Treatment of painful diabetic neuropathy with trazodone

PK/PD analysis of trazodone and gabapentin in neuropathic pain rodent models: Translational PK-PD modeling from nonclinical to clinical development

A pharmacokinetic/pharmacodynamic (PK/PD) model was developed to describe the time course of writhings after intraperitoneal injection of acetic acid in mice. The model was applied to investigate the antinociceptive effect of trazodone and gabapentin alone and in combination. Writhings time course was described by a transit compartment model with the delay due to the transit of the acetic acid being represented by a chain of intermediate compartments. In the drug-treated animals, the number of writhings decreases according to a k₂ factor linking drug concentration and antinociceptive effect. Compounds' potency parameters were 10.9 and 0.0459 L/μmoles/min for trazodone and gabapentin, respectively, indicating a much higher in vivo potency of trazodone in the PD writhing test. The PK/PD parameters were used to simulate the expected writhing counts in mice at combined doses without efficacy alone, assuming pharmacological additivity. Simulation results indicated that, at low dose combinations, experimental data were mostly below the simulated writhings median, suggesting possible synergic effect. Such hypothesis was tested by adding the γ parameter in the PK/PD model to represent the deviation from the assumption of no-interaction, leading to a reduction of the objective function compared to the additive model. On this basis, several simulations were performed to identify possible starting dose combinations of trazodone and gabapentin in humans, by selecting doses yielding systemic exposures close to those being synergic in the mouse. Simulations indicated that doses of 50-100 mg trazodone could enhance gabapentin antinociceptive effect in humans, supporting the development of a low dose combination for optimal analgesia treatment.

[Treatment of mental disorders caused or triggered by somatic and neurological diseases with the use of the multimodal antidepressant trazodone]

The purpose of this narrative review is to relate current data on the molecular mechanisms of action of trazodone with its clinical effects and applicability in mental disorders caused or triggered by somatic and neurological disease, according to available publications. In the article, the prospects for the use of the multimodal antidepressant trazodone are discussed in accordance with therapeutic targets. The latter are discussed in accordance with the typology of the mentioned above psychosomatic disorders. Trazodone is an antidepressant acting primarily due to the blockade of postsynaptic serotonin 5H2A- and 5H2C-receptors, as well as the blockade of serotonin reuptake, but also has affinity for a number of additional receptors. The drug has a favorable safety profile and a wide range of beneficial effects: antidepressive, somnolent, anxiolytic, anti-dysphoric and somatotropic. This makes it possible to influence a wide range of therapeutic targets in the structure of mental disorders caused or triggered by somatic and neurological diseases, carrying out safe and effective psychopharmacotherapy.

Efficacy and Safety of Low Doses of Trazodone in Patients Affected by Painful Diabetic Neuropathy and Treated with Gabapentin: A Randomized Controlled Pilot Study

BACKGROUND

Painful diabetic neuropathy is an important therapeutic challenge as the efficacy of analgesic drugs in this setting is still unsatisfactory. Monotherapy with available treatments is often not sufficient and a combination of drugs is necessary. Trazodone (TRZ) is a compound with a multi-modal mechanism of action, being a serotonin-2 antagonist/reuptake inhibitor developed and approved for the treatment of depression in several countries. Previous clinical trials suggest a possible beneficial effect of low doses of trazodone for the treatment of patients affected by painful diabetic neuropathy.

OBJECTIVE

This phase II study was designed to collect data on the efficacy and safety of low doses of TRZ combined with gabapentin after 8 weeks of treatment in patients affected by painful diabetic neuropathy.

METHODS

This was a randomized, double-blind, placebo-controlled, multi-center, international, prospective study. Male and female diabetic patients aged 18-75 years and affected by painful diabetic neuropathy were eligible for enrollment. Subjects were randomized (1:1:1 ratio) to TRZ30 (10 mg three times daily for 8 weeks) or TRZ60 (20 mg three times daily for 8 weeks) or placebo. Gabapentin as background therapy was administered in open-label conditions to all patients. The primary endpoint was the change from baseline of the Brief Pain Inventory Short Form item 5 to week 8. Secondary endpoints included the other Brief Pain Inventory Short Form items, and the assessment of anxiety, sleep, quality of life, patient's improvement, and safety.

