Painful peripheral diabetic neuropathy treated with venlafaxine HCl extended release capsules

Practical Management of Patients With Painful Diabetic Neuropathy

Purpose

Painful diabetic neuropathy (PDN) has a significant impact on patients’ quality of life, affecting sleep, mood, mobility, ability to work, interpersonal relationships, overall self-worth, and independence. The purpose of this article is to provide diabetes educators with current and essential tools for PDN assessment and management.

Methods

Medline and CINAHL database searches identified publications on the assessment and treatment of PDN. Identified research was evaluated, and information pertinent to diabetes educators was summarized.

Results

Recent advancements in assessment of neuropathic pain include identifying characteristics that distinguish between neuropathic and nonneuropathic pain. In the absence of treatment, research demonstrates that nerve damage may progress while pain diminishes. Many disease-modifying and symptom-management treatment options are available.

Conclusion

Good glycemic control is the first priority for both prevention and management of PDN. However, even with good glycemic control, up to 20% of patients will develop PDN. PDN recognition and assessment are critical to optimize management. Although several treatment modalities are available, few patients obtain complete pain relief. Recent advances in understanding the mechanisms underlying neuropathic pain should lead to better treatment and patient outcomes. Combination therapy, including nonpharmacologic modalities, may be required. Research evaluating the efficacy of combination therapy is needed.

Venlafaxine for neuropathic pain in adults

BACKGROUND

Neuropathic pain, which is caused by nerve damage, is increasing in prevalence worldwide. This may reflect improved diagnosis, or it may be due to increased incidence of diabetes-associated neuropathy, linked to increasing levels of obesity. Other types of neuropathic pain include post-herpetic neuralgia, trigeminal neuralgia, and neuralgia caused by chemotherapy. Antidepressant drugs are sometimes used to treat neuropathic pain; however, their analgesic efficacy is unclear. A previous Cochrane review that included all antidepressants for neuropathic pain is being replaced by new reviews of individual drugs examining chronic neuropathic pain in the first instance. Venlafaxine is a reasonably well-tolerated antidepressant and is a serotonin reuptake inhibitor and weak noradrenaline reuptake inhibitor. Although not licensed for the treatment of chronic or neuropathic pain in most countries, it is sometimes used for this indication.

OBJECTIVES

To assess the analgesic efficacy of, and the adverse effects associated with the clinical use of, venlafaxine for chronic neuropathic pain in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via The Cochrane Library, and MEDLINE and EMBASE via Ovid up to 14 August 2014. We reviewed the bibliographies of any randomised trials identified and review articles, contacted authors of one excluded study and searched www.clinicaltrials.gov to identify additional published or unpublished data. We also searched the meta-Register of controlled trials (mRCT) (www.controlled-trials.com/mrct) and the WHO International Clinical Trials Registry Platform (ICTRP) (apps.who.int/trialsearch/) for ongoing trials but did not find any relevant trials.

SELECTION CRITERIA

We included randomised, double-blind studies of at least two weeks' duration comparing venlafaxine with either placebo or another active treatment in chronic neuropathic pain in adults. All participants were aged 18 years or over and all included studies had at least 10 participants per treatment arm. We only included studies with full journal publication.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data using a standard form and assessed study quality. We intend to analyse data in three tiers of evidence as described by Hearn 2014, but did not find any first-tier evidence (ie evidence meeting current best standards, with minimal risk of bias) or second-tier evidence, that was considered at some risk of bias but with adequate participant numbers (at least 200 in the comparison). Third-tier evidence is that arising from studies with small numbers of participants; studies of short duration, studies that are likely to be of limited clinical utility due to other limitations, including selection bias and attrition bias; or a combination of these.

MAIN RESULTS

We found six randomised, double-blind trials of at least two weeks' duration eligible for inclusion. These trials included 460 participants with neuropathic pain, with most participants having painful diabetic neuropathy. Four studies were of cross-over design and two were parallel trials. Only one trial was both parallel design and placebo-controlled. Mean age of participants ranged from 48 to 59 years. In three studies (Forssell 2004, Jia 2006 and Tasmuth 2002), only mean data were reported. Comparators included placebo, imipramine, and carbamazepine and duration of treatment ranged from two to eight weeks. The risk of bias was considerable overall in the review, especially due to the small size of most studies and due to attrition bias. Four of the six studies reported some positive benefit for venlafaxine. In the largest study by Rowbotham, 2004, 56% of participants receiving venlafaxine 150 to 225 mg achieved at least a 50% reduction in pain intensity versus 34% of participants in the placebo group and the number needed to treat for an additional beneficial outcome was 4.5. However, this study was subject to significant selection bias. Known adverse effects of venlafaxine, including somnolence, dizziness, and mild gastrointestinal problems, were reported in all studies but were not particularly problematic and, overall, adverse effects were equally prominent in placebo or other active comparator groups.

