) syndromes are increasingly used by both specialists and general practitioners, with a potentially promising effect on pain reduction. In this narrative review, we describe the available compounds for topical use in LNP syndromes and address their potential efficacy according to the literature.

Recent Findings

Local anaesthetics (e.g., lidocaine, bupivacaine and mepivacaine), as well as general anaesthetic agents (e.g., ketamine), muscle relaxants (e.g., baclofen), capsaicin, anti-inflammatory drugs (e.g., diclofenac), salicylates, antidepressants (e.g., amitriptyline and doxepin), α2 adrenergic agents (e.g., clonidine), or even a combination of them have been tested in various applications for the treatment of LNP. Few of them have reached a sufficient level of evidence to support systematic use as treatment options.

Summary

Relatively few systemic side effects or drug–drug interactions and satisfactory efficacy seem to be the benefits of topical treatments. More well-organized and tailored studies are necessary for the further conceptualization of topical treatments for LNP.

Alternative methods of pain management for the older adult population: Review of topical pain medications

The older adult population is one of the fastest growing age groups in the United States. As this population continues to expand, determining the safest way to provide pain management has become increasingly important. More than 50% of community-dwelling older adults experience pain on a daily basis, and up to 83% of those in assisted living facilities experience persistent pain. Pain is exceedingly challenging to treat safely and effectively in the elderly because of the physiologic changes that occur as people age. In addition, many nonnarcotic medications with analgesic properties are listed in both the 2012 American Geriatrics Society Beers Criteria for Potentially Inappropriate Medication Use in Older Adults and the Pharmacy Quality Alliance high-risk medications lists. An approach to the growing challenge of managing pain in the elderly that is gaining popularity among community-dwelling patients is the use of topical pain medications. The goal of this article is to review some of the available literature regarding the use of various topical analgesics alone or in combination, and to discuss their known or theoretical mechanisms of peripheral pain modulation. Commercially available or compounded topical pain medications may be used to replace or augment doses of oral medications in an effort to decrease the risk of adverse drug events for older adult patients. When prescribing topical pain medications physicians should consider the nature of the pain targeted, the type of analgesia expected from each ingredient, the potential for systemic absorption, and related side effects.

Alternate Routes of Administration of Antidepressant and Antipsychotic Medications

Objective: To review the administration of antidepressant and antipsychotic medications via inhaled, intranasal, buccal, sublingual, transdermal, and rectal routes. Data Sources: A PubMed search was conducted for all data through March 31, 2015 to identify pertinent literature. Search terms included the generic name of each antidepressant and antipsychotic medication in combination with the following terms: alternate routes of administration, inhaled, intranasal, buccal, sublingual, transdermal, and rectal. Study Selection and Data Extraction: English-language case reports, studies, and reviews describing medication administration in human subjects were included. Data Synthesis: Commercially available products that use an alternative route of administration include loxapine for inhalation, asenapine for sublingual administration, and selegiline for transdermal administration. Case reports and studies describe intranasal, sublingual, and transdermal routes of administration of antipsychotic medications as well as buccal, sublingual, transdermal, and rectal administration of antidepressant medications. The concordance between the physicochemical properties possessed by some antipsychotic and antidepressant agents and the physicochemical properties required for nontraditional routes of administration suggest that administration via alternative routes may be feasible for some of these drugs. Further exploration of drug absorption via alternative routes in addition to consideration of patient and formulation factors may yield improvements in medication therapy for patients with psychiatric illnesses. Conclusions: For patients unable to tolerate oral or injectable therapy, administration of psychotropic medications via nontraditional routes may be feasible. The development of alternative routes of drug delivery could prevent discontinuation of needed medication therapy.

A randomized, prospective study of efficacy and safety of oral tramadol in the management of post-herpetic neuralgia in patients from north India

OBJECTIVE

To evaluate the safety and efficacy of oral tramadol therapy (50 to 200 mg/day) in the treatment for post-herpetic neuralgia (PHN).

METHODS

The study was a prospective, single-blind, non-responder vs. responder, randomized trial conducted in 100 outpatients of PHN after oral administration of tramadol for 4 weeks. Those patients who had achieved 50% or greater pain relief after 14 days of oral tramadol treatment were categorized as responders and those reporting < 50% pain relief were categorized as non-responders. Rescue analgesia was provided by the topical application of a cream consisting of the combination of 3.33% doxepin and 0.05% capsaicin to the affected areas of PHN patients of both groups for at least 14 days, along with tramadol therapy. The rescue analgesia was extended to 4 weeks in patients of the non-responder group. The primary endpoints were measured using a numerical rating scale (NRS) at rest and with movement. Secondary endpoints included additional pain ratings such as global perceived effect (GPE), Neuropathic Pain Symptom Inventory scores (NPSI), daily sleep interference score (DSIS), quality of life (QOL) as per WHO QOL-BREF Questionnaire scores, patient and clinician ratings of global improvement. The 2 groups were compared on the basis of pain intensity scores, encompassing primary as well as secondary endpoints, and QOL after 28 days of the treatment regimen.

