The use of antidepressants in the treatment of chronic pain. A review of the current evidence

Intrathecal tri-cyclic antidepressants produce spinal anesthesia

Tri-cyclic antidepressants (TCAs) have been widely used in treating major depressive disorders. Recent studies further demonstrated that TCAs have potent sodium channel blocking effect, and amitriptyline, one of the TCAs, has a potent spinal anesthetic effect. The aim of the study was to evaluate the spinal anesthetic effect of various TCAs and to see whether these TCAs could likewise act as local anesthetics after a single intrathecal injection. Bupivacaine, a potent and long-acting traditional local anesthetic, acted as control. The spinal anesthetic effect of nine TCAs (amitriptyline, doxepin, imipramine, trimipramine, clomipramine, protriptyline, desipramine, nortriptyline, and amoxapine) and three traditional local anesthetics (bupivacaine, lidocaine, and mepivacaine) was evaluated in rats and so were dose-response studies of amitriptyline, bupivacaine, and lidocaine. Under a given concentration of 5mM, bupivacaine had the most potent spinal blockade of motor, propioception, and nociception (P<0.001) and the longest duration of action of nociception (P<0.01) among the three traditional local anesthetics. Under this concentration, amitriptyline had a similar potency but longer duration of spinal blockade of motor, propioception, and nociception (P<0.001) than did bupivacaine, whereas several other TCAs had similar or less potencies of spinal blockade than did bupivacaine. In dose-response studies, amitriptyline had a more potent (P<0.005) and longer duration (P<0.001) of spinal blockade than did bupivacaine. We concluded that intrathecal amitriptyline had a more potent and longer duration of spinal anesthetic effect than did bupivacaine, whereas several other TCAs had similar or less potencies than did bupivacaine.

Functional dyspepsia: drugs for new (and old) therapeutic targets

The therapeutic management of functional dyspepsia remains a major challenge for the gastroenterologist. Current therapies available are based on putative underlying pathophysiologic mechanisms, including gastric acid sensitivity, slow gastric emptying and Helicobacter pylori infection, but only a small proportion of patients achieve symptomatic benefit from these therapeutic approaches. Relatively novel mechanistic concepts under testing include impaired gastric accomodation, visceral hypersensitivity, and central nervous system dysfunction. Serotonergic modulators (e.g. the 5-HT4 agonist tegaserod, the 5-HT3 antagonist alosetron and the 5-HT1P agonist sumatriptan), CCK-1 antagonists (e.g. dexloxiglumide), opioid agonists (e.g. asimadoline), N-methyl-D-aspartate (NMDA) receptor antagonists (e.g dextromethorphan), neurokinin antagonists (e.g. talnetant), capsaicin-like agents and antidepressants are among the agents currently under investigation. It seems unlikely, however, that targeting a single mechanism with an individual drug will result in complete symptom remission in most cases.

Management of insomnia in patients with chronic pain conditions

The management of insomnia in patients experiencing chronic pain requires careful evaluation, good diagnostic skills, familiarity with cognitive-behavioural interventions and a sound knowledge of pharmacological treatments. Sleep disorders are characterised by a circular interrelationship with chronic pain such that pain leads to sleep disorders and sleep disorders increase the perception of pain. Sleep disorders in individuals with chronic pain remain under-reported, under-diagnosed and under-treated, which may lead--together with the individual's emotional, cognitive and behavioural maladaptive responses--to the frequent development of chronic sleep disorders. The moderately positive relationship between pain severity and sleep complaints, and the specificity of pain-related arousal and mediating variables such as depression, illustrate that insomnia in relation to chronic pain is multifaceted and poorly understood. This may explain the limited success of the available treatments. This article discusses the evaluation of patients with chronic pain and insomnia and the available pharmacological and nonpharmacological interventions to manage the sleep disorder. Non-pharmacological interventions should not be considered as single interventions, but in association with one another. Some non-pharmacological interventions especially the cognitive and behavioural approaches, can be easily implemented in general practice (e.g. stimulus control, sleep restriction, imagery training and progressive muscle relaxation). Hypnotics are routinely prescribed in the medically ill, regardless of their adverse effects; however, their long-term efficacy is not supported by robust evidence. Antidepressants provide an interesting alternative to hypnotics, since they can improve pain perception as well as sleep disorders in selected patients. Sedative antipsychotics can be considered for sleep disturbances in those patients exhibiting psychotic features, or for those with contraindications to benzodiazepines. Low doses of sedative antipsychotics may improve chronic insomnia in the elderly. However, no intervention is likely to be effective unless a good physician-patient relationship is developed.

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.

Potentiation of imipramine-induced antinociception by nicotine in the formalin test

In this study, the effect of cholinergic agents on imipramine antinociception in mice, in the formalin test, has been investigated. Intraperitoneal (i.p.) administration of different doses of imipramine (2.5, 5, 10, 20 and 30 mg/kg) or nicotine (0.25, 0.5, 0.75 and 1 mg/kg) induced a dose dependent antinociception in both the first and second phases of the formalin test in mice. The combination of imipramine with doses of 0.5 and 0.75 mg/kg of nicotine showed a potentiated response, in both phases of the test. However, neither hexamethonium (5 and 10 mg/kg), atropine (0.25 mg/kg) or mecamylamine (0.25 mg/kg) altered the antinociception induced by imipramine. It is concluded that nicotinic receptor activation but not the cholinergic muscarinic mechanism is involved in the imipramine-induced antinociception.