AUTHORS' CONCLUSIONS

We found little compelling evidence to support the use of venlafaxine in neuropathic pain. While there was some third-tier evidence of benefit, this arose from studies that had methodological limitations and considerable risk of bias. Placebo effects were notably strong in several studies. Given that effective drug treatments for neuropathic pain are in current use, there is no evidence to revise prescribing guidelines to promote the use of venlafaxine in neuropathic pain. Although venlafaxine was generally reasonably well tolerated, there was some evidence that it can precipitate fatigue, somnolence, nausea, and dizziness in a minority of people.

A randomized controlled trial of venlafaxine XR for major depressive disorder after spinal cord injury: Methods and lessons learned

CONTEXT/OBJECTIVE

We describe the rationale, design, methods, and lessons learned conducting a treatment trial for major depressive disorder (MDD) or dysthymia in people with spinal cord injury (SCI).

DESIGN

A multi-site, double-blind, randomized (1:1) placebo controlled trial of venlafaxine XR for MDD or dysthymia. Subjects were block randomized and stratified by site, lifetime history of substance dependence, and prior history of MDD.

SETTING

Six SCI centers throughout the United States.

PARTICIPANTS

Across participating centers, 2536 subjects were screened and 133 were enrolled into the trial. Subjects were 18-64 years old and at least 1 month post-SCI. Interventions Twelve-week trial of venlafaxine XR versus placebo using a flexible titration schedule.

OUTCOME MEASURES

The primary outcome was improvement in depression severity at 12 weeks. The secondary outcome was improvement in pain.

RESULTS

This article includes study methods, modifications prompted by a formative review process, preliminary data on the study sample and lessons learned. We describe common methodological and operational challenges conducting multi-site trials and how we addressed them. Challenges included study organization and decision making, staff training, obtaining human subjects approval, standardization of measurement and treatment, data and safety monitoring, subject screening and recruitment, unblinding and continuity of care, database management, and data analysis.

CONCLUSIONS

The methodological and operational challenges we faced and the lessons we learned may provide useful information for researchers who aim to conduct clinical trials, especially in the area of medical treatment of depression in people with SCI.

Efficacy of venlafaxine for the prevention and relief of oxaliplatin-induced acute neurotoxicity: results of EFFOX, a randomized, double-blind, placebo-controlled phase III trial

BACKGROUND

Oxaliplatin neurosensory toxicity is dose limiting and may present as acute symptoms and/or cumulative peripheral neuropathy.

PATIENTS AND METHODS

From October 2005 to May 2008, patients with oxaliplatin-induced acute neurotoxicity were randomized into a double-blind study, to receive either venlafaxine 50 mg 1 h prior oxaliplatin infusion and venlafaxine extended release 37.5 mg b.i.d. from day 2 to day 11 or placebo. Neurotoxicity was evaluated using numeric rating scale (NRS) for pain intensity and experienced relief under treatment, the Neuropathic Pain Symptom Inventory and the oxaliplatin-specific neurotoxicity scale. The primary end point was the percentage of patients with a 100% relief under treatment.

RESULTS

Forty-eight patients were included (27 males, median age: 67.6 years). Most patients had colorectal cancer (72.9%). Median number of cycles administered at inclusion was 4.5 (mean cumulative oxaliplatin dose: 684.6 mg). Twenty out of 24 patients in arm A (venlafaxine) and 22 out of 24 patients in arm B (placebo) were assessable for neurotoxicity. Based on the NRS, full relief was more frequent in the venlafaxine arm: 31.3% versus 5.3% (P=0.03). Venlafaxine side-effects included grade 1-2 nausea (43.1%) and asthenia (39.2%) without grade 3-4 events.

CONCLUSION

Venlafaxine has clinical activity against oxaliplatin-induced acute neurosensory toxicity.

Peripheral Neuropathy Related to Chemotherapy

OBJECTIVES

To review the evidence base for prevention and intervention of chemotherapy-induced peripheral neuropathy (PN).

DATA SOURCES

Medical and nursing literature.

