Venlafaxine for the treatment of neuropathic pain

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contacted authors of one excluded study and searched www.clinicaltrials.gov to identify additional published or unpublished data.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.

Undiagnosed mood disorders and sleep disturbances in primary care patients with chronic musculoskeletal pain

OBJECTIVE

The study aims to determine the prevalence of undiagnosed comorbid mood disorders in patients suffering chronic musculoskeletal pain in a primary care setting and to identify sleep disturbances and other associated factors in these patients, and to compare the use of health services by chronic musculoskeletal pain patients with and without comorbid mood disorders.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 1,006 patients with chronic musculoskeletal pain from a representative sample of primary care centers were evaluated.

OUTCOME MEASURES

Pain was measured using a visual analog scale and the Primary Care Evaluation of Mental Disorders questionnaire was used to measure mood disorders.

RESULTS

We observed a high prevalence of undiagnosed mood disorders in chronic musculoskeletal pain patients (74.7%, 95% confidence interval [CI] 71.9-77.4%), with greater comorbidity in women (adjusted odds ratio [OR] = 1.91, 95% CI 1.37-2.66%) and widow(er)s (adjusted OR = 1.87, 95% CI 1.19-2.91%). Both sleep disturbances (adjusted OR = 1.60, 95% CI 1.17-2.19%) and pain intensity (adjusted OR = 1.02, 95% CI 1.01-1.02%) displayed a direct relationship with mood disorders. Moreover, we found that chronic musculoskeletal pain patients with comorbid mood disorders availed of health care services more frequently than those without (P < 0.001).

CONCLUSIONS

The prevalence of undiagnosed mood disorders in patients with chronic musculoskeletal pain is very high in primary care settings. Our findings suggest that greater attention should be paid to this condition in general practice and that sleep disorders should be evaluated in greater detail to achieve accurate diagnoses and select the most appropriate treatment.

Factors associated with chronic pain in patients with bipolar depression: a cross-sectional study

BACKGROUND

While pain is frequently associated with unipolar depression, few studies have investigated the link between pain and bipolar depression. In the present study we estimated the prevalence and characteristics of pain among patients with bipolar depression treated by psychiatrists in their regular clinical practice. The study was designed to identify factors associated with the manifestation of pain in these patients.

METHODS

Patients diagnosed with bipolar disorder (n=121) were selected to participate in a cross-sectional study in which DSM-IV-TR criteria were employed to identify depressive episodes. The patients were asked to describe any pain experienced during the study, and in the 6 weeks beforehand, by means of a Visual Analogical Scale (VAS).

RESULTS

Over half of the bipolar depressed patients (51.2%, 95% CI: 41.9%-60.6%), and 2/3 of the female experienced concomitant pain. The pain was of moderate to severe intensity and prolonged duration, and it occurred at multiple sites, significantly limiting the patient's everyday activities. The most important factors associated with the presence of pain were older age, sleep disorders and delayed diagnosis of bipolar disorder.

CONCLUSIONS

Chronic pain is common in bipolar depressed patients, and it is related to sleep disorders and delayed diagnosis of their disorder. More attention should be paid to study the presence of pain in bipolar depressed patients, in order to achieve more accurate diagnoses and to provide better treatment options.

Evaluation of efficacy of the perioperative administration of Venlafaxine or gabapentin on acute and chronic postmastectomy pain

OBJECTIVES

Postmastectomy pain syndrome is a neuropathic pain syndrome that is known to develop after breast surgery. Preemptive analgesia has been shown to be efficacious in reducing postoperative pain, and may be effective in reducing the incidence of certain types of neuropathic pain. We investigated the analgesic efficacy of Venlafaxine and gabapentin on acute and chronic pain associated with cancer breast surgery.

PATIENTS AND METHODS

The study was carried out on 150 patients scheduled for either partial or radical mastectomy with axillary dissection. They were randomized in a double-blinded manner to receive, extended release Venlafaxine 37.5 mg/d, gabapentin 300 mg/d, or placebo for 10 days starting the night before operation. Pain scores were recorded at rest and movement (visual analog scale) at 4, 12, and 24 hours on the first day postoperatively, daily from the second to tenth day postoperatively and visual analog scale in addition to pain character 6 months later. Analgesic requirements were compared between the 3 groups.

