EMLA cream in the treatment of post-herpetic neuralgia. Efficacy and pharmacokinetic profile

Use of EMLA as an adjunct for burning pain associated with a liposarcoma

Objective. To report the successful use of EMLA cream (a topical anesthetic) for the relief of neuro pathic pain in a patient with a liposarcoma.

Case Summary. A 63-year-old male with a lipo sarcoma was admitted to the hospital to establish an effective pain control regimen. Despite the use of high-dose hydromorphone, dexamethasone, and in domethacin, he still complained of a burning sensa tion in the skin over the tumor site. EMLA—applied regularly every 8 hours, was started, and within 24 hours the patient reported relief from this pain.

Discussion. While there is some experience with the use of systemically administered anesthetics for the control of neuropathic pain in cancer patients, there is little reported experience of the use of topical anesthetics. EMLA has, however, been successfully used for postherpetic neuralgia. Adverse reactions from its use for reducing the pain of venipuncture are usually mild and transient, and repeated use does not appear to increase the risk of toxicity. In this case, the patient's pain was well-controlled without any observ able adverse reactions.

Summary. This patient experienced relief of burning pain when EMLA was added to his treatment regimen. EMLA cream could be considered as a treatment option for cancer patients experiencing neuropathic pain, but the patients most likely to benefit and the optimal treatment regimen have yet to be determined by a prospective study.

Clinical management of pain in advanced lung cancer

Lung cancer is the most common cancer in the world and pain is its most common symptom. Pain can be brought about by several different causes including local effects of the tumor, regional or distant spread of the tumor, or from anti-cancer treatment. Patients with lung cancer experience more symptom distress than patients with other types of cancer. Symptoms such as pain may be associated with worsening of other symptoms and may affect quality of life. Pain management adheres to the principles set out by the World Health Organization's analgesic ladder along with adjuvant analgesics. As pain can be caused by multiple factors, its treatment requires pharmacological and non-pharmacological measures from a multidisciplinary team linked in with specialist palliative pain management. This review article examines pain management in lung cancer.

Herpes zoster ophthalmicus

OPINION STATEMENT

The management of herpes zoster (HZ) usually involves a multidisciplinary approach aiming to reduce complications and morbidity. Patients with herpes zoster ophthalmicus (HZO) are referred to ophthalmologists for prevention or treatment of its potential complications. Without prompt detection and treatment, HZO can lead to substantial visual disability. In our practice, we usually evaluate patients with HZO for corneal complications such as epithelial, stromal, and disciform keratitis; anterior uveitis; necrotizing retinitis; and cranial nerve palsies in relation to the eye. These are acute and usually sight-threatening. We recommend oral acyclovir in conjunction with topical 3% acyclovir ointment, lubricants, and steroids for conjunctival, corneal, and uveal inflammation associated with HZO. Persistent vasculitis and neuritis may result in chronic ocular complications, the most important of which are neurotrophic keratitis, mucus plaque keratitis, and lipid degeneration of corneal scars. Postherpetic complications, especially postherpetic neuralgia (PHN), are observed in well over half of patients with HZO. The severe, debilitating, chronic pain of PHN is treated locally with cold compresses and lidocaine cream (5%). These patients also receive systemic treatment with NSAIDs, and our medical colleagues cooperate in managing their depression and excruciating pain. Pain is the predominant symptom in all phases of HZ disease, being reported by up to 90% of patients. Ocular surgery for HZO-related complications is performed only after adequately stabilizing pre-existing ocular inflammation, raised intraocular pressure, dry eye, neurotrophic keratitis, and lagophthalmos. Cranial nerve palsies are common and most often involve the facial nerve, although palsy of the oculomotor, trochlear, and abducens nerves may occur in isolation or (rarely) simultaneously. In our setting, complete ophthalmoplegia is seen more often than isolated palsies, but recovery is usually complete. Vasculitis within the orbital apex (orbital apex syndrome) or brainstem dysfunction is postulated to be the cause of cranial nerve palsies. A vaccine of a lyophilized preparation of the oka strain of live, attenuated varicella-zoster virus is suggested for patients who are at risk of developing HZ and has been shown to boost immunity against HZ virus in older patients.

Lidocaine eye drops attenuate pain associated with ophthalmic postherpetic neuralgia

BACKGROUND

Topical lidocaine (LDC) treatment using a gel or patch preparation is effective in the treatment of postherpetic neuralgia (PHN), but neither is suited for the eye in patients with ophthalmic PHN. Herein, we examined the effect of LDC 4% eye drops on ophthalmic PHN pain.

METHODS

Twenty-four patients with ophthalmic PHN were randomized to receive 0.4 mL eye drops of either LDC 4% or saline placebo (PBO) in the painful eye. After a 7-day period, the patients were crossed over to receive the alternative eye drops. The pain in the eye and the forehead was assessed with a visual analog scale (VAS) before and 15 minutes after treatment. Patients used a descriptive scale to grade pain outcome and were asked to note whether the pain returned and how long after therapy it recurred.

RESULTS

LDC significantly decreased the VAS score of persistent pain in the eye (baseline: 5.9 +/- 2.2 cm; 15 minutes after eye drops: 0.9 +/- 1.8 cm, mean +/- SD [P < 0.01]) and in the forehead (baseline: 6.3 +/- 2.0 cm; 15 minutes after eye drops: 2.6 +/- 2.7 cm [P < 0.01]). The delta change in these VAS scores between LDC and PBO was significant (P < 0.01). Moreover, pain was described as moderate or better by 23 patients after they received LDC and 4 patients of the PBO group. The effect of LDC persisted for a median of 36 hours (range, 8-96 hours) after application.