RESULTS

One hundred and forty-one patients were included in the intention-to-treat population: 43 allocated to the TRZ30 group, 50 to the TRZ60 group, and 48 to the placebo group. After 8 weeks, the mean changes of Brief Pain Inventory Short Form item 5 from baseline were - 3.1, - 2.6, and - 2.5 in the TRZ30, TRZ60, and placebo groups, respectively. No statistically significant differences between groups were seen. Nevertheless, a better trend was observed for TRZ30 vs placebo (95% confidence interval - 1.30, 0.15; p = 0.1179), on top of the background effect of gabapentin administered to all study groups. 62.8% of patients achieved a ≥ 50% reduction in the TRZ30 group, 54% in the TRZ60 group, and 45.8% in the placebo group. At the same time, a statistically significant improvement was observed in Brief Pain Inventory Short Form item 6 for TRZ30 vs placebo (95% confidence interval - 1.54, - 0.07; p = 0.0314). No serious adverse event occurred during the trial and the most frequent treatment-emergent adverse events involved nervous system, QT prolongation, and gastrointestinal disorders.

CONCLUSIONS

All treatment groups showed a clinically meaningful pain improvement; nevertheless, patients in the TRZ30 treatment group reported better efficacy outcomes. This finding suggests that low doses of TRZ could be useful for treating painful diabetic neuropathy, and support further adequately powered confirmatory trials investigating the efficacy of TRZ.

CLINICAL TRIAL REGISTRATION

NCT03202979, date of registration: 29/06/2017.

Antidepressants for neuropathic pain

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 3, 2005 of The Cochrane Library. For many years antidepressant drugs have been used to manage neuropathic pain, and are often the first choice treatment. It is not clear, however, which antidepressant is more effective, what role the newer antidepressants can play in treating neuropathic pain, and what adverse effects are experienced by patients.

OBJECTIVES

To determine the analgesic effectiveness and safety of antidepressant drugs in neuropathic pain.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of antidepressants in neuropathic pain were identified in MEDLINE (1966 to Oct 2005); EMBASE (1980 to Oct 2005); the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, Issue 3, 2005; and the Cochrane Pain, Palliative and Supportive Care Trials Register (May 2002). Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators.

SELECTION CRITERIA

RCTs reporting the analgesic effects of antidepressant drugs in adult patients, with subjective assessment of pain of neuropathic origin. Studies that included patients with chronic headache and migraine were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors agreed the included studies, extracted data, and assessed methodological quality independently. Sixty one trials of 20 antidepressants were considered eligible (3293 participants) for inclusion. Relative Risk (RR) and Number-Needed-to-Treat (NNTs) were calculated from dichotomous data for effectiveness and adverse effects. This update includes 11 additional studies (778 participants).

MAIN RESULTS

Sixty one RCTs were included in total. Tricyclic antidepressants (TCAs) are effective and have an NNT of 3.6 (95% CI 3 to 4.5) RR 2.1 (95% CI 1.8 to 2.5) for the achievement of at least moderate pain relief. There is limited evidence for the effectiveness of the newer SSRIs but no studies of SNRIs were found. Venlafaxine (three studies) has an NNT of 3.1 (95% CI 2.2 to 5.1) RR 2.2 (95% CI 1.5 to 3.1). There were insufficient data to assess effectiveness for other antidepressants such as St Johns Wort and L-tryptophan. For diabetic neuropathy the NNT for effectiveness was 1.3 (95% CI 1.2 to 1.5) RR 12.4 (95% CI 5.2 to 29.2) (five studies); for postherpetic neuralgia 2.7 (95% CI 2 to 4.1), RR 2.2 (95% CI 1.6 to 3.1) (four studies). There was evidence that TCAs are not effective in HIV-related neuropathies. The number needed to harm (NNH) for major adverse effects defined as an event leading to withdrawal from a study was 28 (95% CI 17.6 to 68.9) for amitriptyline and 16.2 (95% CI 8 to 436) for venlafaxine. The NNH for minor adverse effects was 6 (95% CI 4.2 to 10.7) for amitriptyline and 9.6 (95% CI 3.5 to 13) for venlafaxine.