Antinociceptive effects of tricyclic antidepressants and their noradrenergic metabolites

This study evaluates the antinociceptive effect of several tricyclic antidepressants in four nociceptive tests which employ either thermal (hot plate and tail flick tests) or chemical (formalin and acetic acid tests) stimuli. Forced swimming test was also performed as a model of depression and an activity test was also performed. Mixed antidepressants in current clinical use: amitriptyline, imipramine and clorimipramine and their respective main secondary metabolites which preferentially inhibit noradrenaline reuptake: nortriptyline, desipramine and desmethylclorimipramine, were tested (2.5-20 mg/kg, i.p.) in mice. The results show a stronger antinociceptive effect in chemical tests induced by all the drugs, compared with thermal tests. The doses needed to produce antinociception were lower than those inducing an antidepressive effect, both effects being mutually independent. The overall results show that preferentially noradrenergic tricyclics induced an antinociceptive effect comparable with that of mixed tricyclics, indicating that noradrenaline reuptake plays an important role in tricyclic-induced antinociception.

Adenosine receptor agonists or antagonists alter antinociception, but did not show an interaction with imipramine-induced antinociception in the formalin test in mice

In this study, the antinociceptive effect of imipramine and adenosine agents, and interactions between imipramine with adenosine drugs in mice in the formalin test, have been investigated. Intraperitoneal administration of different doses of imipramine (10, 20, 30 and 40 mg/kg) induced a dose dependent antinociception in mice, in both the first and second phases of the formalin test. The adenosine A(1) receptor agonists, R-(N(6)-phenylisopropyl)-adenosine (0.015, 0.03 and 0.1 mg/kg) and 5'-N-ethylcarboxamide adenosine (0.001, 0.005, 0.01 mg/kg), but not 2-chloroadenosine (0.1 and 0.5 mg/kg), and the adenosine receptor antagonist, 8-phenyltheophylline (0.1, 0.5 and 1 mg/kg), but not 1,3-dipropyl-7-methyl-xanthine (0.5 and 5 mg/kg), also produced an antinociceptive response. Lower dose of the adenosine receptor antagonist theophylline induced antinociception, while a higher dose of the drug caused hyperalgesia. Theophylline reduced the response induced by imipramine. It is concluded that adenosine systems are not involved in imipramine responses in the formalin test.

The assessment and management of chronic pain in children

Chronic pain in children and adolescents is frequently misdiagnosed by caregivers. It is not treated until it results in the loss of routine ability and function. Chronic pain is often associated with underlying diseases commonly seen in childhood, including sickle cell disease, malignancy, rheumatologic disorders, inflammatory bowel disease, trauma, and states where there is no identifiable etiology. Chronic pain differs from acute pain in that it serves no useful function. Untreated or under-treated chronic pain will result in the unnecessary suffering of the patient, disruption of family routine, and cohesiveness and restriction of the child's daily activities, thereby increasing long-term disability. Accurate and repeated assessment of chronic pain is required for therapy to be effective. Assessment of chronic pain in children is difficult due to their developing cognitive abilities. The assessment of childhood pain varies with the child's age, type of pain, situation, and prior painful experiences. Assessment tools such as the Varni-Thompson Pediatric Pain Questionnaire and the Visual Analog Scale are helpful for both the patient and physician in helping to identify situations that precipitate pain, to rate the level of pain and determine if therapy has been effective. Documentation of pain assessments and the effectiveness of interventions in the medical record should be included as a routine part of all patient records. Most caregivers have extensive experience in the treatment of acute pain in children but are often not comfortable with the management of complicated and chronic pain states. The therapy for chronic pain in children is multifactorial. It can include agents from multiple classes of pharmacologic agents (nonsteroidal anti-inflammatory drugs, opioids, tricyclic antidepressants, and antineuroleptics) nonconventional therapies (acupuncture and pressure and aromatherapy), as well as herbal and homeopathic remedies.

Antidepressants for chronic neuropathic pain

Tricyclic antidepressants have been used to manage pain for several decades, and are superior treatments for some patients suffering from neuropathic pain. Unfortunately, older antidepressants have dose-limiting side effects that can lead to drug intolerance. The most common are anticholinergic side effects, although some patients experience sexual dysfunction. Cognitive impairment, sedation, and orthostatic hypotension also are relatively common. Taking an overdose of tricyclic antidepressants can be lethal in overdose. Several weeks of therapy may be required before antinociception occurs, but tricyclic antidepressants in optimal doses appear to be the most effective treatment for neuropathic pain; this is supported by systematic reviews comparing them with other agents. Newer medications such as atypical antidepressants and anticonvulsants may be overtaking older antidepressants, but they should not be overlooked as important options for the management of pain.

Assessment and treatment of comorbid psychiatric disorders in opioid-dependent patients

The purpose of this article is to provide a review of the prevalence, assessment, and treatment of common psychiatric disorders found among patients with opioid dependence. Dependence on opioids can include both persons who are physically dependent on opioids and persons who fulfill the criteria for a syndrome of opioid dependence, such as that found in the Diagnostic and Statistical Manual, fourth edition (DSM-IV). The latter grouping of persons typically abuse illicit opioids, and prevalence of comorbid conditions and approaches in diagnosis and treatment have been studied in these patients. High rates of other psychiatric disorders--both other substance-use disorders as well as non-substance-use psychiatric disorders--have been reported. The most common non-substance-use psychiatric disorders are depressive, anxiety, and personality disorders. When evaluating and planning treatment of opioid-dependent patients with concurrent psychiatric symptoms, it is important to determine if such symptoms are independent of the substance use or substance induced. In the former case, treatment should follow routine clinical practice, whereas in the latter case, treatment stability in substance use should be the first therapeutic step. The presence of a pain condition can further complicate assessment and treatment, as either pain itself or treatments used for pain may produce symptoms that overlap with psychiatric disorders.