RESULTS

Pain after movement was reduced by gabapentin from the second to tenth postoperative day and venlafaxine group in the last 3 days but no difference was found between the groups regarding pain during rest. Gabapentin reduced morphine consumed in the first 24 hours postoperatively. The analgesic requirements from the second to tenth days for codeine and paracetamol were reduced in venlafaxine and gabapentin groups compared to the control group. Six months later, the incidence of chronic pain, its intensity, and need for analgesics were reduced in venlafaxine compared to gabapentin and the placebo group. However, burning pain was more frequent in the control groups than in the gabapentin.

CONCLUSION

Venlafaxine 37.5 mg/d extended release or gabapentin 300 mg/d have equipotent effects (except on the first day in venlafaxine group) in reducing analgesic requirements, although gabapentin is more effective in reducing pain after movement. Venlafaxine significantly reduced the incidence of postmastectomy pain syndromes (chronic pain) 6 months in women having breast cancer surgery. Gabapentin had no effect on chronic pain except decreasing incidence of burning pain.

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.

The Coexistence of Neuropathic Pain, Sleep, and Psychiatric Disorders

The diagnosis and treatment of neuropathic pain may be complicated by comorbid conditions such as sleep disturbances, depression, and anxiety. The interrelationship between the index neuropathic pain state and these comorbidities is complex: comorbid conditions exacerbate pain, and in turn, pain exacerbates the comorbid conditions. Because comorbidities can negatively impact response to pain treatment, healthcare providers should assess comorbidities as part of the diagnostic work-up, and management strategies should be designed to treat the whole patient, not just the pain. Theoretically, therapies that not only reduce pain, but also improve sleep and reduce anxiety and depression can provide multiple benefits without the risk of increased side effects inherent in combination therapy. Anticonvulsants and antidepressants have demonstrated efficacy in improving neuropathic pain and positively impacting comorbid sleep and mood disturbances. Novel anticonvulsants that can address one or more comorbidities in addition to pain may represent viable treatment options for patients with neuropathic pain.

Arzneimitteltherapie des Reizdarmsyndroms

The therapy of patients with irritable bowel syndrome (IBS) is often challenging, especially if a broad spectrum of symptoms is present and trigger factors, such as the influence of diet or stress, are lacking. Current pathogenetic concepts propose central or peripheral alterations that cause disturbed gastrointestinal function (motility, visceral sensitivity) and subsequent symptoms. These alterations are possibly related to psychological (stress, depression, anxiety) and biological (post-infectious residuals, micro-inflammation) influences. Since no universally effective medical treatment is available to treat the causes of the disease, standard medical therapy is symptom directed (especially for pain, constipation and diarrhoea). In addition to well established drugs (like spasmolytics, opioids and laxatives), newly developed compounds including those with other primarily indications (e.g. antidepressants) are available for highly differentiated individualized therapies. New medical approaches which are currently undergoing evaluation, promise further progress in the treatment of IBS.

Emerging therapies for neuropathic pain

Neuropathic pain develops as a result of damage to either the peripheral or central nervous system. It is characterised by spontaneous burning pain and/or ongoing pain with accompanying hyperalgesia and allodynia. Neuropathic pain is difficult to treat as it is often refractory to conventional analgesic treatments, with most patients obtaining only partial relief. At present, there are four major medication categories that are considered first-line treatment for neuropathic pain: antidepressants, anticonvulsants, local anaesthetic/topical agents and opioids. The efficacy of these treatments in neuropathic pain, excepting opioids, has been discovered serendipitously. However, responder rates and overall efficacy is poor with these agents and tolerability or side effects are often limiting. This update will review existing treatment options for neuropathic pain, and highlight more recent advances in the development of novel analgesics to treat this chronic disorder.

Psychosocial assessment of functional gastrointestinal disorders in clinical practice

Functional gastrointestinal disorders are the most common conditions encountered in gastroenterology practice and are also commonly encountered in primary care. Psychosocial factors play an important role in these disorders (along with any chronic digestive disorder) by influencing healthcare seeking, illness behavior, symptom severity, quality of life, and digestive motility and sensation. Identification of relevant psychosocial factors in patients with chronic digestive disorders influences care and is a critical determinant of outcomes. This article provides a review of relevant psychosocial variables, assessment techniques, and therapeutic suggestions that can be of value in assessing patients with functional gastrointestinal disorders.

