Deuterium-labelled p-tyramine challenge test and phenolsulfotransferase activity in depressed patients--failure to replicate decreased p-tyramine conjugation in depression

Fluvoxamine versus other anti-depressive agents for depression

BACKGROUND

Fluvoxamine, one of the oldest selective serotonin reuptake inhibitors (SSRIs), is prescribed to patients with major depression in many countries. Several studies have previously reviewed the efficacy and tolerability of fluvoxamine for the treatment of major depression. However, these reviews are now outdated.

OBJECTIVES

Our objective is to evaluate the effectiveness, tolerability and side effect profile of fluvoxamine for major depression in comparison with other anti-depressive agents, including tricyclics (TCAs), heterocyclics, other SSRIs, SNRIs, other newer agents and other conventional psychotropic drugs.

SEARCH STRATEGY

We searched the Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Register. Trial databases and ongoing trial registers in North America, Europe, Japan and Australia, were handsearched for randomised controlled trials. We checked reference lists of the articles included in the review, previous systematic reviews and major textbooks of affective disorder for published reports and citations of unpublished research. The date of last search was 31 August 2008.

SELECTION CRITERIA

We included all randomised controlled trials, published in any language, that compared fluvoxamine with any other active antidepressants in the acute phase treatment of major depression.

DATA COLLECTION AND ANALYSIS

Two independent review authors inspected citations and abstracts, obtained papers, extracted data and assessed the risk of bias of included studies. We analysed dichotomous data using odds ratios (ORs) and continuous data using the standardised mean difference (SMD). A random effects model was used to combine studies.

MAIN RESULTS

A total of 54 randomised controlled trials (n = 5122) were included. No strong evidence was found to indicate that fluvoxamine was either superior or inferior to other antidepressants regarding response, remission and tolerability. However, differing side effect profiles were evident, especially with regard to gastrointestinal side effects of fluvoxamine when compared to other antidepressants. For example, fluvoxamine was generally associated with a higher incidence of vomiting/nausea (versus imipramine, OR 2.23, CI 1.59 to 3.14; versus clomipramine, OR 2.13, CI 1.06 to 4.27; versus amitriptyline, OR 2.86, CI 1.31 to 2.63).

AUTHORS' CONCLUSIONS

We found no strong evidence that fluvoxamine was either superior or inferior to any other antidepressants in terms of efficacy and tolerability in the acute phase treatment of depression. However, differing side effect profiles were evident. Based on these findings, we conclude that clinicians should focus on practical or clinically relevant considerations, including these differences in side effect profiles.

Detoxified alcoholics, major depressives and tyramine sulphate excretion

The excretion of tyramine sulphate after challenge with an oral load of tyramine was assessed in recently detoxified, clinically depressed alcoholics and a matched group of major depressives. Tyramine excretion in the alcohol group (mean 5.95 ± 3.28 mg/3 h SD) was in the range previously observed in controls and was significantly higher than in the matched depressives (mean 3.43 ± 2.37 mg/3 h SD). Tyramine sulphate excretion has been suggested as a genetic vulnerability marker for major depression. This study suggests that depression associated with alcohol withdrawal is not characterised by decreased tyramine sulphate excretion after oral tyramine challenge, such decreased conjugation only being present, perhaps, in those patients with pre- existing endogenous depressive vulnerability. Although a genetic link between alcoholism and depression exists, these results support the absence of such a link to major depression.

The trace amines and their acidic metabolites in depression--an overview

1. Investigations of the role of the trace amines (phenylethylamine, tryptamine, m- and p-tyramine) and their acidic metabolites (phenylacetic, indoleacetic, m- and p-hydroxyphenylacetic acids) in depression are reviewed. 2. The evidence for the phenylethylamine hypothesis of depression is mixed. 3. Reduced phenylacetic acid levels in urine, plasma and CSF and changes in those levels during treatment with antidepressants show potential as state markers for depression. 4. Impaired p-tyramine conjugation following a tyramine challenge may be a good trait marker for depression.

The 'cerebral diabetes' paradigm for unipolar depression

Unipolar depression, alcoholism and suicide have become more common over the past decades. Genetic studies have attempted to link (bipolar) affective disorder to the short arm of chromosome 11 (where the loci for insulin, insulin growth factor (IGF), tyrosine hydroxylase (TH) and h-ras-oncogene are located) but these have failed. Since TH and the insulin receptor require phosphorylation by protein kinases, then a defect of the h-ras-oncogene or its products (p21) could disorder both these systems and compromise catecholaminergic transmission in neurones and energy flow in glial cells. This could lead not only to a predisposition to depression ('trait markers') but to neurotoxic damage, predisposed by inadequate cytosol Mg2+ levels of hypometabolism. Tyrosine, tryptophan and phenylalanine hydroxylases all require tetrahydrobiopterin (BH4) which allosterically regulates its own activity as well as that of these enzymes. Anything which impairs this cofactor could lead to overt depression in predisposed individuals, and the heterocyclic amines are being increasingly implicated. These substances are derived from fried and broiled meats, azo food dyes, soft drinks and hard candies, but particularly from cigarette and petroleum fumes. The heterocyclic amines can inhibit aromatic-l-amino-acid-decarboxylase (AADC) as well as the hydroxylases reversibly, but BH4 is inhibited noncompetitively. Thus, susceptible individuals (those with inherited defective protein kinase phosphorylation) might be 'tipped over' by chronic exposure to these neurotoxins. The rising incidence of unipolar depression-associated morbidity could be significantly linked to increasing levels of heterocyclic amines in the developed nations.