CONCLUSIONS

This study suggests that LDC provides a significant improvement of ophthalmic PHN because of its prompt analgesia, lack of systemic side effects, and convenience of use.

Efficacy of a metered-dose 8% lidocaine pump spray for patients with post-herpetic neuralgia

OBJECTIVE

Topical lidocaine patch is effective in the treatment of post-herpetic neuralgia (PHN), but not suited for paroxysmal pain because of the long latency of analgesia. Here, we examined the efficacy of 8% lidocaine pump spray (Xylocaine pump spray, XPS) for PHN.

DESIGN

Twenty-four patients with PHN were recruited into a randomized, double-blind, placebo-controlled, crossover study (study 1), and 100 patients with PHN were recruited into an open-labeled study (study 2). In study 1, patients were randomized to receive either XPS or saline placebo pump spray (PPS) applied to the painful skin areas. Following a 7-day period, patients were crossed over to receive the alternative treatment. In study 2, XPS was prescribed for patients who were advised to use the spray anytime, with a 2-hour gap between applications, for 2 weeks. The pain was assessed with a visual analogue scale (VAS). Details of use were noted in the diary.

RESULTS

In study 1, greater decreases in VAS of persistent pain followed application of XPS (baseline: 6.1 +/- 1.7 cm, 15-minute post-spray: 2.3 +/- 2.5 cm, mean +/- SD) than with PPS (6.1 +/- 1.7 cm, 5.7 +/- 1.6 cm, [P < 0.01]). The effect persisted for a median of 4.5 hours (range, 2 to 24 hours) after application. In study 2, 13 of 100 patients discontinued the treatment because of mild local side effects or insufficient effect. In the remaining 87 patients, XPS maintained significant pain relief relative to baseline throughout the 2-week period. Satisfaction with the therapy was reported by 79% of patients.

CONCLUSIONS

In both studies, XPS provided a significant improvement in PHN due to its prompt analgesia, lack of systemic side effects, and convenience of use.

Postherpetic Neuralgia: The Never-Ending Challenge

Postherpetic neuralgia (PHN) is defined as pain that persists 1 to 3 months following the rash of herpes zoster (HZ). PHN affects about 50% of patients over 60 years of age and 15% of all HZ patients. Patients with PHN may experience two types of pain: a steady, aching, boring pain and a paroxysmal lancinating pain, usually exacerbated by contact with the involved skin. Herpes zoster is initially a clinical diagnosis, based on the observation of a typical dermatomal distribution of rash and radicular pain. HZ is pathologically characterized by inflammatory necrosis of dorsal root ganglia, occasionally associated with evidence of neuritis, leptomeningitis, and segmental unilateral degeneration of related motor and sensory roots. Although acyclovir has been used successfully as standard therapy for varicella zoster virus (VZV) infection in the past decade, resistant strains of VZV are often recognized in immunocompromised patients. Therapy with acyclovir and the use of corticosteroids have been reported to prevent PHN in up to 60% of HZ patients. Management of chronic pain in PHN is more problematic. The only therapy proven effective for PHN in controlled study is the use of tricyclic antidepressants, including amitriptyline and desipramine. There is good evidence of efficacy from randomized trials that gabapentin and pregabalin (new anticonvulsant drugs) are of benefit in the reduction of pain from PHN. As alternative therapies, topical agents such as capsaicin, lidocaine or opioid analgesic treatment may give satisfactory results. Interventions with low risk, such as transcutaneous electrical nerve stimulation (TENS), are appropriate. Evidence is scant for the value of surgical and procedural interventions in general, although there are numerous, small studies supporting the use of specific interventions such as nerve blocks, neurosurgical procedures, and neuroaugmentation. Although antiviral agents are appropriate for acute HZ, and the use of neural blockade and sympathetic blockade may be helpful in reducing pain in selected patients with HZ, there is little evidence that these interventions will reduce the likelihood of developing PHN. Postherpetic neuralgia remains a difficult pain problem. This review describes the epidemiology and pathophysiology of PHN and discusses proposed mechanisms of pain generation with emphasis on the various pharmacological treatments and invasive modalities currently available.

Analgesic therapy in postherpetic neuralgia: a quantitative systematic review

BACKGROUND

Postherpetic neuralgia (PHN) is a complication of acute herpes zoster, which is emerging as a preferred clinical trial model for chronic neuropathic pain. Although there are published meta-analyses of analgesic therapy in PHN, and neuropathic pain in general, the evidence base has been substantially enhanced by the recent publication of several major trials. Therefore, we have conducted a systematic review and meta-analysis for both efficacy and adverse events of analgesic therapy for PHN.

METHODS AND FINDINGS

We systematically searched databases (MEDLINE 1966-2004, EMBASE 1988-2004, CINAHL 1982-2002, and PubMed [29 October 2004]) for trials of PHN. We also searched references of retrieved studies and review articles for further trials. We included trials that examined adult patients with PHN of greater duration than 3 mo, that were blinded, randomised, and had at least one measure of pain outcome. Dichotomous pain outcome data were extracted for 50% decrease in baseline pain using a hierarchy of pain/pain-relief measurement tools. Where available, dichotomous data were also collected for adverse events. Calculated estimates of efficacy included relative benefit and number needed to treat. Of 62 studies identified, 35 were randomised controlled trials. Of these, 31 were placebo controlled and suitable for meta-analysis, from which it was possible to extract dichotomous efficacy outcome data from 25. This meta-analysis revealed that there is evidence to support the use of the following orally administered therapies: tricyclic antidepressants, "strong" opioids, gabapentin, tramadol, and pregabalin. Topical therapies associated with efficacy were lidocaine 5% patch and capsaicin. Finally, a single study of spinal intrathecal administration of lidocaine and methyl prednisolone demonstrated efficacy, although this has yet to be replicated. Data suggest that the following therapies are not associated with efficacy in PHN: certain NMDA receptor antagonists (e.g., oral memantine, oral dextromethorphan, intravenous ketamine), codeine, ibuprofen, lorazepam, certain 5HT1 receptor agonists, and acyclovir. Topical administration of benzydamine, diclofenac/diethyl ether, and vincristine (iontophoresis) are similarly not associated with efficacy, nor are intrathecal administration of lidocaine alone or epidural administration of lidocaine and methylprednisolone, intravenous therapy with lidocaine, subcutaneous injection of Cronassial, or acupuncture. However, many of the trials that demonstrated a lack of efficacy represented comparatively low numbers of patient episodes or were single-dose studies, so it may be appropriate to regard such interventions as "not yet adequately tested" rather than demonstrating "no evidence of efficacy." Topical aspirin/diethyl ether has not been adequately tested.