Efficacy of oral doxepin and piroxicam treatment for interstitial cystitis

OBJECTIVE

To establish the efficacy of a multidrug oral treatment with the tricyclic antidepressant agent doxepin and the cyclooxygenase (COX) inhibitor piroxicam in patients with interstitial cystitis (IC), who had failed standard therapy in an open, prospective, nonrandomized study.

METHODS

A total of 37 patients diagnosed with IC received 75 mg doxepin and 40 mg piroxicam daily. The treatment was termed DOXCAM. Effectiveness of therapy was assessed with frequency-volume charts, an IC symptom score and with cystometry prior to treatment, 8 weeks after the start and 4 weeks after termination of drug treatment.

RESULTS

Medication was not tolerated by five patients. Twenty-six of 32 patients have experienced virtual total remission of symptoms (81%) and six patients had significant relief (19%). DOXCAM treatment resulted in a significant percent decrease in pain (65% versus 21%). Daytime frequency decreased from 17.6+/-5.7 to 11.3+/-3.6 voids while nocturia did not improve significantly. Twenty-three of the 26 patients who became symptom free and four of the six patients who showed significant improvement had a return of symptoms after cessation of therapy.

CONCLUSION

It is reasonable to consider oral treatment with DOXCAM in those patients who have failed first-line therapies.

Palliative care and the child with cancer

There is a growing awareness and a WHO directive that the palliative care paradigm should be incorporated into the care of all children with cancer, irrespective of geographic location. The barriers to pediatric palliative care identified by pediatric oncologists [3] are lack of formal courses in pediatric palliative care, a high reliance on trial-and-error learning, lack of strong role models, and lack of access to a pain and palliative care service. These barriers must be overcome.

Spinal cord injury medicine. 2. Medical complications after spinal cord injury: Identification and management

This is a self-directed learning module that reviews medical complications associated with spinal cord injury (SCI). It is part of a chapter on SCI medicine in the Self-Directed Physiatric Educational Program for practitioners and trainees in physical medicine and rehabilitation. This article includes discussion of common medical complications that impact rehabilitation and long-term follow-up for individuals with SCI. Issues addressed include the rehabilitation approach to SCI individuals with pressure ulcers, unilateral lower-extremity swelling (deep venous thrombosis, heterotopic ossification, fractures), along with the pathophysiology, assessment, and treatment of spasticity, autonomic dysreflexia, orthostatic hypotension, and pain.

OVERALL ARTICLE OBJECTIVE

To describe diagnostic and treatment approaches for medical complications common to individuals with SCI.

Refractory chronic pain

Refractory chronic pain is a significant public health problem and frustrating to everyone affected by it. All physicians can participate in the care of these patients, but psychiatrists should take a leading role in their care. A comprehensive approach offers hope and increases the opportunities for successful treatment. Each perspective of an interdisciplinary formulation has a unique logic that defines specific methods for designing treatment for the patient with refractory chronic pain. The patient does not have to fit into one theoretic approach or model to receive and accept treatment. The patient's diagnoses are based on the formulation, which then directs treatment along rational directions. The linkages and interactions of a patient's diagnoses can then be investigated within a framework that includes the entire person and not just his or her biochemistry. If a patient's suffering persists, other factors must be considered that may have been overlooked before the treatment plan is abandoned or modified. Usually these factors are within one of the perspectives initially thought to be less important. A new combination of approaches is then required to treat the patient successfully. The perspectives appreciate not only that the patient is struggling through important life events but also that he is a person composed of vulnerabilities and strengths, having made many choices and afflicted by diseases.

Tension headaches and muscle tension: is there a role for magnesium?

Although many theories and hypotheses have been offered for the etiology of tension-type headache (TH), no one previous hypothesis seems to adequately explain TH. This may, in large measure, account for why it is often difficult to effectively treat TH. Herein, we review current and old hypotheses of TH and offer a new hypothesis which is consistent with what is known about TH. We show that magnesium (Mg) metabolism may be pivotal in both the etiology and treatment of TH. Measurement of serum ionized Mg2+ (IMg2+) levels and brain intracellular free Mg2+ ([Mg2+]i) appear to offer excellent methods for establishing the validity of our hypothesis. Since approximately 70% of patients who have a TH exhibit muscular tightness and tenderness, it is distinctly possible that problems in Mg metabolism and dietary intake are the links to concomitant muscle tension and TH. The significance of release of pain mediators, muscle cramps, muscle strains (and damage) and muscle tension to TH, and its relationship to Mg metabolism, are reviewed. These are all associated with a Mg-deficient state. It seems clear from the available data that TH's are more associated with muscle tension or scalp tension than any other headache type. From the data available, Mg supplementation appears to be of great benefit in many of these situations. We believe there is a great need for clinicians to examine Mg2+ metabolism, bioavailable Mg2+ in muscle tissues and blood, and the effectiveness of Mg salts (in a double-blinded, placebo-controlled manner) in subjects with TH and muscle tension.