CONCLUSION

Many small studies that reported positive findings have either not been validated in large prospective, randomized controlled trials (RCT), or have not been further studied. Prevention strategies based on RCTs include the use of xaliproden to reduce the incidence of grade 3 PN in patients receiving oxaliplatin-based regimens, and dose reduction or interruption until recovery. There are gaps in the literature of nurse-sensitive outcome studies for nursing assessment and intervention

IMPLICATIONS FOR NURSING PRACTICE

Nurses need to be knowledgeable about the evidence, or lack of it, on strategies to prevent and manage chemotherapy-induced PN. Nurses also need to measure the effectiveness of interventions for PN, such as exercise, patient teaching about self-care strategies, and develop and/or participate in well-designed intervention studies regarding the prevention and management of PN.

Antidepressant pharmacotherapy: considerations for the pain clinician

Antidepressant pharmacotherapy presents many challenges to clinicians dealing with patients suffering from chronic pain. Co-existent depression and pain continues to present clinicians with a plethora of difficult treatment selections. Treated in isolation, each of these disease states can prove difficult to treat. Collectively, depression and pain often present significantly more difficult challenges to the clinician. Antidepressants may be used as a primary treatment modality for depression in a patient dealing with chronic pain. At other times these agents may be used to treat certain specific chronic pain syndromes, possibly in the face of concomitant depression. Clinicians should be aware of the many peculiarities associated with this broad class of medications. Included in this review are considerations for drug selection, dose escalation, and common drug related problems (eg, adverse drug reactions). In addition, attention is paid to the appropriate selection of an agent for use in either the primary management of pain or depression.

What is new in neuropathic pain?

INTRODUCTION

Neuropathic pain occurs in 1% of the population and is difficult to manage. Responses to single drugs are limited in benefit. Thirty percent will fail to respond altogether. This is a review of newer drugs and treatment paradigms.

METHODS

A literature review was performed pertinent to new drugs and treatment algorithms in the management of neuropathic pain.

RESULTS

New information on opioids (tramadol and buprenorphine) suggests benefits in the management of neuropathic pain and has increased interest in their use earlier in the course of illness. Newer antidepressants, selective noradrenaline, and serotonin reuptake inhibitors (SNRIs) have evidence for benefit and reduced toxicity without an economic disadvantage compared to tricyclic antidepressants (TCAs). Pregabalin and gabapentin are effective in diabetic neuropathy and postherpetic neuralgia. Treatment paradigms are shifting from sequential single drug trials to multiple drug therapies. Evidence is needed to justify this change in treatment approach.

CONCLUSION

Drug choices are now based not only on efficacy but also toxicity and drug interactions. For this reason, SNRIs and gabapentin/pregabalin have become popular though efficacy is not better than TCAs. Multiple drug therapies becoming an emergent treatment paradigm research in multiple drug therapy are needed.

Serotonin noradrenaline reuptake inhibitors: New hope for the treatment of chronic pain

Depression and painful symptoms occur frequently together. Over 75% of depressed patients report painful symptoms such as headache, stomach pain, neck and back pain as well as non-specific generalized pain. In addition, World Health Organization data have shown that primary care patients with chronic pain have a four fold greater risk of becoming depressed than pain-free patients. Increasingly, pain is considered as an integral symptom of depression and there evidence to suggest that pain and depression may arise from a common neurobiological dysfunction. Serotonergic cell bodies, in the raphe nucleus, and noradrenergic cell bodies in the locus coeruleus send projections to various parts of the brain, where they are involved in the control of mood, movement, cognitive functioning and emotions. In addition both serotonergic and noradrenergic neurons project to the spinal cord. These descending pathways serve to inhibit input from the intestines, skeletal muscles and other sensory inputs. Usually, these inhibitory effects are modest, but in times of stress, in the interest of the survival of the individual, they can completely inhibit the input from painful stimuli. A dysfunction of the serotonergic and noradrenergic neurons can thus affect both the ascending and descending pathways resulting in the psychological symptoms of depression and somatic pain symptoms such as chronic pain, fibromyalgia, non-cardiac chest pain, or irritable bowel syndrome. In view of this, it is not surprising that tricyclic antidepressants have been a standard treatment of chronic pain for many years. In contrast and in spite of their improved tolerance, selective serotonin reuptake inhibitors do not appear to be particularly effective in the treatment of pain. Recently, a number of open and controlled trials with selective serotonin and noradrenaline reuptake inhibitors such as venlafaxine, milnacipran and duloxetine, suggest that these compounds may be more effective in relieving pain than selective inhibitors of serotonin reuptake. Wherever valid comparisons have been made the newer dual action drugs appear to be as effective as the tricyclic and considerably better tolerated. Dual action antidepressants may thus soon become the new standard treatment of chronic pain whether it is associated with depression or not. In addition, these agents may also have a role in modulating neurogenesis and other neuroplastic changes in the central nervous system, thereby leading to more complete recovery in patients suffering from the symptoms of depression or chronic pain.