CONCLUSION

The evidence base supports the oral use of tricyclic antidepressants, certain opioids, and gabapentinoids in PHN. Topical therapy with lidocaine patches and capsaicin is similarly supported. Intrathecal administration of methylprednisolone appears to be associated with high efficacy, but its safety requires further evaluation.

Relief of pain in acute herpes zoster by nerve blocks and possible prevention of post-herpetic neuralgia

PURPOSE

This report describes two cases of acute herpes zoster (AHZ) treated by nerve block resulting in immediate pain relief and possible prevention of post-herpetic neuralgia (PHN).

CLINICAL FEATURES

Two elderly females with AHZ of cervical dermatomes and severe pain received deep cervical and greater occipital nerve blocks with a local anesthetic, epinephrine and steroid. In both patients, pain resolved immediately and permanently (one year follow-up) after a single treatment. Case #1: A 79-yr-old female with a mechanical mitral valve and anticoagulated with warfarin presented with AHZ of 17 days duration of the right C2, 3, 4 dermatomes and severe pain. A stellate ganglion block was not performed because of anticoagulation. Rather, a deep cervical root block at C3 and a greater occipital nerve block were performed with bupivacaine, epinephrine and methylprednisolone. No adverse events were evident. Case #2: A 73-yr-old female with a history of osteoarthritis and Meniere's disease presented with AHZ of seven days duration of the left C2, 3, 4 dermatomes and severe pain. Deep cervical root blocks at C3 and C4 and a greater occipital nerve block were performed with bupivacaine, epinephrine and methylprednisolone. Side effects of dizziness, hoarseness, hypertension and Horner's syndrome resolved in a few hours. A mild sensation of itching persisted for two weeks.

CONCLUSION

This report illustrates the potential of nerve blocks in severe AHZ to treat acute pain and possibly prevent PHN.

Skin infections in the elderly

The diagnosis and management of viral diseases of the skin are significant issues in the elderly population. With advances in these areas, there are new tools to combat these diseases and limit morbidity. It is important for clinicians to monitor and treat these diseases aggressively in the elderly because of the potential for immunosuppression in this population. Further advances in antiviral therapy and the potential for the development of antiviral vaccines will aid in the therapy of these diseases. Onychomycosis is found more frequently in the elderly. In this population, the most common clinical presentations are distal and lateral subungual onychomycosis (which usually affects the great or first toe) and white superficial onychomycosis (which generally involves the third or fourth toes). Over the past several years, new treatments for this disorder have emerged that offer shorter courses of therapy and greater efficacy than previous therapies. The treatment of bacterial skin and skin structure infections in the elderly is an important issue. There has been an alarming increase in the incidence of gram-positive infections, including resistant bacteria, such as MRSA and drug-resistant pneumococci. Although vancomycin has been considered the drug of last defense against gram-positive multidrug-resistant bacteria, the late 1980s saw a rise in vancomycin-resistant bacteria, including VRE. With treatment options limited, it has become critical to identify antibiotics with novel mechanisms of activity. Several new drugs have emerged as possible therapeutic alternatives, including linezolid and quinupristin-dalfopristin.

Cutaneous infections in the elderly: diagnosis and management

Over the past several years there have been many advances in the diagnosis and treatment of cutaneous infectious diseases. This review focuses on the three major topics of interest in the geriatric population: herpes zoster and postherpetic neuralgia (PHN), onychomycosis, and recent advances in antibacterial therapy. Herpes zoster in adults is caused by reactivation of the varicella-zoster virus (VZV) that causes chickenpox in children. For many years acyclovir was the gold standard of antiviral therapy for the treatment of patients with herpes zoster. Famciclovir and valacyclovir, newer antivirals for herpes zoster, offer less frequent dosing. PHN refers to pain lasting > or = 2 months after an acute attack of herpes zoster. The pain may be constant or intermittent and may occur spontaneously or be caused by seemingly innocuous stimuli such as a light touch. Treatment of established PHN through pharmacologic and nonpharmacologic therapy will be discussed. In addition, therapeutic strategies to prevent PHN will be reviewed. These include the use of oral corticosteroids, nerve blocks, and treatment with standard antiviral therapy. Onychomycosis, or tinea unguium, is caused by dermatophytes in the majority of cases, but can also be caused by Candida and nondermatophyte molds. Onychomycosis is found more frequently in the elderly and in more males than females. There are four types of onychomycosis: distal subungual onychomycosis, proximal subungual onychomycosis, white superficial onychomycosis, and candidal onychomycosis. Over the past several years, new treatments for this disorder have emerged which offer shorter courses of therapy and greater efficacy than previous therapies. The treatment of bacterial skin and skin structure infections in the elderly is an important issue. There has been an alarming increase in the incidence of gram-positive infections, including resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and drug-resistant pneumococci. While vancomycin has been considered the drug of last defense against gram-positive multidrug-resistant bacteria, the late 1980s saw an increase in vancomycin-resistant bacteria, including vancomycin-resistant enterococci (VRE). More recently, strains of vancomycin-intermediate resistant S. aureus (VISA) have been isolated. Gram-positive bacteria, such as S. aureus and Streptococcus pyogenes are often the cause of skin and skin structure infections, ranging from mild pyodermas to complicated infections including postsurgical wound infections, severe carbunculosis, and erysipelas. With limited treatment options, it has become critical to identify antibiotics with novel mechanisms of activity. Several new drugs have emerged as possible therapeutic alternatives, including linezolid and quinupristin/dalfopristin.