Adjunctive agents in the management of chronic pain

Chronic pain syndromes include cancer-related pain, postherpetic neuralgia, painful diabetic neuropathy, and central poststroke pain and are common in the elderly. Adjunctive (or adjuvant) analgesics, defined as drugs that do not contain acetaminophen and those not classified as nonsteroidal antiinflammatory or opioid agents, play a role in the management of chronic pain. The term "adjunctive" (or "adjuvant") is a misnomer as several of these agents may constitute first-line therapy for many chronic pain syndromes. Tricyclic antidepressants have formed the backbone of therapy for chronic neuropathic pain for years. However, the difficulty with using agents of this class, due to their clinically significant adverse-event potential, has led to the evaluation of other agents, most notably, the antiepileptic drugs. The most useful are gabapentin, carbamazepine, and lamotrigine. In selected patients, baclofen, mexiletine, and clonidine may be useful as well. Cancer-related pain may respond substantially to corticosteroids, and pain associated with bone metastases to parenteral bisphosphonates and strontium. Practitioners should consider these alternative agents when treating chronic pain.

A comparative trial of botulinum toxin type A and methylprednisolone for the treatment of tension-type headache

Tension-type headache (TH) is a common condition, the pathophysiology of which remains undetermined. Evidence implicates sustained contraction of pericranial muscles to be a major cause. A recent preliminary study demonstrated the effectiveness of botulinum toxin type A (BTX-A) in patients suffering from chronic TH. To further investigate this, we performed a study to compare the efficacy of BTX-A with the steroid methylprednisolone (both administered with the local anesthetic lidocaine), when administered by injection into the tender points of cranial muscles in patients with TH. A significant decrease in the median pain score (assessed using a standard visual analogue scale ) was observed at 60 days post injection of BTX-A compared with the pain score achieved following steroid therapy. All patients treated with BTX-A experienced a gradual decrease in median pain severity scores at 30 days and 60 days post treatment. The beneficial effects of BTX-A therapy continued to improve 60 days following injection, whereas the effects of steroid therapy at this time point began to decline. This study clearly demonstrates the effectiveness of BTX-A for the treatment of TH.

Involvement of GABAergic systems in manifestation of pharmacological activity of desipramine

We have conducted this study to elucidate the influence of GABAergic systems on manifestation of pharmacological activity of desipramine using both pharmacological and electrophysiological methods. Desipramine (20 mg/kg, i.p.) significantly blocked the adjuvant-induced thermal hyperalgesia, which was facilitated by treatment with the GABA(A) antagonist picrotoxin (2 mg/kg, i.p.) or the GABA(B) antagonist saclofen (2 mg/kg, i.p.). This analgesic effect of desipramine was antagonized by post-treatment with picrotoxin or saclofen. However, none of these compounds showed any effect in normal animals without adjuvant-induced inflammation. In a slice preparation of the hippocampus, treatment with GABA (10(-5)-5 x 10(-4) M), baclofen (10(-5)-10(-4) M) or muscimol (10(-5)-10(-4) M) inhibited the field potential evoked in pyramidal neurons by Schaffer collateral stimulation. The inhibitory effect of GABA was facilitated by concurrent application of desipramine, carbamazepine or diazepam at a concentration of 5 x 10(-5)-2 x 10(-4) M. The rank of order of facilitation is: desipramine > carbamazepine > diazepam. Desipramine also enhanced the inhibitory effect of baclofen and muscimol. These results suggest that desipramine causes GABAergic systems to activate still more, and this phenomenon appears to be involved in manifestation of the pharmacological activity of desipramine such as antinociception.

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.

Effect of alpha-adrenoceptor agents on imipramine-induced antinociception in nerve-ligated mice

In this study, the effects of adrenoceptor agonists and antagonists on antinociception induced by imipramine in sciatic-nerve-ligated mice were investigated. The response of different doses of morphine, imipramine and adrenoceptor agonists and antagonists was examined 14 days after unilateral nerve-ligation in the hot-plate test. Intraperitoneal injection of different doses of morphine (3, 6 and 9 mg/kg), imipramine (10, 20 and 40 mg/kg), the alpha(2)-adrenoceptor agonist, clonidine (0.05, 0.1 and 0.2 mg/kg) or the alpha(1)-adrenoceptor agonist, phenylephrine (2, 4 and 8 mg/kg) induced dose-related antinociception in both intact and nerve-ligated mice. The antinociception induced by morphine but not that of imipramine, clonidine or phenylephrine, in nerve-ligated mice was significantly less than that induced in intact animals. Imipramine in combination with clonidine tends to induce a higher response, but the combination of imipramine with phenylephrine did not lead to significant potentiation. The alpha(2)-adrenoceptor antagonist, yohimbine, reduced the response induced by imipramine or imipramine plus clonidine in intact and nerve-ligated animals. However, the alpha(1)-adrenoceptor antagonist, prazosin, did not alter imipramine response. It may be concluded that imipramine induced antinociception in both intact and nerve-ligated mice through an alpha(2)-adrenoceptor mechanism(s).