AUTHORS' CONCLUSIONS

This update has provided additional confirmation on the effectiveness of antidepressants for neuropathic pain and has provided new information on another antidepressant - venlafaxine. There is still limited evidence for the role of SSRIs. Whether antidepressants prevent the development of neuropathic pain (pre-emptive use) is still unclear. Both TCAs and venlafaxine have NNTs of approximately three. This means that for approximately every three patients with neuropathic pain who are treated with either of these antidepressants, one will get at least moderate pain relief. There is evidence to suggest that other antidepressants may be effective but numbers of participants are insufficient to calculate robust NNTs. SSRIs are generally better tolerated by patients and more high quality studies are required.

Prognostic ability of a good outcome to carpal tunnel release for decompression surgery in the lower extremity

For years, patients who were treated successfully with carpal tunnel release were told there was nothing that could be done about their lower extremity symptoms. Now that lower extremity nerve decompression has been accepted as an option to treat appropriate patients, the authors looked for correlations between a successful outcome with carpal tunnel syndrome and its predictive value of success for lower extremity nerve decompression. Data from a recent study demonstrate that a good result from upper extremity peripheral nerve surgery predicts the outcome for lower extremity peripheral nerve surgery in 88% of patients, and is, therefore, information valuable for prognosis and clinical decision-making.

Antidepressants for neuropathic pain

BACKGROUND

For many years antidepressant drugs have been used to manage neuropathic pain, and are often the first choice treatment. It is not clear, however, which antidepressant is more effective, what role the newer antidepressants can play in treating neuropathic pain, and what adverse effects are experienced by patients.

OBJECTIVES

To determine the analgesic effectiveness and safety of antidepressant drugs in neuropathic pain. Migraine and headache studies were not considered.

SEARCH STRATEGY

Randomised trials of antidepressants in neuropathic pain were identified in MEDLINE (1966 to Dec 2003); EMBASE (1980 to Dec 2003); the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library 2004, Issue 1; and the Cochrane Pain, Palliative and Supportive Care Trials Register (May 2002). Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators.

SELECTION CRITERIA

Randomised trials reporting the analgesic effects of antidepressant drugs in adult patients, with subjective assessment of pain of neuropathic origin. Studies that included patients with chronic headache and migraine were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers agreed the included studies, extracted data, and assessed methodological quality independently. Fifty trials of 19 antidepressants were considered eligible (2515 patients) for inclusion. Relative Risk (RR) estimates and Number-Needed-to-Treat (NNTs) were calculated from dichotomous data for effectiveness and adverse effects.

MAIN RESULTS

Tricyclic antidepressants (TCAs) are effective treatments for the treatment of neuropathic pain. Amitriptyline has an NNT of 2 (95%CI 1.7 to 2.5) RR 4.1(95%CI 2.9-5.9) for the achievement of at least moderate pain relief. There is limited evidence for the effectiveness of the newer selective serotonin reuptake inhibitor antidepressant drugs (SSRIs). There were insufficient data for an assessment of evidence of effectiveness for other antidepressants such as St Johns Wort, venlafaxine and L-tryptophan. For diabetic neuropathy the NNT for effectiveness was 1.3 (95%CI 1.2 to 1.5) RR 12.4(95%CI 5.2-29.2) (five studies); for postherpetic neuralgia 2.2 (95%CI 1.7 to 3.1), RR 4.8(95%CI 2.5-9.5)(three studies). There was evidence that TCAs are not effective in HIV-related neuropathies. The number needed to harm(NNH) for major adverse effects defined as an event leading to withdrawal from a study was 16 (95%CI: 10-45). The NNH for minor adverse effects was 4.6 (95%CI 3.3-6.7)