Review of Lidocaine Patch 5% Studies in the Treatment of Postherpetic Neuralgia

Postherpetic neuralgia (PHN) is a chronic pain syndrome that disproportionately affects the elderly; its incidence is anticipated to increase as the population ages. PHN presents as pain (continuous burning or intense paroxysmal), most often with tactile allodynia, which may be severe and disabling, resulting in poor quality of life and depression. Traditional treatments have included tricyclic antidepressants, anticonvulsants and opioids; however, adverse systemic effects associated with these agents have led to the development of a newer and potentially safer agent, the topical lidocaine patch 5% (Lidoderm), a targeted peripheral analgesic. This article reviews the clinical pharmacology of the lidocaine patch 5% for the treatment of PHN and summarises data from clinical trials of its safety, tolerability and efficacy. The Medline search terms "lidocaine" and "patch" were used to search for English-language articles on the pharmacokinetics of the lidocaine patch 5% and its clinical use for the treatment of PHN. Additional published studies not identified by the database search but performed by the authors or their colleagues were also included in the review. The systemic absorption of lidocaine from the patch was minimal in healthy adults when four patches were applied for up to 24 hours/day, and lidocaine absorption was even lower among PHN patients than healthy adults at the currently recommended dose. Vehicle-controlled and open-label trials found the lidocaine patch 5%, either alone or in combination with other agents, to be effective in the treatment of PHN. Most adverse events were at patch application sites; no clinically significant systemic adverse effects were noted, including when used long term or in an elderly population.In patients with PHN, the lidocaine patch 5% has demonstrated relief of pain and tactile allodynia with a minimal risk of systemic adverse effects or drug-drug interactions. Because of its proven efficacy and safety profile, the lidocaine patch 5% has been recommended as a first-line therapy for the treatment of the neuropathic pain of PHN.

Pressure-pain function in desensitized and hypersensitized muscle and skin assessed by cuff algometry

This study assessed a newly developed cuff pressure algometry during discrete leg skin/muscle sensitization and anesthesia. Experimental setup consisted of a pneumatic tourniquet cuff, a computer-controlled air compressor, and an electronic visual analog scale (VAS). The first experiment assessed cuff algometry before and after selective anesthesia of the skin and the muscle under the cuff. The second experiment assessed cuff algometry before and during skin and muscle sensitization with capsaicin cream and injection of capsaicin. Pressure-pain detection threshold, pressure equivalent to the pain intensity of 2 on the VAS (PVAS2), pressure-pain tolerance threshold, and pressure-pain stimulus-response (SR) function were evaluated. Local anesthesia of the muscle increased the pain thresholds significantly and shifted the average SR function to the right indicating desensitization, whereas cutaneous anesthesia did not affect the pressure thresholds and increased the slope of the SR function. Capsaicin cream did not affect pressure-pain tolerance threshold, whereas PVAS2 and the slope of the SR function were significantly decreased. Intramuscular capsaicin injection decreased the pain thresholds and did not affect the slope of the SR function. Both interventions shifted the SR function to the left. The cuff algometry reliably assessed the pressure-pain SR function during muscle sensitization/desensitization and might supplement conventional pressure algometry for standardized pressure-pain function assessment.

Pharmacological management of postherpetic neuralgia

Postherpetic neuralgia, which occurs most typically in older persons, is one of the most common and serious complications of herpes zoster (or shingles). It is a chronic neuropathic pain syndrome and remains one of the most difficult pain disorders to treat. Known beneficial agents include antidepressants, antiepileptic drugs, opioid analgesics, local anaesthetics, capsaicin and other, less applied, modalities. Although monotherapy is commonly applied, no single best treatment for postherpetic neuralgia has been identified; nevertheless, gabapentin (antiepileptic) and transdermal lidocaine (anaesthetic) are often used as the first-choice treatments. Recent research has shed light on possible pain mechanisms as well as new avenues of treatment, which are discussed in the article. For patients with pain that is not adequately controlled, individualised treatment plans must be pursued. It is critical to recognise that postherpetic neuralgia, while difficult to manage, can be a treatable neuropathic pain syndrome.

Topical and peripherally acting analgesics

Acute nociceptive, inflammatory, and neuropathic pain all depend to some degree on the peripheral activation of primary sensory afferent neurons. The localized peripheral administration of drugs, such as by topical application, can potentially optimize drug concentrations at the site of origin of the pain, while leading to lower systemic levels and fewer adverse systemic effects, fewer drug interactions, and no need to titrate doses into a therapeutic range compared with systemic administration. Primary sensory afferent neurons can be activated by a range of inflammatory mediators such as prostanoids, bradykinin, ATP, histamine, and serotonin, and inhibiting their actions represents a strategy for the development of analgesics. Peripheral nerve endings also express a variety of inhibitory neuroreceptors such as opioid, alpha-adrenergic, cholinergic, adenosine and cannabinoid receptors, and agonists for these receptors also represent viable targets for drug development. At present, topical and other forms of peripheral administration of nonsteroidal anti-inflammatory drugs, opioids, capsaicin, local anesthetics, and alpha-adrenoceptor agonists are being used in a variety of clinical states. There also are some clinical data on the use of topical antidepressants and glutamate receptor antagonists. There are preclinical data supporting the potential for development of local formulations of adenosine agonists, cannabinoid agonists, cholinergic ligands, cytokine antagonists, bradykinin antagonists, ATP antagonists, biogenic amine antagonists, neuropeptide antagonists, and agents that alter the availability of nerve growth factor. Given that activation of sensory neurons involves multiple mediators, combinations of agents targeting different mechanisms may be particularly useful. Topical analgesics represent a promising area for future drug development.