Pharmacologic management of neuropathic pain

The mechanisms underlying the pathogenesis of neuropathic pain are complex but are gradually coming to light. Agents that have been found effective in a variety of neuropathic pain conditions include drugs that act to modulate (a) sodium or calcium channels, (b) N-methyl-D-aspartate receptors, (c) norepinephrine or serotonin reuptake, (d) opioid receptors, and (e) other cellular processes. Clinical trials have primarily evaluated these treatments for postherpetic neuralgia and painful diabetic neuropathy, the two most common types of neuropathic pain. Nonetheless, the identification of effective treatment regimens remains challenging, often because multiple mechanisms may be operating in a given patient giving rise to the same symptom. Alternatively, a single mechanism may be responsible for multiple symptoms. Currently available diagnostic tools are inadequate to determine the best treatment using a mechanism-based model. Clinically, drug treatment of neuropathic pain is often a matter of treatment trials. This article presents a summary of available clinical information on first-line and lesser-known treatments for neuropathic pain.

Clinical experience with dual action antidepressants in different chronic pain syndromes

A common psychopharmacology between pain and depression suggests that compounds inhibiting the reuptake of serotonin and/or noradrenaline are likely to produce relief from chronic pain. Indeed tricyclic antidepressants have been a standard treatment of chronic pain for many years. In spite of their improved tolerance, selective serotonin reuptake inhibitors do not appear to be particularly effective in the treatment of pain. Recently, a number of open and controlled trials with members of the new selective serotonin and noradrenaline reuptake inhibitor class of antidepressants, such as venlafaxine, milnacipran and duloxetine, suggest that these compounds may be more effective in relieving pain than selective inhibitors of serotonin reuptake. Wherever valid comparisons have been made the newer dual action drugs appear to be as effective as the tricyclics and considerably better tolerated. Dual action antidepressants are thus likely to become a widely used treatment of chronic pain both associated with and independent of depression.

Efficacy of duloxetine, a potent and balanced serotonin-norepinephrine reuptake inhibitor in persistent pain models in rats

5-Hydroxytryptamine (serotonin) (5-HT) and norepinephrine (NE) are implicated in modulating descending inhibitory pain pathways in the central nervous system. Duloxetine is a selective and potent dual 5-HT and NE reuptake inhibitor (SNRI). The ability of duloxetine to antagonize 5-HT depletion in para-chloramphetamine-treated rats was comparable with that of paroxetine, a selective serotonin reuptake inhibitor (SSRI), whereas its ability to antagonize NE depletion in alpha-methyl-m-tyrosine-treated rats was similar to norepinephrine reuptake inhibitors (NRIs), thionisoxetine or desipramine. In this paradigm, duloxetine was also more potent than other SNRIs, including venlafaxine or milnacipran and amitriptyline. Low doses of the SSRI paroxetine or the NRI thionisoxetine alone did not have an effect on late phase paw-licking pain behavior in the formalin model of persistent pain; however, when combined, significantly attenuated this pain behavior. Duloxetine (3-15 mg/kg intraperitoneal) significantly attenuated late phase paw-licking behavior in a dose-dependent manner in the formalin model and was more potent than venlafaxine, milnacipran, and amitriptyline. These effects of duloxetine were evident at doses that did not cause neurologic deficits in the rotorod test. Duloxetine (5-30 mg/kg oral) was also more potent and efficacious than venlafaxine and milnacipran in reversing mechanical allodynia behavior in the L5/L6 spinal nerve ligation model of neuropathic pain. Duloxetine (3-30 mg/kg oral) was minimally efficacious in the tail-flick model of acute nociceptive pain. These data suggest that inhibition of both 5-HT and NE uptake may account for attenuation of persistent pain mechanisms. Thus, duloxetine may have utility in treatment of human persistent and neuropathic pain states.

