Antidepressant augmentation and combinations

Vagus Nerve Stimulation (VNS) and Other Augmentation Strategies for Therapy-Resistant Depression (TRD): Review of the Evidence and Clinical Advice for Use

In addition to electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS), vagus nerve stimulation (VNS) is one of the approved neurostimulation tools for treatment of major depression. VNS is particularly used in therapy-resistant depression (TRD) and exhibits antidepressive and augmentative effects. In long-term treatment, up to two-thirds of patients respond. This mini-review provides a comprehensive overview of augmentation pharmacotherapy and neurostimulation-based treatment strategies, with a special focus on VNS in TRD, and provides practical clinical advice for how to select TRD patients for add-on neurostimulation treatment strategies.

Algorithm-guided treatment versus treatment as usual for major depression

AIMS

The remission rates for patients with major depressive disorder (MDD) during algorithm-guided treatment (AGT), which consisted of four treatment strategy steps were prospectively compared with treatment as usual (TAU).

METHODS

The remission rates of patients with mild or moderate MDD during AGT (n = 83) were compared with TAU (n = 127).

RESULTS

The remission rate in the AGT group (60.2%) was approximately 10% greater than that in the TAU group (49.7%). The median number of days to achieve remission in the AGT group (93 days) was half as long as that in the TAU group (191 days). The hazard ratio of remission was 1.5 (95% confidence interval: = 1.2-1.8). A higher rate of lithium augmentation in the AGT group (20.5%) compared to the TAU (4.7%) may have led to the greater remission rate. Most participants who did not achieve remission either during the initial or second treatment steps dropped out from AGT.

CONCLUSIONS

AGT may be superior to TAU for patients with mild or moderate MDD, based on the remission rates achieved. The later treatment steps in the AGT, however, were rarely utilized because participants who did not receive any benefit dropped out early.

Thyrotropin-releasing hormone (TRH) in the cerebellum

Thyrotropin-releasing hormone (TRH) was originally isolated from the hypothalamus. Besides controlling the secretion of TSH from the anterior pituitary, this tripeptide is widely distributed in the central nervous system and regarded as a neurotransmitter or modulator of neuronal activities in extrahypothalamic regions, including the cerebellum. TRH has an important role in the regulation of energy homeostasis, feeding behavior, thermogenesis, and autonomic regulation. TRH controls energy homeostasis mainly through its hypophysiotropic actions to regulate circulating thyroid hormone levels. Recent investigations have revealed that TRH production is regulated directly at the transcriptional level by leptin, one of the adipocytokines that plays a critical role in feeding and energy expenditure. The improvement of ataxic gait is one of the important pharmacological properties of TRH. In the cerebellum, cyclic GMP has been shown to be involved in the effects of TRH. TRH knockout mice show characteristic phenotypes of tertiary hypothyroidism, but no morphological changes in their cerebellum. Further analysis of TRH-deficient mice revealed that the expression of PFTAIRE protein kinase1 (PFTK1), a cdc2-related kinase, in the cerebellum was induced by TRH through the NO-cGMP pathway. The antiataxic effect of TRH and TRH analogs has been investigated in rolling mouse Nagoya (RMN) or 3-acetylpyridine treated rats, which are regarded as a model of human cerebellar degenerative disease. TRH and TRH analogs are promising clinical therapeutic agents for inducing arousal effects, amelioration of mental depression, and improvement of cerebellar ataxia.

