Combining norepinephrine and serotonin reuptake inhibition mechanisms for treatment of depression: a double-blind, randomized study

SNRIs: their pharmacology, clinical efficacy, and tolerability in comparison with other classes of antidepressants

The class of serotonin and norepinephrine reuptake inhibitors (SNRIs) now comprises three medications: venlafaxine, milnacipran, and duloxetine. These drugs block the reuptake of both serotonin (5-HT) and norepinephrine with differing selectivity. Whereas milnacipran blocks 5-HT and norepinephrine reuptake with equal affinity, duloxetine has a 10-fold selectivity for 5-HT and venlafaxine a 30-fold selectivity for 5-HT. All three SNRIs are efficacious in treating a variety of anxiety disorders. There is no evidence for major differences between SNRIs and SSRIs in their efficacy in treating anxiety disorders. In contrast to SSRIs, which are generally ineffective in treating chronic pain, all three SNRIs seem to be helpful in relieving chronic pain associated with and independent of depression. Tolerability of an SNRI at therapeutic doses varies within the class. Although no direct comparative data are available, venlafaxine seems to be the least well-tolerated, combining serotonergic adverse effects (nausea, sexual dysfunction, withdrawal problems) with a dose-dependent cardiovascular phenomenon, principally hypertension. Duloxetine and milnacipran appear better tolerated and essentially devoid of cardiovascular toxicity.

Are there differences in the symptoms that respond to a selective serotonin or norepinephrine reuptake inhibitor?

BACKGROUND

We examined two previously published studies comparing a norepinephrine (NE) selective agent, reboxetine, and a serotonin (5-HT) selective agent, fluoxetine, to determine if these agents have different effects on individual depressive symptoms.

METHODS

Both studies were 8-week, double-blind, comparison studies of men and women with DSM III-R major depression. Within-group effect sizes for individual symptom change on the Hamilton Depression Rating Scale (HAMD) were determined in the observed case samples and in patients for whom the symptom was relatively severe at baseline. We required that any significant differences in one sample be cross-validated in the second.

RESULTS

Two hundred fifty-three subjects in study I and 168 subjects in study II were randomized to reboxetine or fluoxetine. In both samples, depressed mood, decreased interest, and psychic anxiety had the greatest change. Effect sizes for all HAMD symptoms were similar for the two drugs. No difference between groups in one sample was replicated in the second. Among subjects with severe symptoms, no significant differences were cross-validated.

CONCLUSIONS

Reboxetine and fluoxetine appear to have similar effects on depressive symptoms. These data suggest that NE and 5-HT selective antidepressant drugs act through the same final common pathway and challenge the belief that symptom differences are useful for antidepressant selection.

Duloxetine: A Dual Serotonin-Norepinephrine Reuptake Inhibitor for Treatment of Major Depressive Disorder

The burden of mental illness has been underestimated worldwide. Depression was the fourth leading cause of disease burden in the world in 1990 and is projected to be the second leading cause of disability by 2020. It is a leading cause of morbidity and mortality in the United States, costing billions of dollars annually in direct and indirect medical costs and losses in productivity. Patients with major depressive disorder (MDD) may experience both psychological and medical complaints, including somatic sensations or pain. Some antidepressants have been shown to treat chronic pain syndromes, but despite the variety of antidepressants available in the United States, only 65-70% of patients respond to initial antidepressant treatment. Treatments are limited by delayed onset of antidepressant effects, side effects, partial response, and treatment resistance. Duloxetine, approved by the U.S. Food and Drug Administration for the treatment of MDD, is a reuptake inhibitor at serotonergic and noradrenergic neurons and appears to have low affinity for other neurotransmitter systems. In clinical trials, duloxetine was effective for the treatment of MDD and was well tolerated. Further study is needed to compare its efficacy with that of other antidepressants, to clarify effects on somatic symptoms, and to assess potential adverse cardiovascular and sexual side effects. Duloxetine is also approved for the management of diabetic peripheral neuropathic pain and is under investigation for the treatment of stress urinary incontinence in women.