Effect of the antidepressant nefazodone on the density of cells expressing mu-opioid receptors in discrete brain areas processing sensory and affective dimensions of pain

RATIONALE

The principal use of antidepressants is in the treatment of depression and affective disorders. Antidepressants have also been used as an adjuvant to analgesics in pain treatment. However, in chronic treatment, their antinociceptive and antidepressive effects coexist simultaneously. Antidepressants can interact with the opioid system, which is also involved in regulating nociceptive processing and affective state. Chronic antidepressants could act by increasing mu-opioid receptor expression in many brain areas involved in the regulation of nociception and affective state.

OBJECTIVES

The aim of this study was to evaluate the antinociceptive and antidepressant-like effects and the possible variations in mu-opioid receptor expression induced by a chronic nefazodone treatment in brain areas related to pain and affective state.

METHODS

Wistar rats were chronically treated with nefazodone (10 and 25 mg/kg IP, twice a day, for 14 days). Twelve hours after the last day 14 dose of nefazodone, a tail-flick test was performed. After the administration of a daily dose of nefazodone, Porsolt's test was carried out 12 h after last dose. Two hours after completion of 14 days treatment, other animals were processed for mu-opioid receptor immunocytochemistry using polyclonal antisera raised in rabbits. Several brain regions were analyzed: the frontal and cingulate cortex, the dorsal raphe nucleus and the periaqueductal gray.

RESULTS

Chronic nefazodone treatment induced a significant increase in tail-flick latency and a significant decrease in immobility time at total doses of 20 and 50 mg/kg per day ( P<0.05). In treated animals, the density of neural cells immunostained for mu-opioid receptor in the frontal and cingulate cortices, dorsal raphe nucleus and periaqueductal gray had increased after chronic nefazodone compared to controls.

CONCLUSION

Therefore, chronic nefazodone induces antinociceptive and antidepressant-like effects in rats and increases mu-opioid receptor expression in brain areas related to pain and affective state. These results suggest that antidepressants could be effective on somatic and affective dimensions of pain and this action could be related to its influence on the opioid system.

Antidepressant-like effect of tramadol and its enantiomers in reserpinized mice: comparative study with desipramine, fluvoxamine, venlafaxine and opiates

Tramadol is a centrally acting analgesic that demonstrates opioid and monoaminergic properties. Several studies have suggested that tramadol could play a role in mood improvement. Moreover, it has previously been shown that tramadol is effective in the forced swimming test in mice and the learned helplessness model in rats, two behavioural models predictive of antidepressant activity. The aim of the present study was to test tramadol and its enantiomers in the reserpine test in mice, a classical observational test widely used in the screening of antidepressant drugs. This test is a non-behavioural method where only objective parameters such as rectal temperature and palprebral ptosis are considered. Moreover, we compared the effects of tramadol and its enantiomers with those of antidepressants (desipramine, fluvoxamine and venlafaxine) and opiates [morphine (-)-methadone and levorphanol]. Racemic tramadol, (-)-tramadol, desipramine and venlafaxine reversed the reserpine syndrome (rectal temperature and ptosis), whereas(+)-tramadol and fluvoxamine only antagonized the reserpine-induced ptosis, without any effect on temperature. Opiates did not reverse reserpine-induced hypothermia. (-)-Methadone showed slight effects regarding reserpine-induced ptosis, morphine and levorphanol had no effect. These results show that tramadol has an effect comparable to clinically effective antidepressants in a test predictive of antidepressant activity, without behavioural implications. Together with other clinical and experimental data, this suggests that tramadol has an inherent antidepressant-like (mood improving) activity, and that this effect could have clinical repercussions on the affective component of pain.

Non-selective opioid receptor antagonism of the antidepressant-like effect of venlafaxine in the forced swimming test in mice

The opioid system has been implicated in mood disorders as well as in the mechanism of action of antidepressants. Since the opioid component in venlafaxine (VLX) is still a matter of discussion, we investigated the role of opioid receptors in the antidepressant-like effect of VLX in the forced swimming test in mice. The non-selective opiate antagonist naloxone at high dose (2 mg/kg, s.c.) antagonized the effect of VLX. In contrast, beta-funaltrexamine (40 mg/kg, s.c.), which preferentially blocks mu(1)/mu(2) opioid receptors, naloxonazine (35 mg/kg, s.c.), a selective mu(1) opioid antagonist, naltrindole (10 mg/kg, s.c.), a selective delta opioid antagonist, and Nor-binaltorphimine (10 mg/kg, s.c.), which selectively blocks kappa-opioid receptors, were all ineffective. Thus, although apparently mediated by the opioid system, the behavioural effect of VLX does not involve specific opioid receptors.