RESULTS

Pain intensity scores measured by NRS (at resting and with movement), NPSI, and DSIS were consistently reduced (P < 0.001) over 28 days at varying intervals in both the groups, but the magnitude of reduction was higher in responders than non-responders. A concomitant improvement (P < 0.001) was observed in GPE on days 3, 14, and 28 as compared to the respective baseline scores in both the groups. Although the WHO QOL-BREF scores showed significant (P < 0.001) improvement in QOL of PHN patients at days 14 and 28 in both the groups, the magnitude of improvement was higher in responders as compared to non-responders. Significant improvement in pain intensity scores and QOL in non-responders is mainly attributed to the use of rescue analgesia for 28 days rather than recommended tramadol therapy.

CONCLUSIONS

Treatment with tramadol 50 to 200 mg per day was associated with significant pain reduction in terms of enhanced pain relief, reduced sleep interference, greater global improvement, diminished side-effect profile, and improved QOL in PHN patients from North India. Further categorization of PHN patients may be helpful so that additional or alternative therapy may be prescribed to non-responders.

Pain management in older people

At times providing pain relief in elderly patients can prove troublesome. Their tolerance and perception of pain can differ from that of younger patients, while the incidence of pain is above that found in those of less advanced years.

Conventional approaches to providing pain relief can be successful, but the tolerance to the side-effects of those drugs used to provide pain relief can be less. Furthermore, polypharmacy can have implications for the range of analgesic drugs that can be considered. Fortunately there are an increasing range of medicinal products with reduced potential for side-effects that can be considered when treating older patients with pain.

Ameliorating effect of capsaicin on alterations in lipid metabolism during mice lung carcinoma

Spices and vegetables possess antioxidant activity that can be applied for preservation of lipids and lower lipid peroxidation in biological systems. In the present study, we have investigated the effect of capsaicin on lipid metabolism during benzo(a)pyrene induced lung cancer in Swiss albino mice. Benzo(a)pyrene (50 mg/kg wt) induced lung cancer animals showed abnormal changes in the tissue and serum lipids, lipoproteins and lipid metabolizing enzymes. Treatment with capsaicin (10 mg/kg body wt) remarkably attenuated all the above alterations and restored normalcy. These findings reveal the chemomodulatory potential of capsaicin in attenuating the alterations in lipid metabolism during experimental lung carcinogenesis.

Topical analgesic agents

Pain processing and transmission are achieved by a complex interaction of pathways and processes. Those parts of the process with peripheral representation may be amenable to therapeutic intervention by systemic administration to achieve a peripheral effect or by local application, including local topical administration to the skin overlying the painful area. Advantages include high level of patient acceptance, ease of administration, avoidance of systemic side effects, and reduced drug-drug interactions. Those drugs with topical analgesic effects include those with specific topical analgesic indication and others in which no such indication exists but that may offer a chance of pain therapy at reduced risk.

Antidepressants as analgesics

Depression is a common accompaniment of pain, particularly when pain is unremitting. The use of a variety of antidepressant medications is associated with pain reduction, an effect that is independent of the mood-enhancing qualities of these drugs. This pain relief is a consequence of a wide variety of actions of antidepressants on the neuroregulatory mechanisms associated with pain perception and transmission. The older tricyclic antidepressants (TCAs) and the newer 'balanced' reuptake inhibitors (such as duloxetine) seem to be more efficacious in terms of providing pain relief than the selective serotonin reuptake inhibitors (SSRIs). Unfortunately, adverse effects are not uncommon during antidepressant use, particularly with TCAs. It is now becoming apparent that TCAs can have an analgesic effect when applied topically and that this effect is produced by peripheral mechanisms rather than systemic uptake. Antidepressants remain a major therapeutic tool in the management of chronic pain.

Topical analgesics

Historically, analgesics were applied by the topical route of administration. With the advent of oral formulations of drugs, topical application became less popular among physicians, although patients still rated this method of drug delivery as efficacious and practical. We now appreciate that peripheral mechanisms of actions of a variety of preparations rationalizes their topical application and gives further opportunity to target peripheral receptors and neural pathways that previously required systemic administration to achieve therapeutic effect. Therefore, a peripheral effect can be generated by using locally applied drug and, consequently, systemic concentrations of that drug may not reach the level at which systemic side effects can occur.

Novel therapeutic usage of low-dose doxepin hydrochloride

Low-dose doxepin hydrochloride (1, 3 and 6 mg) is a tricyclic antidepressant currently being investigated for the treatment of primary insomnia in adult and geriatric patients. Although it has been used at much higher doses to treat depression effectively for a number of decades, it offers a unique potency and selectivity for antagonizing the H1 (histamine) receptor at low doses. This mechanism of action may prove to be advantageous compared with other medications currently approved for the treatment of insomnia. This article reviews previous clinical studies using doxepin for insomnia and the recent clinical trial data, and briefly discusses other potential roles of this compound in clinical practice.