AUTHORS' CONCLUSIONS

Antidepressants are effective for a variety of neuropathic pains. The best evidence available is for amitriptyline. There are only limited data for the effectiveness of SSRIs. It is not possible to identify the most effective antidepressant until more studies of SSRIs are conducted.

Changing the Natural History of Diabetic Neuropathy: Incidence of Ulcer/Amputation in the Contralateral Limb of Patients With a Unilateral Nerve Decompression Procedure

The natural history of diabetes neuropathy is progressive and irreversible loss of sensibility in the feet, leading to ulceration and/or amputation in 15% of patients. The prevalence of neuropathy is more than 50% in those who have been diabetic for 20 years. Decompression of the tibial and peroneal nerves in those with diabetic neuropathy improves sensation in 70% of patients. The impact of this surgery on the development of ulcers and amputations in both the operated and the contralateral, nonoperated limb was evaluated in a retrospective analysis of 50 patients with diabetes a mean of 4.5 years (range, 2-7 years) from the date of surgery. No ulcers or amputations occurred in the index limb of these patients. In contrast, there were 12 ulcers and 3 amputations in 15 different patients in contralateral limbs. This difference was significant at P < 0.001. It is concluded that decompression of lower extremity nerves in diabetic neuropathy changes the natural history of this disease, representing a paradigm shift in health care costs.

Intracerebroventricular injection of trazodone produces 5-HT receptor subtype mediated anti-nociception at the supraspinal and spinal levels

Serotonin (5-HT) mediated anti-nociceptive effects induced by an anti-depressant, trazodone, are related to 5-HT(1A) receptor activities at the supraspinal level. 5-HT(3) receptor activation via the descending anti-nociceptive pathways may contribute to the trazodone mediated anti-nociception at the spinal level. Intracerebroventricular (i.c.v.) injection of trazodone dose-dependently impaired nociceptive responses in the formalin test in mice. Six and 15 microg of trazodone inhibited the early (P<0.05 or 0.01) and the late phases of the formalin test (P<0.05 or 0.01), while 3 microg had no effect. We examined the effects of a selective 5-HT(1A) receptor antagonist, WAY-100635, a single injection of which induced hyperalgesia (P<0.05), and blocked the anti-nociceptive effects of trazodone (P<0.01) when the two were simultaneously injected i.c.v. Intrathecal (i.t.) injection of a selective 5-HT(3) receptor antagonist, 3-tropanylindole-3-carboxylate hydrochloride, blocked the anti-nociceptive effects of i.c.v. trazodone (P<0.01), while WAY-100635 (i.t.) did not impair trazodone mediated anti-nociception. Trazodone mediated anti-nocicepton is related to serotonergic activity at both the supraspinal and the spinal level.

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.

Painful diabetic neuropathy

Chronic painful diabetic neuropathy causes symptoms that can last for many years and severely impair the quality of life of affected patients. This review describes the epidemiology, pathophysiology and treatment of chronic neuropathic pain. Particular emphasis is placed on a comprehensive review of the management of painful symptoms through a detailed review of the published literature using a variety of databases particularly Medline and EMBASE.

Painful diabetic neuropathy

Chronic painful diabetic neuropathy can cause a variety of challenges, particularly in successful treatment. The pain, which can last for years, can severely impair quality of life. Management is difficult, although the careful use of drugs can be significantly beneficial. Tricyclic and anticonvulsant drugs may be effective, with a variety of drugs available as second line agents. Newer non-drug systems such as electrical spinal cord stimulation represent exciting possibilities for the future management of this most difficult diabetic syndrome.