Antinociceptive effect of clomipramine in monoarthritic rats as revealed by the paw pressure test and the C-fiber-evoked reflex

The antinociceptive effect of clomipramine was studied in monoarthritic rats by using the paw pressure test and the C-fiber-evoked reflex. Monoarthritis was produced by intra-articular injection of complete Freund's adjuvant into the tibio-tarsal joint. Joint circumference as well as vocalization threshold to graded paw pressure were evaluated weekly during a 14-week period after the intra-articular injection. At week 8, monoarthritic and vehicle-injected control rats were given either clomipramine or saline and both the paw pressure threshold and inhibition of the C-fiber-evoked reflex response were evaluated. Results showed that (i) 1.5, 3.0, and 6.0 mg/kg, i.v. of clomipramine induced significantly greater dose-dependent antinociception to paw pressure testing in the monoarthritic group, as compared to the control one; and (ii) 0.75, 1.5, 3.0, and 6.0 mg/kg, i.v. of clomipramine exerted significantly higher dose-dependent inhibition of the C-reflex activity in monoarthritic rats than in controls. Results suggest that the higher sensitivity to clomipramine in monoarthritic rats could be related to adaptive changes occurring in monoamine metabolism or in other neurotransmitter systems during chronic pain.

Potentiation of the antinociceptive effect of clomipramine by a 5-ht(1A) antagonist in neuropathic pain in rats

The benefit of antidepressant treatment in human neuropathic pain is now well documented, but the effect is limited and slow to appear. It has been demonstrated that the association of a 5-HT(1A) antagonist and a serotoninergic antidepressant reduced the delay of action and increases the thymoanaleptic effect of the drug. The purpose of this work was to evaluate the combination of an antidepressant and a 5-HT(1A) antagonist in animal models of chronic neuropathic pain. We studied the antinociceptive effect of the co-administration of clomipramine and a 5-HT(1A) antagonist (WAY 100,635) in a pain test applied in normal rats and in two models of neurogenic sustained pain (mononeuropathic and diabetic rats). The results show an increase in the antinociceptive effect of acutely injected clomipramine due to WAY 100,635 in these models, which is majored when the two drugs are repeatedly injected. The 5-HT(1A) antagonist reduced the delay of onset and increased the maximal antinociceptive effect of clomipramine. These new findings argue for using the combination of an antidepressant and a 5-HT(1A) antagonist in human neuropathic pain therapy.

The effects of antidepressants on obstructed and unobstructed gait in healthy elderly people

BACKGROUND

Elderly patients treated with antidepressants for depression are at high risk for injury due to falling. The primary purpose of this study was to determine the effects of amitriptyline, desipramine, and paroxetine on the gait of healthy elderly subjects during unobstructed and obstructed (i.e., stepping over obstacles) gait. Psychomotor and mood tests were also performed.

METHODS

A randomized, crossover, four-period, double-blind, placebo-controlled laboratory trial was performed. Twelve healthy elderly subjects (average age, 67 years; range, 65-72 years) were tested. Subjects were assigned the three antidepressant drugs or a placebo in a random order. Single doses of amitriptyline 50 mg, desipramine 50 mg, paroxetine 20 mg, or placebo were given 4 hours prior to gait testing. Temporal-distance measures and kinematics of the lower trailing limb (i.e., limb going over obstacle last) were obtained.

RESULTS

Compared with placebo, amitriptyline significantly reduced gait velocity by as much as 8.0% (p = .028), cadence by as much as 4.9% (p = .012), angular velocity of hip flexion by as much as 10.0% (p = .004), and angular velocity of knee flexion by as much as 8.3% (p = 018) during the crossing strides when stepping over obstacles. Except for knee flexion angle, unobstructed gait was not affected. Amitriptyline affected integrative capacity of the central nervous system (CNS) and ability to concentrate as measured by psychomotor and mood tests.

CONCLUSIONS

The results for amitriptyline suggest that the subjects slowed their obstacle crossing speeds as a result of reduced CNS integrative capacities. Neither paroxetine nor desipramine significantly affected gait, psychomotor function, or mood.

GABA(B) receptor mechanism and imipramine-induced antinociception in ligated and non-ligated mice

This study concerned the effects of GABA(B) receptor agents on imipramine-induced antinociception in ligated and non-ligated mice in hot-plate test. The data showed that different doses of morphine (3, 6 and 9 mg/kg) induced a dose-dependent antinociception in non-ligated or ligated mice. However, the opioid response was decreased in the ligated animals. Intracerebroventricular (i.c.v.) administration of imipramine (5, 10, 20 and 40 microg/mouse) did not induce antinociception in either non-ligated or ligated mice. However, the response induced in the ligated mice was less than that induced in the non-ligated animals. Intraperitoneal (i.p.) administration of imipramine (10, 20, 30 and 40 mg/kg) induced antinociception in both ligated and non-ligated animals. The responses to the drug were not significantly different in the two groups. Administration of baclofen either i.c.v. (0.125, 0.25 and 0. 5 microg/mouse) or i.p. (0.5, 1, 2 and 4 mg/kg) induced antinociception. The response to the drug was not significantly different in ligated and non-ligated mice. I.c.v. administration of a lower dose of baclofen (0.125 microg/mouse) with different doses of imipramine (2.5, 5 and 10 mg/kg) potentiates the response of imipramine. This effect was reduced by i.c.v. injection of GABA(B) receptor antagonist, CGP35348 [P-(3-aminopropyl)-p-diethoxymethyl-phosphinic acid] (20 microg/mouse). The higher dose of antagonist (20 microg/mouse) also decreased the response induced by baclofen or imipramine. CGP35348 itself (2.5, 5, 10 and 20 microg/mouse) induced dose-dependent antinociception with no significant difference in the ligated and non-ligated mice. It is concluded that a GABA receptor mechanism(s) may modulate the antidepressant-induced antinociception.