Peripheral thyroid dysfunction in depression

The involvement of the thyroid gland and thyroid hormones is generally believed to be important in the aetiopathogenesis of major depression. Major support comes from studies in which alterations in components of the hypothalamic-pituitary-thyroid (HPT) axis have been documented in patients with primary depression. However, screening thyroid tests are often routine and add little to the diagnostic evaluation. Overt thyroid disease is rare among depressed inpatients. The finding that depression often co-exists with autoimmune subclinical thyroiditis suggests that depression may cause alterations in the immune system, or that in fact it could be an autoimmune disorder itself. The outcome of treatment and the course of depression may be related to thyroid status as well. Augmentation of antidepressant therapy with the co-administration of thyroid hormones (mainly T3) is a well-documented treatment option for refractory depressed patients. Review of the literature suggests that there are no conclusive data on the role of thyroid function in depression. It is clear that depression is not characterised by an overt thyroid dysfunction, but it is also clear that a subgroup of depressed patients may manifest subtle thyroid abnormalities, or an activation of an autoimmune process. There is a strong possibility that the presence of a subtle thyroid dysfunction is a negative prognostic factor for depression and may demand specific therapeutic intervention.

Antidepressant combinations: epidemiological considerations

OBJECTIVE

To evaluate the treatment options in patients who do not respond appropriately to a single antidepressant alone.

METHOD

The medical literature was reviewed.

RESULTS

A number of strategies are available if a patient fails to respond adequately to initial antidepressant treatment, including the combination with another psychoactive drug. Evidence published to date appears to suggest that benzodiazepines are the drugs most frequently combined with antidepressants. The combination of two antidepressants together is less common, occurring in approximately 5-15% of cases showing a poor initial response. The key figures involved in such co-prescription are psychiatrists.

CONCLUSION

There appears to be considerable variability in the data concerning combined prescription of antidepressants, with differences arising depending on the type of physician, the type of patient or illness and the geographical area. It is also unclear how closely research findings parallel with what doctors do in everyday practice.

Mydriasis, Hypertension, and Tachycardia Possibly Associated with Venlafaxine Augmentation of Mirtazapine

Objective:

To report a case of mydriasis and hypertension resulting from concomitant use of mirtazapine and venlafaxine.

Case Summary:

A 36-year-old man had been treated for 7 weeks with mirtazapine up to 60 mg/day without satisfactory therapeutic effects. Venlafaxine extended-release up to 150 mg/day was added with the aim to boost the antidepressant effect. After 5 days of venlafaxine treatment, the patient developed apparent mydriasis, and after 9 days of therapy, the patient's blood pressure peaked at 200/120 mm Hg. While he remained under mirtazapine therapy, both symptoms resolved within 24 hours after venlafaxine discontinuation.

Discussion:

A rise in blood pressure is a well-known phenomenon with venlafaxine. As of September 27, 2004, this is the first case of hypertension after venlafaxine augmentation of mirtazapine and the first case to report a preceding mydriasis. We propose an excess of noradrenergic activity due to the combination of venlafaxine and mirtazapine to be the most probable cause.

Conclusions:

Whereas the mirtazapine/venlafaxine combination seems a promising approach in the treatment of refractory depression, this strategy may be associated with adverse drug events not observed with either of the drugs when given alone. Mydriasis may be a good premonitory sign for hypertension.

Nitric oxide synthase inhibitors augment the effects of serotonin re-uptake inhibitors in the forced swimming test

The problem of antidepressant-resistant depression has necessitated finding ways of augmenting the actions of currently existing antidepressants. The present studies investigate the possibility of synergistic interactions between nitric oxide (NO) synthase inhibitors and antidepressants in the mouse forced swim test (FST), a pre-clinical test of antidepressant activity. Treatment with a behaviourally subactive dose of the NO synthase inhibitor NG-nitro-L-arginine (L-NA) (3 mg/kg) augmented the behavioural effect of the tricyclic antidepressant imipramine. In a similar fashion L-NA (3 mg/kg) augmented the effect of the selective serotonin re-uptake inhibitor (SSRI) fluoxetine but not the noradrenaline re-uptake inhibitor, reboxetine in the FST. The interaction observed between L-NA and fluoxetine generalised to other selective serotonin re-uptake inhibitors, namely, sertraline and citalopram in the FST. Treatment with a subactive dose of the neuronally selective NO synthase inhibitor, 7-nitroindazole (30 and 50 mg/kg), augmented the behavioural effects of imipramine and fluoxetine, respectively. Thus inhibition of NO synthase enhances the activity of antidepressants that work via a serotonergic mechanism in the FST. The results of the present investigation support a view that antidepressant effects, or enhancement of such effects in the FST, may be elicited via NO synthase inhibition. Furthermore, these data raise the possibility that inhibition of NO synthase could be used as a strategy to enhance the clinical efficacy of serotonergic antidepressants.