Viral skin infections in the elderly: diagnosis and management

Over the past several years, there have been advances in the diagnosis and treatment of cutaneous viral diseases in elderly patients. Herpes zoster is caused by reactivation in adults of the varicella-zoster virus (VZV) that causes chickenpox in children. For many years, aciclovir was the gold standard of antiviral therapy for the treatment of herpes zoster. Famciclovir and valaciclovir are newer antivirals, which offer less frequent administration. Postherpetic neuralgia (PHN) refers to pain lasting 2 months or more after an acute attack of herpes zoster. The pain may be constant or intermittent. The treatment of established PHN may include topical anaesthetics, analgesics, tricyclic antidepressants and anticonvulsants, and nonpharmacological therapy may be used to complement such treatment. Therapeutic strategies to prevent PHN include the use of oral corticosteroids, nerve blocks, and treatment with standard antiviral therapy. The three most recently discovered human herpes viruses (HHV-6, HHV-7 and HHV-8), in common with the other members of the family, may cause a primary infection, establish latent infection in a specific set of cells in their host, and then reactivate if conditions of altered immunity develop. These viruses have been associated with an array of disorders, which are important for the clinician to recognise. Cytomegalovirus (CMV) is a member of the herpesvirus family that is very prevalent worldwide. More than 80% of primary infections and 20% of reactivation-producing symptoms occur in transplant populations. Treatment options include intravenous administration of ganciclovir, foscarnet or cidofovir. Herpes simplex virus (HSV) most commonly affects the genital and perioral regions. In the elderly, HSV infection is typically manifest at the vermilion border of the lip. The main concern of recurrent herpes labialis in the elderly is related to potential autoinoculation of the eye or genital area. Treatment with aciclovir, famciclovir or valaciclovir is indicated for these infections. Molluscum contagiosum is caused by a poxvirus, which produces cutaneous lesions that appear as small, firm, umbilicated papules. Immunocompromised patients often do not respond to the usual destructive therapies, and intravenous or topical cidofovir may be useful in these patients.

Treatment of postherpetic neuralgia: an update

Postherpetic neuralgia (PHN) is a chronic pain syndrome that is often refractory to treatment and can last for years, causing physical and social disability, psychological distress, and increased use of the healthcare system. In this paper we provide an update on recent developments in the treatment of PHN. We emphasise the results of recent studies that provide an evidence-based approach for treating PHN that was not available until very recently. In randomised, controlled clinical trials, the topical lidocaine patch, gabapentin, and controlled release oxycodone have been shown to provide superior pain relief in patients with PHN when compared with placebo. It has also recently been demonstrated that the tricyclic antidepressant nortriptyline provides equivalent analgesic benefit when compared with amitriptyline, but is better tolerated. Based on these results, nortriptyline can now be considered the preferred antidepressant for the treatment of PHN, although desipramine may be used if the patient experiences unacceptable sedation from nortriptyline. The topical lidocaine patch, gabapentin and controlled release oxycodone all appear to be as effective as tricyclic antidepressants in the treatment of patients with PHN, and the results of these recent studies suggest that each of these treatments should be considered early in the course of treatment. Additional controlled trials are needed to compare the efficacy and tolerability of these 4 treatments- tricyclic antidepressants, gabapentin, the topical lidocaine patch and controlled release opioid analgesics--used singly and in various combinations in the treatment of patients with PHN.

Topical amethocaine (Ametop) is superior to EMLA for intravenous cannulation. Eutectic mixture of local anesthetics

PURPOSE

A eutectic mixture of local anesthetics (EMLA) is commonly used to provide topical anesthesia for intravenous (i.v.) cannulation. One of its side effects is vasoconstriction, which may render cannulation more difficult. A gel formulation of amethocaine (Ametop) is now commercially available. The aim of this study was to compare EMLA and Ametop with regard to the degree of topical anesthesia afforded, the incidence of vasoconstriction and the ease of i.v. cannulation.

METHODS

Thirty two ASA I adult volunteers had a #16 gauge i.v. cannula inserted on two separate occasions using EMLA and Ametop applied in a double blind fashion for topical anesthesia. Parameters that were recorded after each cannulation included visual analogue pain scores (VAPS), the presence of vasoconstriction and the ease of cannulation, graded as: 1 = easy, 2 = moderately difficult, 3 = difficult and 4 = failed.

RESULTS

The mean VAPS +/- SD after cannulation with Ametop M was 12+/-9.9 and with EMLA was 25.3+/-16.6 (P = 0.002). Vasoconstriction occurred after EMLA application on 17 occasions and twice after Ametop (P = 0.001). The grade of difficulty of cannulation was 1.44+/-0.88 following EMLA and 1.06+/-0.25 with Ametop (P = 0.023).

CONCLUSIONS

Intravenous cannulation was less painful following application of Ametop than EMLA. In addition, Ametop caused less vasoconstriction and facilitated easier cannulation. Its use as a topical anesthetic agent is recommended, especially when i.v. access may be problematic.