Opioid and Nonopioid Therapy in Cancer Pain: The Traditional and the New

Management of cancer pain has made sidnificant progress in recent years, partly due to the Agency for Health Care Policy and Research (AHCPR) guidelines, but mostly it seems to be due to the death and dying movement in the world. However, cancer pain on occasion poses significant problems and needs accurate diganosis and appropriate intervention. Pharmacotherapy remains the mainstay of treating cancer pain. Most cancer pain syndromes present with moderate to severe pain, associated with several comorbid problems necessitating the multidisciplinary approach to optimally treat it. The psychologic factors associated wth serious illness, terminal prognoses, and dying complicate the scenario even more as compared with that of nonmalignant pain. Although such patients are entitled to more aggressive analgesic therapy, it is unfortunate that this is not achieved in a significant percentage of cases. In this review, we address some of the above issues and attempt to summarize the traditional pharmacologic therapies highlighting their modern modes of implementation in cancer pain management. Special emphasis on the state-of-the art innovations in this field wil be noted.

Amitriptyline reduces myofascial tenderness in patients with chronic tension-type headache

The tricyclic anti-depressant amitriptyline is widely used in the treatment of chronic tension-type headache. The aim of the present study was to investigate whether the analgesic effect is caused by a reduction of muscle pain or by a general reduction of pain sensitivity. Thirty-three non-depressed patients with chronic tension-type headache were treated with amitriptyline 75 mg/day and with the highly selective serotonin reuptake inhibitor citalopram 20 mg/day in a 32-week, double-blind, placebo-controlled, three-way crossover study. At the end of each treatment period, actual headache intensity and pericranial myofascial tenderness were recorded, pressure pain detection and tolerance thresholds were measured in the finger and in the temporal region and the electrical pain threshold was measured at the labial commissure. Amitriptyline reduced tenderness and headache intensity significantly more than placebo (P=0.01 and P=0.04, respectively). The reduction in tenderness could be ascribed solely to the group of patients who responded to amitriptyline treatment by at least 30% reduction in headache while tenderness was unchanged in non-responders. Amitriptyline did not affect pressure or electrical pain thresholds at any of the examined locations. Citalopram had no significant effect on any of the examined parameters. These findings indicate that amitriptyline elicits its analgesic effect in chronic myofascial pain by reducing the transmission of painful stimuli from myofascial tissues rather than by reducing overall pain sensitivity. We suggest that this effect is caused by a segmental reduction of central sensitization in combination with a peripheral anti-nociceptive action.

Tramadol relieves thermal hyperalgesia in rats with chronic constriction injury of the sciatic nerve

The present study was designed to test whether tramadol is effective in the control of neuropathic pain in rats. Chronic constriction injury (CCI) of the sciatic nerve was induced over the left hind limb in male Sprague-Dawley rats. Identical surgery was performed on the opposite side except that the sciatic nerve was not ligated (sham surgery). Paw withdrawal latency (PWL) to heat was tested for each hind paw 1 day before surgery and on the 4th day after surgery to ensure the development of thermal hyperalgesia. In the acute treatment groups, saline or tramadol was administered subcutaneously at doses of 10, 20 or 30 mg/kg, and PWLs were measured 30, 60, 90, 120, 150 and 180 min after treatment. In the semi-chronic treatment groups, continuous systemic administration of tramadol 40 mg/kg/day or saline for 7 days was provided at a uniform rate via osmotic mini pumps. Tramadol reversed PWL in a dose-dependent manner in the acute treatment groups. PWLs were significantly reversed at 2 days after tramadol infusion, and this effect was sustained throughout the remainder of the treatment period in comparison with the saline group. Tramadol also resulted in a decreased sensitivity to thermal stimulus on the sham limb both in acute and semi-chronic administration. We conclude that both acute and semi-chronic tramadol treatment relieves thermal hyperalgesia effectively in rats with CCI of the sciatic nerve. This indicates that tramadol shows promise as a potential treatment for relief of neuropathic pain in humans.

Physical medicine modalities for mechanical neck disorders

OBJECTIVES

Multiple physical medicine modalities are commonly included as part of therapeutic interventions for mechanical neck disorders (neck pain). The objective of this review was to assess the effects of physical medicine modalities for pain in adults with mechanical neck disorders.

SEARCH STRATEGY

We searched Medline, Embase, Chirolars, Index to Chiropractic Literature, Cinahl, Science Citation Index, Conference Proceedings Index, National Technical Information Services and reference lists of the retrieved articles from 1985 to December 1993 and we contacted content experts.

SELECTION CRITERIA

Randomised trials and controlled trials of physical medicine modalities in adults with mechanical neck disorder.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trial quality and two reviewers independently extracted data. Investigators were contacted to obtain information or data that could not be found in the published reports.

MAIN RESULTS

Thirteen trials were included. The overall quality of the included trials was generally good. Two trials using electromagnetic therapy produced a significant reduction in pain (p <0.01) with three to four weeks of daily (eight hours per day) therapy sessions; and three using laser therapy did not differ significantly from a placebo (p=0.20) for six to 10 sessions of treatment. Not enough scientific testing exists to clearly determine the effectiveness of other therapies. This includes treatments such as exercise, traction, acupuncture, heat / cold applications, electrotherapies, cervical orthoses and chronic pain / cognitive behavioural rehabilitation strategies.

REVIEWER'S CONCLUSIONS

There is little information available from trials to support the use of physical medicine modalities for mechanical neck pain. There is some support for the use of electromagnetic therapy and against the use of laser therapy with respect to pain reduction.