Valproate modulates TRH receptor, TRH and TRH-like peptide levels in rat brain

We have tested our hypothesis that alterations in the levels of TRH receptors, and the synthesis and release of tripeptide TRH, and other neurotropic TRH-like peptides mediate some of the mood stabilizing effects of valproate (Valp). We have directly compared the effect of 1 week of feeding two major mood stabilizers, Valp and lithium chloride (LiCl) on TRH binding in limbic and extra-limbic regions of male WKY rats. Valp increased TRH receptor levels in nucleus accumbens and frontal cortex. Li increased TRH receptor binding in amygdala, posterior cortex and cerebellum. The acute, chronic and withdrawal effects of Valp on brain levels of TRH (pGlu-His-Pro-NH2, His-TRH) and five other TRH-like peptides, Glu-TRH, Val-TRH, Tyr-TRH, Leu-TRH and Phe-TRH were measured by combined HPLC and RIA. Acute treatment increased TRH and TRH-like peptide levels within most brain regions, most strikingly in pyriform cortex. The fold increases (in parentheses) were: Val-TRH (58), Phe-TRH (54), Tyr-TRH (25), TRH (9), Glu-TRH (4) and Leu-TRH (3). We conclude that the mood stabilizing effects of Valp may be due, at least in part, to its ability to alter TRH and TRH-like peptide, and TRH receptor levels in the limbic system and other brain regions implicated in mood regulation and behavior.

Treatments for depression: wisdom imparted from treatments discarded

Many different forms of treatment have been used with patients suffering from depression. It can be difficult to examine current treatments and anticipate problems, mistakes, and limitations. However, a historical perspective allows an appreciation of the strengths and limitations of older treatments, and sheds light on current strategies. A variety of effective treatments have been discarded and forgotten. Important lessons can be learned by reviewing the history of treatments for depression. Many treatment strategies were based on accidental discovery, but nonetheless were found effective in reducing the symptoms of depression. Both case examples and group studies have documented the effectiveness of these older treatments. A review of discarded treatments reveals how a biological model can be limited in its ability to produce a lasting cure. Caution and skepticism are encouraged when innovative treatments are proposed.

Amantadine as augmentation therapy in the management of treatment-resistant depression

Treatment-resistant depression is an important clinical problem presenting a major challenge to clinical psychiatry. While several strategies have been attempted, including medication switch, antidepressant polypharmacy and various augmentative regimens, success remains limited. Amantadine (AMN), an agent traditionally used in the treatment and prophylaxis of influenza, is now known to exhibit prominent effects at the level of dopaminergic, monoamine oxidase and N-methyl-D-aspartate systems. The present reports on the efficacy of AMN as augmentation to standard antidepressant treatment in patients with treatment-resistant depression. Eight patients with treatment-resistant depression consented to receive AMN, titrated up to a dose of 300 mg, over a period of 4 weeks in a non-blinded fashion. Improvement in both depression and anxiety scores were observed from week 1, with patients exhibiting improvement of depressive scores of up to 49% by study completion. Females appeared to exhibit a stronger response, and within a shorter period of time. Side-effects reported included dry mouth and sedation. AMN appears to demonstrate efficacy as a safe and effective augmentative agent in treatment-resistant depression. Further studies are clearly mandated to test these preliminary observations in a double-blinded manner.