Treatment of Pain Syndromes with Venlafaxine

Major depressive disorder (MDD) and anxiety disorders such as generalized anxiety disorder (GAD) are often accompanied by chronic painful symptoms. Examples of such symptoms are backache, headache, gastrointestinal pain, and joint pain. In addition, pain generally not associated with major depression or an anxiety disorder, such as peripheral neuropathic pain (e.g., diabetic neuropathy and postherpetic neuralgia), cancer pain, and fibromyalgia, can be challenging for primary care providers to treat. Antidepressants that block reuptake of both serotonin and norepinephrine, such as the tricyclic antidepressants (e.g., amitriptyline), have been used to treat pain syndromes in patients with or without comorbid MDD or GAD. Venlafaxine, a serotonin and norepinephrine reuptake inhibitor, has been safe and effective in animal models, healthy human volunteers, and patients for treatment of various pain syndromes. The use of venlafaxine for treatment of pain associated with MDD or GAD, neuropathic pain, headache, fibromyalgia, and postmastectomy pain syndrome is reviewed. Currently, no antidepressants, including venlafaxine, are approved for the treatment of chronic pain syndromes. Additional randomized, controlled trials are necessary to fully elucidate the role of venlafaxine in the treatment of chronic pain.

Evaluation of efficacy of the perioperative administration of venlafaxine XR in the prevention of postmastectomy pain syndrome

Postmastectomy pain syndrome (PMPS) is a neuropathic pain syndrome that may develop following breast surgery. Venlafaxine has been shown to be efficacious in the management of PMPS. The preemptive administration of venlafaxine has been shown to be efficacious in reducing the incidence of neuropathic pain in the rat model. We examined the efficacy of administering either venlafaxine or placebo for two weeks starting the night before surgery to 100 patients scheduled for either partial or radical mastectomy with axillary dissection. Patients were administered PCA morphine for the first 24 hours following surgery and then acetaminophen/oxycodone tablets. Pain scores were recorded at rest and movement on day 1, at 1 month, and at 6 months after surgery. At 6 months postoperatively, the presence of pain in the chest, arm, and axilla; edema; decreased sensation in the operative area; and phantom breast pain were recorded. There was no difference in postoperative opioid use. Pain scores with movement were lower in the venlafaxine group at 6 months. Pain scores at all other time intervals were similar. There was a significant decrease in the incidence of chest wall pain (55% vs. 19%, P = 0.0002), arm pain (45% vs. 17%, P = 0.003), and axilla pain (51% vs. 19%, P = 0.0009) between the control group and the venlafaxine group, respectively. No significant differences were noted between the two groups with regard to edema, phantom pain, or sensory changes. We conclude that the perioperative administration of venlafaxine beginning the night prior to surgery significantly reduces the incidence of PMPS following breast cancer surgery.

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.

Medical evaluation and treatment of diabetic peripheral neuropathy

Diabetes mellitus is a major health concern that is only expected to become more prevalent over the next few decades. It causes much morbidity and mortality through various macro- and microvascular complications, including diabetic neuropathy. Currently, there is no treatment that directly affects the natural course of diabetic neuropathy except for rigorous glycemic control, a goal that is not always achievable. Despite these therapeutic limitations, the morbidity caused by diabetic neuropathy can be minimized by early and accurate diagnosis. A detailed history and physical examination, along with carefully selected laboratory tests will confirm the presence of diabetic neuropathy while excluding other etiologies that may require alternative management strategies. Treatment is always tailored to the patient's symptoms. In addition to improved glycemic control, health care providers can provide education, support, and symptomatic relief. There are many pain modulating therapies that are effective in diabetic neuropathy as discussed above. Nortriptyline at low doses is an inexpensive well-tolerated medication that is effective. Gabapentin is an excellent choice when nortriptyline is ineffective or not tolerated. Other anticonvulsants, such as lamotrigine, carbamazepine, oxycarbazepine, and topiramate, may also provide benefit. Judicious use of narcotics is appropriate when other treatment modalities fail. The importance of treating underlying depression cannot be overemphasized. When gait becomes impaired as a result of neuropathy, appropriate prescription of assistive devices will prevent injuries from falls. Ankle-foot orthoses and other orthotic devices may allow patients to remain ambulatory and independent for a longer period. Despite the challenges ahead, the future holds the promise of more effective treatments for diabetes mellitus and its complications.

Efficacy of venlafaxine for the long term treatment of chronic pain with associated major depressive disorder

BACKGROUND

This was an open-label, single-center study of the long-term efficacy and effectiveness of venlafaxine extended release (XR) in the treatment of chronic pain and depression in outpatients. All patients have been diagnosed with major depressive disorder (MDD) of various types, with or without chronic pain, and had previously failed treatment with either tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs).