Multimodal approaches to the management of neuropathic pain: the role of topical analgesia

Because of their localized activity and low systemic absorption, topical analgesics have a favorable safety profile and a low risk for drug-drug interactions. There is a growing body of evidence on the efficacy and safety of these agents in a variety of pain disorders, including the most prevalent neuropathic pain conditions. The molecular basis for the usage of peripheral analgesics in neuropathic pain and the available clinical trial evidence for a wide variety of topical agents are reviewed.

Topical analgesics

Our knowledge and understanding of the pathophysiology and treatment of pain is increasing; however, we should not lose sight of the simple opportunities that exist for intercepting pain at peripheral targets. Although systemic medication often has peripheral and central modes of action, the appeal for provision of medication close to where these peripheral targets exist should be high. If these sites can be attacked with relatively high concentrations of active drug while keeping systemic levels of that drug below the level at which systemic side effects become apparent, then this should lead to desirable outcomes. Even though the number of true topical agents with an indication for this use is small, a number of other topical agents are available that evidence suggests have the possibility of being effective. Given the increased understanding of pain, the likelihood of further topical agents becoming available is high.

The pharmacotherapy of chronic pain: a review

The past two decades have contributed a large body of preclinical work that has assisted in our understanding of the underlying pathophysiological mechanisms that cause chronic pain. In this context, it has been recognized that effective treatment of pain is a priority and that treatment often involves the use of one or a combination of agents with analgesic action. The current review presents an evidence-based approach to the pharmacotherapy of chronic pain. Medline searches were done for all agents used as conventional treatment in chronic pain. Published papers up to June 2005 were included. The search strategy included randomized, controlled trials, and where available, systematic reviews and meta-analyses. Further references were found in reference sections of papers located using the above search strategy. Agents for which there were no controlled trials supporting efficacy in treatment of chronic pain were not included in the present review, except in cases where preclinical science was compelling, or where initial human work has been positive and where it was thought the reader would be interested in the scientific evidence to date.

Pharmacological strategies in relieving neuropathic pain

The pharmacological treatment of neuropathic pain relies, to a large extent, on drugs belonging to a small number of defined classes. Opioids, tricyclic antidepressants, antiepileptic drugs and membrane stabilisers form the current basis of treatment. Varying levels of evidence support the use of individual members of these classes and overall show no indication that one class of drug, or individual drug has universal effectiveness. More refined knowledge of the modes of action of these agents used to treat neuropathic pain should lead to a more logical approach to the management of this difficult series of conditions. A number of drugs currently licensed for a different indication have recently had an analgesic effect in neuropathic pain attributed to them. In addition, a number of novel compounds are undergoing investigation and provide hope of dicovering more efficacious treatment options in the future.

Pharmacological management of neuropathic pain

In health, the nervous system exists in a balance between inhibitory and excitatory influences. This balance may be upset if neural tissue is damaged or irritated and may give rise to neuropathic pain. Such neuropathic pain does not respond consistently to opioid analgesics or NSAIDs and it may therefore be necessary to utilise other therapeutic agents with known activity on either the excitatory or inhibitory components of the pain pathway. These other agents are traditionally considered with reference to their original uses; we still refer to tricyclic antidepressants (TCAs) and anticonvulsant drugs when a consideration of their modes of action may allow more rational use. For example, carbamazepine is related to the TCAs by virtue of its chemical structure and proposed mode of action and yet is still classified as an anticonvulsant drug. With respect to the opioids, increasing evidence points to an analgesic effect in neuropathic pain, although concerns regarding tolerance and dependence still prevent more widespread use. The anticonvulsants comprise a group of compounds possessing anticonvulsant and analgesic properties, but each possesses differing modes of action and so several members of the class should be tried before a conclusion is reached that they, as a whole, are ineffective. TCAs may also have a role in the treatment of neuropathic pain. As with all drugs, if their use is not associated with pain relief in a defined period of time, their use should be terminated. Topical TCAs may also have a role where the area of neuropathic pain is small. Other options, such as SSRIs, membrane stabilisers, capsaicin, baclofen and clonidine may have potential in treating neuropathic pain. The available evidence regarding the efficacy of currently available agents for the treatment of neuropathic pain is sparse. With the knowledge of achieving analgesia, according to the modes of actions of various agents it is hoped that the treatment of this difficult condition may be more logical and successful.

Topical application of the tricyclic antidepressant doxepin can reduce dysuria and frequency

The aim of this article is to highlight a novel treatment for the symptoms of chronic urethral and trigonal irritation. A patient with severe urethral hyperaesthesia who derived almost complete alleviation of symptoms with topical application of a tricyclic antidepressant cream is described. The possible modes of action of tricyclics when used via the topical route of administration are described. Topical application of a tricyclic antidepressant cream may alleviate the symptoms of urethral hyperaesthesia.