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.

Cancer pain and depression: management of the dual-diagnosed patient

Depressive disorders and pain syndromes are very common in the experience of cancer patients and may be experienced simultaneously. There is an intuitive association between cancer pain and cancer depression, both of which are multidimensional entities. Research has suggested, but not conclusively proven a cause-effect relationship. Suicidal ideation is a common concern in cancer patients with severe depression or pain. Antidepressant therapy is a mainstay of management of depression. That some antidepressants have use in the management of cancer pain may influence choice of drug selection in depressed patients. Antidepressant side effects and the patient's drug history are relevant variables. Because antidepressants that are effective as coanalgesics may not be tolerated at doses effective for depression, the clinician must be familiar with newer classes of antidepressants and psychostimulants. Combination drug therapy may be required. Psychotherapy also is common to the treatment of cancer pain and depression. With or without the intervention of pain and mental health specialists, ongoing supportive therapy from the primary clinician is essential.

Antidepressant-like effects of tramadol and other central analgesics with activity on monoamines reuptake, in helpless rats

Affective states are regulated mainly by serotonin and noradrenaline. However the opioid system has been also related to antidepressant-induced mood improvement, and the mu-opioid receptor has been involved in affective responses to a sustained painful stimulus. Similarly, antidepressant drugs induce an antinociceptive effect via both the monoaminergic and opioid systems, probably involving sensorial and affective dimensions of pain. The aim of this study was to test three opiate analgesics, which also inhibit monoamine reuptake, in the learned helplessness model of depression in rats. Helpless rats receiving (+/-)tramadol (10, 20 mg/Kg) or (-)methadone (2, 4 mg/Kg) showed a decreased number of failures to avoid or escape aversive stimulus (shock) in both the second and the third daily sessions, compared with controls. Rats receiving levorphanol (0.5, 1 mg/Kg) showed a decreased number of such failures in the third session. The number of crossings in the intertrial interval (ITI) was not significantly modified by (+/-)tramadol or (-)methadone. Levorphanol enhanced ITI crosses at 1 mg/Kg. These results, together with other clinical and experimental data, suggest that analgesics with monoaminergic properties improve mood and that this effect may account for their analgesic effect in regulating the affective dimension of pain. From this, it seems probable that the analgesic effect of opiates could be induced by adding together the attenuation produced of both the sensorial and the affective dimensions of pain.

Evidence review: efficacy and effectiveness of antidepressant treatment in primary care

This review considers evidence for the efficacy of pharmacotherapy among primary care patients with depressive disorders and reviews knowledge regarding the effectiveness of current practice. Strong evidence supports the efficacy of antidepressant pharmacotherapy for primary care patients with major depression and dysthymia with some evidence for pharmacotherapy of less severe depression. In general, available antidepressants appear equal in both efficacy and effectiveness. Treatment selection for any individual patient remains largely empirical, with few clinical characteristics predicting better or worse response to specific treatments. Strong evidence supports continuation treatment (i.e., at least six months of pharmacotherapy) for all patients and maintenance treatment (i.e., at least 24 months of pharmacotherapy) for those with chronic or recurrent depression. Unfortunately, few patients in primary care or specialty practice receive recommended levels of pharmacotherapy or recommended frequency of follow-up care. A number of recent studies have evaluated strategies to improve the quality of antidepressant treatment in primary care. Educational programs (including academic detailing and continuous quality improvement) have had little impact on patient outcomes. Key elements of effective care improvement programs include specific, evidence-based treatment protocols, organized patient education and active follow-up care.

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.

Symptom assessment and management

This article reviews how to assess and manage several symptoms commonly encountered by neurologists who care for patients with advanced illness. Scientifically validated guidelines are reviewed and practical advice is offered on how to manage pain, nausea and vomiting, dyspnea, and respiratory secretions at the end of life. The role of the neurologist as a provider of end of life care is discussed including suggestions for communicating with patients and families. This article concludes with a review of when sedation may be offered within the purview of good palliative care to patients who are imminently dying.

Antidepressants in the management of cancer pain

Most patients who have been diagnosed with cancer will experience pain at some point during the course of their disease. Often, opioid analgesics are not enough to completely alleviate the patient's pain and the selection of appropriate adjunct analgesic agents is critical. This article reviews the mechanisms of action and analgesic effects of several classes of antidepressants to enable the clinician to select the appropriate agent for the patient.