Postthoracotomy Syndrome and Postherpetic Neuralgia

Postthoractomy syndrome (PTS) is a multifactorial dis ease process which has never been adequately de scribed. This, in turn, has led to a discrepancy in the literature concerning the signs and symptoms which constitute PTS and what are the most efficacious treat ment modalities that should be used. The most impor tant fact before instituting therapy for PTS, is that recurrent disease must be ruled out. Once this is done, a stepped-treatment regimen can be instituted. Postherpetic neuralgia (PHN) is a disease state which afflicts 10% to 15% of patients who become infected with herpes zoster. At this time, there appears to be no definitive treatment regimen for PHN. However, there are various treatment modalities which can signifi cantly decrease the pain associated with the disease. There seem to be many promising agents undergoing scientific trials, so that a definitive treatment for PHN may soon be available.

Efficacy of a eutectic mixture of local anesthetics as a topical anesthetic in minor otologic procedures

A eutectic mixture of local anesthetics (EMLA), prepared as a cream, is an oil-in-water emulsion of 2 anesthetic agents lidocaine and prilocaine. Several clinical applications of EMLA cream, its effectiveness as a topical anesthetic, and its safety profile have been previously reported. We report our experience with EMLA cream in 17 adult and 24 pediatric patients. We find EMLA to be the preferred anesthetic for performing minor outpatient otologic procedures in adults. We also find EMLA to be a safe, well-tolerated alternative to general anesthesia in some pediatric patients. Potential cost savings of EMLA cream during pediatric myringotomies in the clinic are also discussed.

Varicella zoster virus

Because of its ability to produce two clinically distinct disease entities (chickenpox and shingles), varicella zoster virus (VZV) is an unusual etiologic agent. Although in the past viral exanthems were mostly only of academic interest to the practitioner, the development of antiviral agents and the newly approved varicella (OKA) vaccine have increased the clinical significance. Also, with the increasing seroprevalence of HIV infection, more patients will be stricken with zoster (at a younger age) and disseminated varicella. In this review, the history, incidence, pathogenesis, clinical manifestations, and treatment options (of VZV infection and postherpetic neuralgia) will be discussed.

Pain caused by herpes zoster infection

Postherpetic neuralgia (PHN) is a neuropathic pain disorder that occurs most often in the elderly. This painful condition is uniquely suited for clinical research, resulting in an emerging understanding of the pathophysiology of the persistent pain. Until recently, only the tricyclic antidepressants proved effective for PHN. Controlled trials of a wide variety of therapeutic strategies are in progress or have been recently completed.

Jaipur block in postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia, a common sequele to herpes zoster infection, is a chronic debilitating problem. The available therapeutic modalities are usually ineffective.

METHODS

A total of 3960 patients (1326 women and 2634 men; age group, 21-84 years), with postherpetic neuralgia as the presenting complaint and with pain lasting from 2 months to 5 years, were treated with Jaipur block, consisting of local subcutaneous infiltration of 2% xylocaine, 0.5% bupivacaine, and 4 mg/mL dexamethasone solution. Patients were followed up at six-weekly intervals with subsequent injections given in non-responders.

RESULTS

Twenty-eight per cent of patients obtained complete relief from pain after a single injection, another 57% after a second injection, and 11% after a third injection; 4% of patients did not respond to treatment. The non-responders were either old (over 60 years) or had pain lasting for more than 2 years. The response to therapy was similar in both sexes. There were 31 left-handed patients in this study. Pain was less severe in left-handed patients and they obtained complete relief after a single injection. Side-effects including giddiness and sweating were seen, occasionally, in a few patients.

CONCLUSIONS

Ninety six per cent of patients obtained complete relief after the block with a follow-up of up to 19 years.

Current and Future Management of Herpes Zoster

Herpes zoster (shingles) is a common disease affecting approximately three in 1000 of the population per year and up to 10 in 1000 per year in the elderly population. This incidence is likely to increase as the proportion of elderly people in the general population increases and various forms of immunosuppression become more common, e.g. following organ transplantation. Management of both the acute and chronic pain is probably the most important part of caring for shingles patients. Antiviral therapy, anti-inflammatory steroids and sympathetic nerve blocks are the main measures used during the acute phase to prevent the development of postherpetic neuralgia (PHN). Antiviral agents given early in the acute phase of herpes zoster are generally the therapy of choice and there is also growing evidence for benefit with tricyclic antidepressants. Pain relief once PHN has developed is generally much less effective. Many classes of drug have been investigated for the management of PHN and some have been found to be helpful in some patients. There is as yet no generally effective agent, however preventive antiviral therapy early in the course of herpes zoster is recommended for all elderly patients since they have a high risk of developing severe PHN.

Topical aspirin/diethyl ether mixture versus indomethacin and diclofenac/diethyl ether mixtures for acute herpetic neuralgia and postherpetic neuralgia: a double-blind crossover placebo-controlled study

The efficacy of topical aspirin/diethyl ether (ADE) mixture in the treatment of acute herpetic neuralgia and postherpetic neuralgia, suggested in a previous open-label study (De Benedittis et al. 1992), has been evaluated in a double-blind crossover placebo-controlled study as compared with two other NSAID (indomethacin and diclofenac) drug/ether mixtures. The study included 37 patients (15 with acute herpetic neuralgia (AHN) and 22 with postherpetic neuralgia (PHN)). Comparative treatment results showed that only aspirin (but not indomethacin and diclofenac) was significantly superior to placebo, as compared with baseline and duration of pain relief (P < 0.05 and P < 0.01, respectively), in both AHN and PHN groups. Good-to-excellent results were achieved by 87% of AHN patients and by 82% of PHN patients treated with the ADE mixture, with no significant differences between the two groups. On the whole, patients with trigeminal involvement, less severe pain and with dysaesthetic quality of pain yielded best results.