METHODS

Efficacy of treatment was determined using the 21-item Hamilton Rating Scale for Depression (HAMD-21), the Visual Analogue Scale (VAS) for the evaluation of pain, and a 12-item quality of life scale (QOL). Patients were treated in an unblended open trial for 1 year with 150 mg or more of venlafaxine XR once daily.

RESULTS

After 1 year of treatment, 21-item Hamilton Rating Scale for Depression, Visual Analogue Scale, and quality of life scores were significantly improved from permanent baseline scores.

CONCLUSION

These data show long-term efficacy and effectiveness of venlafaxine XR, a serotonin (5-HT) and norepinephrine (NE) and dopamine (DA) reuptake inhibitor antidepressant agent, having analgesic properties.

Protection against oxaliplatin acute neurosensory toxicity by venlafaxine

Venlafaxine (Effexor; Wyeth Lederlé) has previously shown therapeutic effects for the management of chronic and neuropathic pains. We report here the efficacy of venlafaxine upon acute neurosensory symptoms secondary to oxaliplatin toxicity. A dose of 50 mg of venlafaxine was given orally at the beginning of the oxaliplatin infusion. Patients did not experience any or very low paresthesias, even in the cold. As the results were very dramatic and reproducible, we propose that venlafaxine may be of use in the daily management of oxaliplatin-related neurosensory toxicity.

Pharmacotherapy of painful diabetic neuropathy

The scope of this review is to describe the epidemiology, physiology, symptomatology, and treatment of diabetic painful neuropathy, which is a common complication of diabetes with significant morbidity. This article focuses on treatment options. Various clinical trials of several classes of medications (eg, antidepressants, anticonvulsants, and topical medications) and alternative treatments (eg, acupuncture, electrostimulation, magnets) are reviewed. Physicians have a large panel of medications that can be used effectively solely or in combination at their disposal. However, a number of these treatments have significant side effects, which are noted, that limit their use. As the understanding of the pathophysiologic mechanisms of diabetic neuropathy improves, new medications are under investigation, which are reviewed in this article. There is great hope that the future may hold treatments that would prevent nerve damage.

The antihyperalgesic effect of venlafaxine in diabetic rats does not involve the opioid system

Venlafaxine (VFX) is a structurally novel antidepressant that inhibits reuptake of serotonin and norepinephrine but, unlike tricyclic antidepressants, has few side effects. The present work studies the antihyperalgesic effect of repeated administrations of VFX (five successive injections of 2.5, 5 or 10 mg/kg, s.c., every half-life) in diabetic rats with the paw pressure test and the effect of the opioid receptor antagonist naloxone (1 mg/kg, i.v.) because an opioidergic mechanism is usually considered to be involved in the analgesic effect of antidepressants. VFX induced a significant dose-dependent increase in vocalization thresholds. This effect was not reversed by naloxone. Thus, we demonstrate a clear antinociceptive effect of VFX which, unlike that of most mixed tricyclic antidepressants, does not involve the endogenous opioid system.

Current and Future Strategies for the Management of Diabetic Neuropathy

Diabetic neuropathy is common, related to increased morbidity and mortality, and has no effective treatment at present. Interventions based on putative pathways thought to contribute to damage and repair of nerve fibres have yielded little success to date. Pain is a potentially debilitating manifestation of diabetic neuropathy and has many potential sites of origin and, hence, modulation. Its cause is unclear and it does not respond well to traditional pain therapies, proposed to mediate their benefits via multiple peripheral and central mechanisms. A better understanding of the mechanisms leading to nerve fibre degeneration and regeneration as well as pain has recently resulted in the development of a more targeted approach to the treatment of diabetic neuropathy. Thus, specific NMDA receptor antagonists and more specific neuronal serotonin and norepinephrine (noradrenaline) uptake inhibitors offer promise in the treatment of painful diabetic neuropathy. A number of treatments which include the aldose reductase inhibitors and neurotrophins have failed to reach the clinical arena. However, the antioxidant alpha-lipoic acid, as well as compounds which correct vascular dysfunction and hence neuropathy, such as ACE inhibitors and protein kinase C-beta inhibitors, have demonstrated more success.