Serotonin-mediated increases in the extracellular levels of beta-endorphin in the arcuate nucleus and nucleus accumbens: a microdialysis study

Although the involvement of both endogenous opioid and serotonergic systems in modulation of pain and emotion was suggested, the neurochemical interaction between these systems in the brain has not previously been studied directly. Herein, the effects of the local application of serotonin (5-HT) and fluoxetine (a 5-HT reuptake inhibitor) on extracellular levels of beta-endorphin in the arcuate nucleus and nucleus accumbens were assessed in freely moving rats using in vivo microdialysis. The mean basal concentrations of beta-endorphin in dialysates obtained from the arcuate nucleus and nucleus accumbens were 259.9 and 143.3 pM, respectively. Specific lesion of the serotonergic system by 5,7-dihydroxytryptamine (5,7-DHT) caused a significant decrease in these dialysate beta-endorphin levels. When 5-HT (0.25-5 microM) was added to the perfusion solution, the levels of beta-endorphin in the dialysate from the arcuate nucleus increased (186-296% of baseline), in a concentration-dependent manner. In the nucleus accumbens, 0.5 and 2 microM 5-HT in the perfusion fluid did not affect the levels of beta-endorphin in the dialysate, whereas 5 and 10 microM 5-HT caused an increase of approximately 190% of baseline. When fluoxetine (250 microM) was present in the perfusing solution, the levels of beta-endorphin in the dialysates from the arcuate nucleus and nucleus accumbens increased two- to threefold. This effect was not obtained in the 5,7-DHT-lesioned rats. Thus, 5-HT, either endogenously or exogenously delivered, appears to facilitate the release of beta-endorphin in the arcuate nucleus and nucleus accumbens. This indication of an interaction between serotonergic and endorphinic systems may be relevant for assessing pain and mood disorder circuits and the mode of action of antidepressant drugs.

Cyclic vomiting syndrome in adults: clinical features and response to tricyclic antidepressants

OBJECTIVE

Cyclic vomiting syndrome (CVS) has been described infrequently in adults, and treatment in both children and adults remains unsatisfactory. We report clinical features of a group of adults with CVS and anecdotal outcome from open-label treatment with tricyclic antidepressants, medications that have some efficacy in other unexplained gastrointestinal disorders.

METHODS

Clinical data were examined from 17 adult patients with CVS seen over a 10-yr period, each having been treated with a tricyclic antidepressant. Outpatient records were reviewed, clinical outcome was extracted using a priori criteria, and findings were compared with 37 patients having usual functional nausea and vomiting who also received tricyclic antidepressant therapy.

RESULTS

Symptoms in CVS began at age 35 yr (range 14-73 yr); the average episode length was 6 days (range 1-21 days) and the symptom-free interval averaged 3.1 months (range 0.5-6 months). Vomiting cycles typically began without warning, and fewer than one-third of the subjects reported a prodrome or potential trigger event, such as menstrual periods, pregnancy, or large meals. Sleep was seemingly beneficial in 23.5%. Tricyclic antidepressant therapy was associated with complete remission in 17.6% and partial response in 58.8%, but was less effective than for functional nausea and vomiting (p = 0.02).

CONCLUSIONS

CVS is a rare diagnosis with distinctive features in adults. Duration of episodes and cycles varies considerably across subjects. In open-label, uncontrolled use, tricyclic antidepressants appear beneficial for some subjects but are less effective in CVS than in chronic, persistent functional nausea and vomiting.

Analgesic effect of oral ketamine in chronic neuropathic pain of spinal origin: a case report

Ketamine is an injectable anesthetic induction agent that has been reported to have analgesic activity in pain from a variety of mechanisms, but predominantly in neuralgic and dysesthetic neuropathic pain. In this case report we illustrate the effectiveness of ketamine in a patient with neuropathic pain resulting from cauda equina trauma. Among the issues addressed are the role of pretreatment with haloperidol to prevent ketamine-induced psychomimetic effects, the potential for fewer side effects and a need for lower doses when ketamine is administered orally, and the need for further study regarding appropriate monitoring parameters during the titration phase. Oral ketamine can be effective in treatment refractory chronic neuropathic pain of spinal origin.

Psychological conditions diagnosed among veterans seeking Department of Defense Care for Gulf War-related health concerns

The Comprehensive Clinical Evaluation Program is a US military program that provides a voluntary, clinically oriented evaluation for Gulf War health concerns. This article presents administrative data on psychological conditions (as coded using the International Classification of Diseases, 9th Revision) from the first year of the program. The most commonly diagnosed psychological conditions were medically unexplained physical-symptom syndromes; depression and anxiety, including post-traumatic stress disorder; and alcohol abuse or dependence. Psychological conditions were significantly related to a higher number of workdays lost, and the 19% of veterans with a primary diagnosis of a psychological condition reported 28% of the lost workdays among veteran who participated. Stressful Gulf War experiences were weakly but significantly related to psychological conditions. We conclude that among Gulf War veterans seeking evaluation for Gulf War-related health concerns, psychological conditions are common and are associated with important occupational morbidity.