Lidocaine patch: double-blind controlled study of a new treatment method for post-herpetic neuralgia

Post-herpetic neuralgia (PHN) is a common and often intractable neuropathic pain syndrome predominantly affecting the elderly. Topical local anesthetics have shown promise in both uncontrolled and controlled studies. Thirty-five subjects with established PHN affecting the torso or extremities completed a four-session, random order, double-blind, vehicle-controlled study of the analgesic effects of topically applied 5% lidocaine in the form of a non-woven polyethylene adhesive patch. All subjects had allodynia on examination. Up to 3 patches, covering a maximum of 420 cm2, were applied to cover the area of greatest pain as fully as possible. Lidocaine containing patches were applied in two of the four 12-h-long sessions, in one session vehicle patches were applied, and one session was a no-treatment observation session. Lidocaine containing patches significantly reduced pain intensity at all time points 30 min to 12 h compared to no-treatment observation, and at all time points 4--12 h compared to vehicle patches. Lidocaine patches were superior to both no-treatment observation and vehicle patches in averaged category pain relief scores. The highest blood lidocaine level measured was 0.1 micrograms/ml, indicating minimal systemic absorption of lidocaine. Patch application was without systemic side effect and well tolerated when applied on allodynic skin for 12 h. This study demonstrates that topical 5% lidocaine in patch form is easy to use and relieves post-herpetic neuralgia.

Use of EMLA cream in the treatment of post-herpetic neuralgia

EMLA cream is an acronym for eutectic mixture of local anesthetics. It contains lidocaine and prilocaine creams. A eutectic preparation, applied topically, penetrates into the dermis after an application period of 1 to 2 hours. This case report describes the successful treatment with EMLA cream of post-herpetic neuralgia, which was resistant to other modes of therapy, and briefly discusses the pharmacology of EMLA cream.

Adjuvant analgesic agents

Adjuvant analgesics are usually considered when the patient with cancer pain fails to attain a satisfactory balance between analgesia and side effects during opioid therapy, or experiences a comorbid symptom or disorder that may be amenable to one of the adjuvant drugs. When pain is the primary indication, the use of adjuvant analgesics is one strategy that must be evaluated in comparison with other potentially analgesic approaches. The potential costs, inconvenience, and risks associated with polypharmacy must be balanced by demonstrable benefits. To offer the most informed recommendation, the clinician must have a strong working knowledge of the many drugs currently used as adjuvant analgesics and a detailed assessment of the patient and pain syndrome.

Dose-dependent competitive block by topical acetylsalicylic and salicylic acid of low pH-induced cutaneous pain

In a human acid pain model, which uses continuous intradermal pressure infusion of a phosphate-buffered solution (pH 5.2) to induce localized non-adapting pain, the flow was adjusted to result in constant pain ratings of about 20% or 50% on a visual analog scale (VAS). Six volunteers in each group participated in 4 different placebo-controlled double-blind cross-over studies to measure rapidly evolving cutaneous analgesia from topically applied new ointment formulations of acetylsalicylic acid (ASA) and salicylic acid (SA) as well as of commercial ibuprofen and benzocain creams. Similar, log-linear dose-response curves were found for both ASA and SA, significant in effect at 3 g/kg and higher drug contents and reaching saturation level at 15 or 30 g/kg, respectively, which, 20 min after application, caused a mean pain suppression of 95% using ASA and 80% using SA. Half-maximal effects were achieved using 3 g/kg ASA or 15 g/kg SA. The SA action was also clearly slower to develop. With an increased flow of the acidic buffer, producing lower effective tissue pH and more intense pain, the effect of ASA and SA decreased to 73% pain suppression. A competitive mechanism of both drug effects was suggested by the fact that, with 15 g/kg ASA and SA, pain reduction could be reversed by increasing the buffer flow by a factor of 1.75, on average. Commercial ibuprofen (50 g/kg) and benzocain creams (100 g/kg) were comparably as effective as ASA and SA, but the local anesthetic caused a loss of all cutaneous sensations while the touch threshold (von Frey) under the specific analgesics was the same as under the placebo ointment. Thus, topical applications of non-steroidal anti-inflammatory drugs (NSAIDS) dissolved in different ointment formulations have proven dose-dependently effective and specific in suppressing experimental acidotic pain by a local and competitive mechanism.

Topical acetylsalicylic, salicylic acid and indomethacin suppress pain from experimental tissue acidosis in human skin

Topically applied acetylsalicylic acid (ASA), salicylic acid (SA) and indomethacin were tested in an experimental pain model that provides direct nociceptor excitation through cutaneous tissue acidosis. In 30 volunteers, sustained burning pain was produced in the palmar forearm through a continuous intradermal pressure infusion of a phosphate-buffered isotonic solution (pH 5.2). In 5 different, double-blind, randomized cross-over studies with 6 volunteers each, the flow rate of the syringe pump was individually adjusted to result in constant pain ratings of around 20% (50% in study 4) on a visual analog scale (VAS). The painful skin area was then covered with either placebo or the drugs which had been dissolved in diethylether. In the first study on 6 volunteers, ASA (60 mg/ml) or lactose (placebo) in diethylether (10 ml) was applied, using both arms at 3-day intervals. Both treatments resulted in sudden and profound pain relief due to the cooling effect of the evaporating ether. With lactose, however, the mean pain rating was restored close to the baseline within 6-8 min while, with ASA, it remained significantly depressed for the rest of the observation period (another 20 min). This deep analgesia was not accompanied by a loss of tactile sensation. The further studies served to show that indomethacin (4.5 mg/ml) and SA (60 mg/ml) were equally effective as ASA (each 92-96% pain reduction) and that the antinociceptive effects were due to local but not systemic actions, since ASA and SA dis not reach measurable plasma levels up to 3 h after topical applications. With a higher flow rate of acid buffer producing more intense pain (VAS 50%). ASA and SA were still able to significantly reduce the ratings by 90% or 84%, respectively. On the other hand, by increasing the flow rate by a factor of 2 on average, during the period of fully developed drug effect it was possible to overcome the pain suppression, which suggests a competitive mechanism of (acetyl-) salicylic antinociception.