Paroxetine combined with a 5-HT(1A) receptor antagonist reversed reward deficits observed during amphetamine withdrawal in rats

RATIONALE

"Diminished interest or pleasure" in rewarding stimuli is an affective symptom of amphetamine withdrawal and a core symptom of depression. An operational measure of this symptom is elevation of brain stimulation reward thresholds during drug withdrawal. Data indicated that increasing serotonin neurotransmission by co-administration of the selective serotonin reuptake inhibitor (SSRI) fluoxetine and the serotonin-1A receptor antagonist p-MPPI reversed reward deficits observed during drug withdrawal (Harrison et al. 2001).

OBJECTIVES

We tested the hypothesis that increased serotonergic and noradrenergic neurotransmission, using the SSRI paroxetine which also inhibits noradrenaline reuptake, would alleviate affective aspects of amphetamine withdrawal.

METHODS

A discrete-trial, current-threshold, self-stimulation procedure was used to assess brain reward function. The effects of paroxetine and p-MPPI alone and in combination were assessed in non-drug-withdrawing animals. We assessed also the effects of paroxetine and p-MPPI alone and in combination on reward deficits associated with amphetamine withdrawal.

RESULTS

Paroxetine or p-MPPI alone had no effect on thresholds, while the co-administration of p-MPPI (3 mg/kg) and paroxetine (1.25 mg/kg) elevated thresholds in non-withdrawing rats. Amphetamine withdrawal resulted in threshold elevations. The co-administration of p-MPPI and paroxetine reduced the duration of amphetamine-withdrawal-induced reward deficits.

CONCLUSIONS

Increased serotonergic and noradrenergic neurotransmission decreased reward function in non-withdrawing rats, while the same treatment reversed reward deficits associated with amphetamine withdrawal. Considering that paroxetine acts on both the serotonin and noradrenaline transporter, these results indicate that the affective symptoms of amphetamine withdrawal, similar to non-drug-induced depressions, may be, in part, mediated through reduced serotonergic and noradrenergic neurotransmission.

Therapeutic alternatives for difficult-to-treat depression: a narrative review of the state of the evidence

Despite the large number of depressed patients who do not respond to first-line antidepressants, the evidence base of alternate strategies is quite thin. In this article, a simple 5-stage system for categorizing treatment-resistant depression (TRD) is described and the evidence pertaining to the major strategies currently utilized is summarized using four grades, ranging from D (case reports only) to A (multiple positive placebo-controlled trials). It is concluded that the level of evidence supporting many of the contemporary strategies used for TRD (eg, combinations of antidepressants and augmentation with medications such as pindolol, buspirone, or modafinil) is scanty at best. Even the fundamental question concerning "to augment or to switch" is not answerable with available data. It is noted that the best-documented treatments (ie, lithium augmentation, switching to a monoamine oxidase inhibitor, and electroconvulsive therapy) are among the least utilized. This state of affairs will improve with completion of the studies of Systematic Treatment Alternatives to Relieve Depression, a large multicenter study of difficult-to-treat depression funded by the National Institute of Mental Health. There is a need for greater collaboration among academicians and organizations, such as the American Psychiatric Association, the National Institute of Mental Health, and the pharmaceutical industry, to ensure that sufficient research is conducted so that clinician's choices for patients with TRD can be guided by empirical evidence.

New trends in the treatment of anxiety disorders

Anxiety disorders are among the most prevalent psychiatric disorders in the general population, found nearly twice as often in women, and estimated to affect 26.9 million individuals in the United States alone. Anxiety disorders are associated with considerable chronicity, morbidity, and disability. Treatment of anxiety disorders includes pharmacologic and nonpharmacologic approaches. The first-line pharmacologic treatments currently include the use of serotonin reuptake inhibitors and selective serotonin reuptake inhibitors. However, despite the general success of the available treatments, no single anxiolytic appears to be effective for all patients suffering from anxiety. Low recovery rates have been reported in all anxiety disorders, underscoring the need for optimizing treatment for these disabling disorders. In recent years, there is increasing interest in the use of atypical neuroleptics in the treatment of anxiety disorders patients. This article discusses the emerging data on the use of these agents in the treatment of anxiety with a focus on treatment-refractory patients and on the implications for the treatment of women suffering from anxiety disorders.