Effect of acute and chronic tramadol on [3H]-norepinephrine-uptake in rat cortical synaptosomes

1 Tramadol hydrochloride is a centrally acting opioid analgesic whose efficacy and potency is only five to ten times lower than that of morphine. Opioid, as well as non-opioid mechanisms, may participate in the analgesic activity of tramadol. 2 [3H]-NE uptake in isolated rat cortical synaptosomes was studied in the presence of tramadol, desipramine, methadone, and morphine. Desipramine and tramadol inhibited synaptosomal [3H]-NE uptake with apparent Kis of 7.3 +/- 0.66 and 1.4 +/- 0.0045 microM, respectively. Methadone was active at a 10-fold higher concentration (Ki: 87 +/- 5.6 microM). In contrast, morphine essentially failed to inhibit [3H]-5-HT uptake (Ki: 0.75 +/- 0.40 M). 3 Methadone, morphine, and tramadol were active in the hot plate test with ED50s of 6.2, 9.3, and 40 mg kg-1, respectively. 4 [3H]-NE uptake was examined in synaptosomes prepared from rats 30 min after receiving a single dose of morphine, methadone or tramadol. Only tramadol (31 mg kg-1, i.p.) decreased uptake of the transmitter, with an ED50 equal to that in the hot plate test. 5 Animals were chronically treated for 15 days with increasing doses of tramadol (20 to 125 mg kg-1, i.p.). Twenty-four hours after the last drug injection, a challenge dose of tramadol (40 mg kg-1, i.p.) was administered. Chronic tramadol was still able to reduce [3H]-NE uptake by 35%. 6 These results further support the hypothesis that [3H]-NE uptake inhibition may contribute to the antinociceptive effects of tramadol. The lack of tolerance in [3H]-NE uptake, together with the absence of behavioural alteration after chronic tramadol treatment proposes that tramadol holds potential over classical opioids in the treatment of pain disorders.

The use of analgesics in the management of pain in rheumatic diseases

Pain is the most common complaint of patients who see rheumatologists. In this article, the current treatment options for pain are reviewed; these include acetaminophen, nonsteroidal anti-inflammatory drugs, new specific cyclooxygenase-2 inhibitors, opioid analgesics, centrally acting muscle relaxants, antidepressants, and topical analgesics and counterirritants. The doses of medication and known adverse effects of these medications are highlighted.

The meeting of pain and depression: comorbidity in women

The higher prevalence of depression in women is coupled with a higher prevalence of pain complaints. Growing evidence suggests that the comorbidity of these conditions is also proportionately higher in women than men. This paper critically reviews the empirical findings relating to gender differences in comorbid pain and depression as well as findings in support of hypothesized etiologic factors that could explain why women may be more susceptible than men to comorbidity. The empirical evidence for biogenic, psychogenic, and sociogenic explanatory models is presented, and an integration of these models is proposed as a guideline to both research and clinical practice. In conclusion, it is argued that gender-differentiated treatment strategies are not clinically indicated at this time.

Differential effects of amitriptyline on perception of somatic and visceral stimulation in healthy humans

Tricyclic antidepressants treat chronic pain both in patients with somatic illness and with functional bowel disorders. We compared the effects of amitriptyline on perception of cutaneous and gastrointestinal stimulation to assess differential analgesic effects of tricyclics on somatic and visceral pain. Cutaneous electrical stimulation and rectal and esophageal distension were performed before and after 21 days of double-blind 50 mg amitriptyline vs. placebo in healthy volunteers. Amitriptyline increased currents that elicited cutaneous threshold, moderate discomfort, and moderate pain compared with basal (P < 0.05), whereas placebo had no effect. Amitriptyline had no effect on perception of rectal and esophageal distension and did not alter luminal compliance; thus the lack of effect on perception is not due to altered visceral elastic wall properties. In conclusion, amitriptyline reduces perception of cutaneous stimulation but does not alter visceral perception or compliance. This investigation demonstrates differential effects of tricyclics on somatic and visceral afferent function in healthy humans and provides insight into mechanisms of action in chronic pain both from somatic disease and from functional bowel disorders.

Effects of tricyclic antidepressants on mechanosensitive pelvic nerve afferent fibers innervating the rat colon

The aim of this study was to examine the effects of tricyclic antidepressants on responses of mechanosensitive afferent fibers innervating the rat colon. A total of 53 fibers in the decentralized S1 dorsal root were studied. The effects of the non-specific monoamine reuptake inhibitor imipramine (IMI), the noradrenaline reuptake inhibitor desipramine (DES), and the serotonin reuptake inhibitor clomipramine (CLO) were tested on responses of 22 mechanosensitive afferent fibers to noxious colorectal distension (CRD; 80 mmHg). Cumulative doses of 16 mg/kg of IMI, DES and of CLO reduced responses to noxious CRD to a mean 20%, 22% and 46% of control, respectively. The mean inhibitory doses of the three antidepressants did not differ significantly. Inhibitory effects were independent of potential effects on neurotransmitter reuptake: the effects of IMI and DES were not blocked by the adrenoreceptor antagonist phentolamine, and the effects of IMI and CLO were not affected by the serotonin receptor antagonist metergoline. Attenuation of afferent nerve activity was not mimicked by the anticholinergic glycopyrrolate; the cholinesterase inhibitor neostigmine did not attenuate the effect of IMI on responses to noxious CRD. Interestingly, the opioid receptor antagonist naloxone partially reversed the effects of IMI, and the NMDA receptor channel blocker MK-801 enhanced the inhibitory effects of DES and CLO. These results document that responses of mechanosensitive pelvic nerve afferent fibers to noxious CRD are significantly attenuated by tricyclic antidepressants, a peripheral action that may contribute to the beneficial effects of tricyclic antidepressants in treatment of irritable bowel syndrome.