Topical lidocaine gel relieves postherpetic neuralgia

Postherpetic neuralgia (PHN) following herpes zoster is a common and disabling neuropathic pain syndrome. In a double-blind, three-session study, 5% lidocaine gel or vehicle was applied simultaneously to both the area of pain and to the contralateral mirror-image unaffected skin. In the local session, lidocaine gel was applied to the painful skin area. In the remote session, lidocaine gel was applied to mirror-image skin. In the placebo session, vehicle was applied bilaterally. For cranial PHN, gel was applied without occlusion for 8 hours. For limb or torso PHN, gel was applied under occlusion for 24 hours. The 16 subjects with cranial PHN reported pain relief significantly favoring local drug application at 30 minutes, 2, 4, and 8 hours. The 23 subjects with torso or limb PHN reported significantly lower pain intensity with local drug application at 8 hours and both pain relief and reduced pain intensity at 24 hours. Remote lidocaine application to mirror-image skin was no different from placebo. No systemic adverse effects were reported and blood levels did not exceed 0.6 microgram/ml. Topical application of 5% lidocaine gel relieves PHN pain by a direct drug action on painful skin.

Treatment of the cutaneous pain of acute herpes zoster with 9% lidocaine (base) in petrolatum/paraffin ointment

BACKGROUND

Treatment of the pain of acute herpes zoster by local anesthetic injections has drawbacks. Topical percutaneous local anesthesia (TPLA) may offer another strategy of providing regional analgesia in affected patients.

OBJECTIVE

We evaluate the analgesic efficacy and safety of 9% (wt/vol) lidocaine (base) in petrolatum/paraffin ointment in patients with acute herpes zoster.

METHODS

Ointment was applied to the affected skin of 22 patients. Pain, tenderness, sensitivity to pinprick and cold, and blood lidocaine concentration were measured repeatedly during a 20-hour interval and intermittently thereafter.

RESULTS

Mean pain, tenderness, and cutaneous sensation scores were reduced at measurements taken from 4 to 20 hours after ointment application (p < 0.05), but not every patient obtained relief. No patient had local skin irritation or systemic toxic effects related to the local anesthetic.

CONCLUSIONS

TPLA is a promising therapy for control of cutaneous pain of acute herpes zoster. Controlled studies should be performed to prove efficacy, determine optimal TPLA formulation, and define dosage limits.

Eutectic lidocaine/prilocaine cream. A review of the topical anaesthetic/analgesic efficacy of a eutectic mixture of local anaesthetics (EMLA)

Eutectic lidocaine/prilocaine cream 5% is a eutectic mixture of the local anaesthetics lidocaine (lignocaine) 25 mg/g and prilocaine 25 mg/g that provides dermal anaesthesia/analgesia following topical application. The principal indication in which eutectic lidocaine/prilocaine cream has been studied is the management of pain associated with venipuncture or intravenous cannulation, where significantly greater pain relief than placebo, with equivalent efficacy to ethyl chloride spray and lidocaine infiltration, has been demonstrated. In dermatological surgery, eutectic lidocaine/prilocaine cream offers effective pain relief in children undergoing curettage of molluscum contagiosum lesions, and in adults undergoing split-skin graft harvesting. Particular benefit has also been shown with use of eutectic lidocaine/prilocaine cream in association with treatment of condylomata acuminata in both men and women, and it appears to provide a useful alternative to lidocaine infiltration in this context. Further research in such indications as paediatric lumbar puncture, minor otological surgery, and minor gynaecological, urological and andrological procedures is likely to further broaden the profile of clinical use for eutectic lidocaine/prilocaine cream. Eutectic lidocaine/prilocaine cream has a very favourable tolerability profile, transient and mild skin blanching and erythema being the most frequent adverse events to occur in association with its application to skin. The potential for inducing methaemoglobinaemia, attributed to a metabolite of the prilocaine component of the formulation, prohibits its use in infants younger than 6 months. In summary, eutectic lidocaine/prilocaine cream is a novel formulation of local anaesthetics that has proven to be effective and well-tolerated in the relief of pain associated with various minor interventions in adults and children.

A new topical treatment for acute herpetic neuralgia and post-herpetic neuralgia: the aspirin/diethyl ether mixture. An open-label study plus a double-blind controlled clinical trial

Topical aspirin/diethyl ether (ADE) mixture was used to treat 45 consecutive patients with acute herpetic neuralgia (AHN) (n = 28) and with post-herpetic neuralgia (PHN) (n = 17) in an open-label study. Good-to-excellent results were achieved by 93% of AHN patients and by 65% of PHN patients. Earlier treatment yielded better results for the AHN but not the PHN group. The topical treatment seemed to accelerate the healing of acute herpetic skin lesions and possibly modulate the severity of the herpetic infection. Furthermore, a striking reduction in the percentage of AHN patients developing PHN was observed in the treated group, as compared with the disease natural history reported in the literature (4 vs. 50-70%). Treatment tolerance was excellent with no adverse effect observed. In addition to the open trial, a pilot double-blind crossover placebo-controlled study (n = 11) compared the analgesic efficacy of ADE with two other NSAID (indomethacin and diclofenac) drug/ether mixtures. Aspirin (but not indomethacin and diclofenac) was significantly superior to placebo as regards pain relief (P less than 0.05).