Lithium modulates expression of TRH receptors and TRH-related peptides in rat brain

Lithium is an established mood stabilizer and neuroprotective agent frequently used in the treatment of bipolar disorder and as an adjuvant in drug-resistant unipolar depression. The mechanisms underlying both the therapeutic efficacy of lithium and the exacerbation of symptoms following rapid withdrawal are not understood. From previous studies showing antidepressant and neuroprotective activities of thyrotropin releasing hormone (TRH) and TRH-related neuropeptides we hypothesized that lithium may have substantial effects on the expression and secretion of these peptides and/or their receptors in various rat brain regions involved in the regulation of mood. Chronic lithium effect on TRH receptor binding studies: The effect of 1 and 2 weeks of dietary lithium on [(3)H]3-Me-His-TRH binding to plasma membranes of nucleus accumbens, amygdala and pituitary of young adult male Wistar and the endogenously 'depressed' Wistar Kyoto (WKY) rats was measured by the method of Burt and Taylor [Burt, D.R., Taylor, R.L., Endocrinology 106 (1980) 1416-1423]. Acute, chronic and withdrawal effect of lithium on TRH and TRH-like peptide levels in young, adult male Sprague-Dawley rats: Rats were divided into four lithium treatment groups. Control animals received a standard laboratory rodent chow. The acute group received a single i.p. injection of 1.5 milli-equivalents of LiCl 2 h prior to killing. The chronic and withdrawal groups received standard rodent chow containing 1.7 g/kg LiCl for 2 weeks. Withdrawal rats were returned to standard chow 48 h prior to killing while the chronic animals continued on the LiCl diet. TRH, TRH-Gly (pGlu-His-Pro-Gly, a TRH precursor), EEP (pGlu-Glu-Pro-NH(2), a TRH-like peptide with antidepressant activity) and Ps4 (a prepro-TRH-derived TRH-enhancing decapeptide) immunoreactivity (IR) were measured in 13 brain regions. The remaining samples were pooled and fractionated by high-pressure liquid chromatography followed by EEP radioimmunoassay. Chronic lithium treatment increased [(3)H]3Me-TRH binding in the nucleus accumbens and amygdala about two-fold in both Wistar and WKY rats but no change was observed in pituitary binding. The most widespread changes in TRH and TRH-related peptide levels were observed in the withdrawal group compared to the controls. The direction of change for the total IR was consistent for all TRH-IR and TRH-related peptide-IR within a given tissue. For example, withdrawal increased all peptide levels in the pyriform cortex and striatum but decreased these levels in the anterior cingulate and lateral cerebellum. Both acute injection and chronic treatment with LiCl decreased TRH and TRH-related peptide levels in the entorhinal cortex. Acute injection and withdrawal both increased EEP-IR in striatum by more than two-fold. The acute effects are most likely due to changes in the release of these peptides since 2 h is not sufficient time for alterations in peptide biosynthesis. Chronic treatment increased levels of pGlu-Phe-Pro-NH(2) levels in hippocampus, pGlu-Leu-Pro-NH(2), and peak '2' in septum by more than four-fold. The present results are consistent with a component role for TRH and related peptides in the mood-altering effects of lithium administration and withdrawal frequently observed during treatment for depression and bipolar disorder.

Dysphoric mania induced by high-dose mirtazapine: a case for 'norepinephrine syndrome'?

The antidepressant mirtazapine antagonizes central presynaptic alpha2-adrenergic auto- and heteroreceptors resulting in increased central norepinephrine and serotonin activity. Histamine H2 receptors are also antagonized, as are postsynaptic serotonin 5-HT2 and 5-HT3 receptors, leading to serotonergic activity primarily via 5-HT1A receptors. Based on the case report of a patient who developed mania with higher than recommended dosage of mirtazapine, we review the literature on the atypical nature of manic symptoms with mirtazapine. Eight subjects, including those in our study, were identified as having developed mirtazapine-induced mania with atypical features, consisting of dysphoria, irritability, insomnia, psychomotor agitation and abnormal gait. Predisposing features may have included the presence of underlying brain dysfunction and certain selective serotonin reuptake inhibitor-mirtazapine combinations. Dysphoric mania with atypical features may be induced by mirtazapine, providing support for a common hypothesis such as 'central norepinephrine hyperactivity' as the basis for development of mania with mirtazapine.

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.