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

In the last 30 years antidepressant drugs have been used increasingly in the treatment of patients with chronic pain. This article reviews the results of some 40 placebo-controlled studies. It is difficult to make comparisons between the various studies because they often differ in terms of pain conditions, patient selection, antidepressant drug used, dosages, trial design, etc. However, in spite of this heterogeneity and other methodological problems it is clear that a wide range of pain conditions are responsive to antidepressant drug treatment, in particular: headache, migraine, facial pain, neurogenic pain, fibrositis, and probably arthritis and rheumatoid arthritis. More data need to be gathered in cancer pain, and in other conditions such as low back pain for which no, or very limited, effect has been shown. The beneficial effects of antidepressant drugs is in most cases of a mild to moderate degree, some time lag is necessary before it is completely manifest, and it tends to persist over time if drug treatment is continued in the long term. Strong evidence of efficacy is not evident for all the antidepressants, and there are probably significant differences in this respect between various drugs. The effect of a drug on pain does not seem necessarily to be related to its effect on mood. Further studies are needed to clarify this topic, and it will be necessary to examine specific pain conditions, compare different antidepressants, with reference to each other and to placebo, further investigate the role of drug plasma concentrations and control for the presence of concomitant psychiatric disturbances and for organic lesions responsible for the pain symptomatology.

Relief of diabetic neuropathy with fluoxetine

A 31-year-old woman with advanced diabetes mellitus with secondary autonomic and peripheral neuropathy was admitted for treatment of major depression. Previous therapy with desipramine resulted in exacerbation of the patient's orthostatic hypotension. After admission to the psychiatric facility she was initially stabilized medically and treated with psychotherapy. Subsequent treatment with low-dose fluoxetine 5 mg resulted in a decrease of the patient's diabetic neuropathy pain. Further increases in the fluoxetine dosage resulted in improvement of her depression and increased pain relief. Therapy with fluoxetine did not result in exacerbation of the orthostatic hypotension. This preliminary case report indicates that fluoxetine may be an alternative to the tricyclic antidepressants and trazodone in the treatment of diabetic peripheral neuropathy.

Depression and diabetic neuropathy: a complex relationship

In a group of 64 non-insulin-dependent diabetic females, a significant positive correlation between Zung self-rated depression scores and objective measurements of diabetic peripheral neuropathy was limited to those women with Zung scores greater than 50 (depressed group, n = 12). In the overall group, there was no significant linear or quadratic relationship between peripheral neuropathy and depression scores. The associations between depression, peripheral neuropathy, and diabetes are discussed.

Treatment of peripheral neuropathies

There are three general approaches to treatment of peripheral neuropathy. First, an attempt should be made to reverse the pathophysiological process if its nature can be elucidated. Second, nerve metabolism can be stimulated and regeneration encouraged. Third, even if the neuropathy itself cannot be improved, symptomatic therapy can be employed. This review outlines the options available for each approach.

Breaking the Cycle of Pain In Diabetic Peripheral Neuropathy

An attitude of helplessness pervades both patients and health professionals when dealing with the problems of dia betic peripheral neuropathy. Those afflicted are often over whelmed by the pain and find themselves unable to fulfill the daily requirements of their diabetes regimen. The in consistencies in amounts and timing of meals, levels of ac tivity, and scheduling of insulin injections can result in hyperglycemia, a state that has been found to correlate strongly with the occurrence of nerve damage. Thus the pain perpetrates itself. For the health professional, having to confront this devastating pain without objective factors to assess and few scientific treatment measures to offer con tributes to a sense of inadequacy and ignorance. It is fre quently assumed that "nothing can be done." In reality, health professionals do have something to offer the person suffering from this condition. First, they can provide infor mation about the relationship between control and compli cations, and explain the need for the patient to change those behaviors that may be perpetuating the pain. Sec ond, and most importantly, health professionals can con vey support and confidence, without which many patients will be unable to make the changes in their behavior neces sary to resolve their pain.