Dramatic recovery of paclitaxel-disabling neurosensory toxicity following treatment with venlafaxine

Venlafaxine is an antidepressant which acts through the inhibition of the reuptake of norepinephrine and serotonin. Venlafaxine is active against neuropathic and chronic pain. We report the case of a 69-year-old woman who presented a paclitaxel-induced neuropathy. She presented paresthesias, pin pricks in both hands with functional impairment. Venlafaxine hydrochloride was introduced at 37.5 mg twice daily. The patient noticed a dramatic recovery of her symptoms within 2 days, with both reduction of the paresthesias and functional improvement. This is the first report of efficacious use of venlafaxine for the treatment of paclitaxel cumulative neurosensory toxicity.

Recent advances in pharmacotherapy for cancer pain management

PURPOSE

This review provides an outline of several recent advances in drug treatment options and strategies for managing cancer pain.

OVERVIEW

The development of cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) and transmucosal fentanyl citrate provide new pharmacologic options for the treatment of cancer pain. Combinations of opioid agonists and antagonists have provided data on new strategies to balance effective analgesia with analgesic-related adverse effects. In addition, the spectrum of adjuvant agents for the treatment of neuropathic pain has been extended to various antidepressants and topical analgesics. There is continued research on the role of the N-methyl-d-aspartate (NMDA) receptor and, specifically, on NMDA receptor antagonists that may augment analgesia and combat opioid resistance. Finally, a more potent generation of bisphosphonates may lead to improved pain relief for patients with bone metastases.

CLINICAL IMPLICATIONS

With a combination of emerging new clinical research and professional practice experience of the cancer care team, new strategies will continue to be developed and implemented, resulting in the continued improved care of patients with cancer.

Venlafaxine in neuropathic pain following treatment of breast cancer

Amitriptyline effectively relieves neuropathic pain following treatment of breast cancer. However, adverse effects are a major problem. Venlafaxine has no anticholinergic effects and could have a better compliance. The aim of the study was to evaluate the effectiveness of venlafaxine in neuropathic pain. The study was a randomized, double-blind, crossover comparison of venlafaxine and inactive placebo. The study lasted 10 weeks. The number of tablets (18.75 mg) taken daily was increased by one at a 1 week interval. Pain intensity and pain relief were registered daily by a diary and by a questionnaire and a computer program (Painscreen) on each visit. Adverse effects were evaluated with the diaries and a 10-item list on each visit. Also, anxiety and depression were measured on each visit. Venous blood samples were collected before the treatment and at 4 weeks for the determination of the serum levels of venlafaxine and its three metabolites. Thirteen patients were analysed. The average daily pain intensity as reported in the diary (primary outcome) was not significantly reduced by venlafaxine compared with placebo. However, the average pain relief (diary) and the maximum pain intensity (retrospective assessment by the computer program) were significantly lower with venlafaxine compared with placebo. Anxiety and depression were not affected. Adverse effects did not show significant differences between treatments. The two poor responders had low venlafaxine concentrations whereas the two slow hydroxylizers had high venlafaxine concentrations and excellent pain relief. Thus, higher doses could be used in order to improve pain relief.

The psychopharmacologic treatment of depression and anxiety in the context of chronic pain

Chronic pain afflicts millions of people, commonly causing depression and anxiety. These conditions must be treated to achieve a good functional outcome from pain treatment. Selective serotonin reuptake inhibitors, tricyclics, and newer antidepressants effectively treat both depression and selected anxiety disorders. Antidepressants with noradrenergic and serotinergic activity, and anticonvulsants, which may also stabilize mood, are effective in neuropathic pain. Other medications have limited but important pharmacotherapeutic roles.

Management of painful diabetic neuropathy

Type 2 diabetes mellitus is a prevalent disease in the US which affects more than 15 million people. As the disease progresses over time, neuropathic pain can become a common complication; it is present in more than 50% of individuals with diabetes mellitus aged >60 years. The pathogenesis of diabetic neuropathy is theorized to be multifactorial. Numerous medications, some with different mechanisms of action, have been examined regarding their effects on the symptoms associated with diabetic neuropathy such as pain, paraesthesia and numbness. However, the majority of the studies have included small patient populations. Tricyclic antidepressants, amitriptyline and desipramine in particular, have been relatively well studied and shown to be effective. However, anticholinergic adverse effects may limit their usefulness and may preclude use in the elderly. Studies have also shown gabapentin to be effective and well tolerated in the treatment of diabetic neuropathy. Capsaicin cream provides another treatment option with a favourable adverse effect profile. Many other medications have been evaluated in diabetic neuropathy; however, more placebo-controlled studies with adequate patient populations need to be performed to solidify their role in treatment.

Treatments for diabetic neuropathy

The management of symptomatic diabetic sensory neuropathy presents a therapeutic challenge to the practicing physician. Two approaches are outlined in this article. First, symptomatic therapies, which will not influence the natural history of painful neuropathy, are discussed. These include, in addition to the stable glycemic control, tricyclic drugs, a number of anticonvulsant and antiarrhythmic agents, and opioid-like medications. Topical therapies and nonpharmalogic approaches are also discussed. With the exception of near normoglycemia, treatments that may slow the progression of neuropathy are experimental and include aldose reductase inhibitors, antioxidants, and other agents. Finally, the approach to patients without symptoms but with sensory loss is discussed.

Efficacy of venlafaxine in geriatric depression

Geriatric patients with major depression present clinical challenges not encountered in younger individuals, including a greater incidence of medical comorbidity, higher rates of multiple medication use, changes in drug metabolism due to age or physical illness, and increased sensitivity to antidepressant side effects. Nevertheless, successful treatment of depressive disorders in the elderly improves mental and physical functioning, decreases morbidity and perhaps mortality, and enhances quality of life. Recent research indicates that newer antidepressants are effective for late life depression and safer for older individuals. Among newer antidepressants, venlafaxine has a pharmacological profile that makes it an attractive choice for geriatric patients. It has limited potential to interact with other medications because it only weakly inhibits the cytochrome P450 system and binds to plasma proteins at a low level. Dosing may have to be adjusted for patients with renal failure, but typically not for those with liver disease or other medical conditions. Data from three double-blind and four open clinical trials support the safety and efficacy of venlafaxine for geriatric depression. Patients may experience transient, generally tolerable side effects such as insomnia, nausea, agitation, or dry mouth early in treatment, but more serious problems such as falls or cardiac rhythm disturbances seem to be rare. Treatment emergent hypertension occurs in a small percentage of older patients, generally at doses above 150 mg/day. Finally, emerging data suggest that venlafaxine may be effective for conditions such as stroke, anxiety, and neuropathic pain that frequently accompany depressive disorders in the elderly.

Neuropharmacology of venlafaxine

Venlafaxine (Effexor) is an effective antidepressant and has also been approved for the treatment of generalized anxiety disorder. Venlafaxine was initially characterized as an inhibitor of both serotonin (5HT) and norepinephrine (NE) uptake and was therefore termed a "dual uptake inhibitor." This chapter reviews data from both in vitro and in vivo studies regarding its effects on 5HT and NE neurotransmission. In addition, the effects of venlafaxine on other systems that may play a role in its therapeutic efficacy effects are described. The data indicate that venlafaxine is a relatively weak inhibitor of NE transport in vitro. In vivo studies indicate that venlafaxine selectively inhibits 5HT uptake at low therapeutic doses and inhibits both 5HT and NE uptake at higher therapeutic doses. This chapter concludes with a discussion of the effects of venlafaxine on various aspects of physiology.

Status of current clinical trials in diabetic polyneuropathy

Peripheral polyneuropathy is the most frequent complication of diabetic mellitus. In spite of many clinical trials of different specific interventions for diabetic polyneuropathy, intensive glycemic control remains the only effective specific therapy currently available for this troublesome complication. This systematic overview reports the status of current clinical trials in diabetic polyneuropathy with an emphasis on those interventions directed towards specific pathophysiological derangements. A discussion of clinical trials of agents directed towards relieving painful symptoms of diabetic polyneuropathy concludes this overview.

Treatment of neuropathic pain with venlafaxine

OBJECTIVE

To report a case of successful treatment of neuropathic pain with venlafaxine.

CASE REPORT

A 39-year-old white woman presented with neuropathic back pain. The patient obtained 50% pain relief with consecutive use of amitriptyline, desipramine, and imipramine. Anticholinergic effects prompted a switch to extended-release venlafaxine 75 mg/d. Pain relief was as effective with this therapy as with the tricyclic antidepressants. The absence of adverse effects allowed the patient to discontinue all laxatives.

DISCUSSION

Venlafaxine is an antidepressant that inhibits reuptake of norepinephrine and serotonin. This is the major mechanism by which tricyclic antidepressants relieve neuropathic pain. Venlafaxine does not bind to muscarinic-cholinergic, histaminic or alpha1-adrenergic receptors responsible for the common adverse effects seen with tricyclic antidepressants.

CONCLUSIONS

This report describes the efficacious use of venlafaxine in the treatment of neuropathic pain. Double-blind, randomized, controlled trials are needed to explore this further.