Relationship between response to phenelzine and MAO inhibition in a clinical trial of phenelzine, amitriptyline and placebo

Monoamine Oxidase Inhibitors (MAOIs) in Psychiatric Practice: How to Use them Safely and Effectively

Monoamine oxidase inhibitors (MAOIs) were among the first licensed pharmacological treatments for patients with depression but over time have fallen out of mainstream clinical use. This has led to a loss of clinician training opportunities and reduced availability of MAOIs for prescribing. This article provides a concise and practical overview of how to use MAOIs safely and effectively in psychiatric practice. We consider the history of MAOIs, why they are not used more frequently, their mechanisms of action, availability, indications and efficacy, general tolerability, withdrawal symptoms, and safety considerations (including hypertensive reactions and serotonin syndrome). Practical advice is given in terms of dietary restrictions, interactions with other medications (both prescribed and non-prescribed), and how prescribers can stop and switch MAOIs, both within the drug class and outside of it. We also provide advice on choice of MAOI and treatment sequencing. Lastly, we consider emerging directions and potential additional indications.

Amitriptyline versus placebo for major depressive disorder

BACKGROUND

Amitriptyline is a tricyclic antidepressant that was synthesised in 1960 and introduced as early as 1961 in the USA, but is still regularly used. It has also been frequently used as an active comparator in trials on newer antidepressants and can therefore be called a 'benchmark' antidepressant. However, its efficacy and safety compared to placebo in the treatment of major depression has not been assessed in a systematic review and meta-analysis.

OBJECTIVES

To assess the effects of amitriptyline compared to placebo or no treatment for major depressive disorder in adults.

SEARCH METHODS

We searched the Cochrane Depression, Anxiety and Neurosis Group's Specialised Register (CCDANCTR-Studies and CCDANCTR-References) to August 2012. This register contains relevant randomised controlled trials from: The Cochrane Library (all years), EMBASE (1974 to date), MEDLINE (1950 to date) and PsycINFO (1967 to date). The reference lists of reports of all included studies were screened and manufacturers of amitriptyline contacted for details of additional studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs) comparing amitriptyline with placebo or no treatment in patients with major depressive disorder as diagnosed by operationalised criteria.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. For dichotomous data, we calculated the odds ratio (OR) with 95% confidence intervals (CI). We analysed continuous data using standardised mean differences (with 95% CI). We used a random-effects model throughout.

MAIN RESULTS

The review includes 39 trials with a total of 3509 participants. Study duration ranged between three and 12 weeks. Amitriptyline was significantly more effective than placebo in achieving acute response (18 RCTs, n = 1987, OR 2.67, 95% CI 2.21 to 3.23). Significantly fewer participants allocated to amitriptyline than to placebo withdrew from trials due to inefficacy of treatment (19 RCTs, n = 2017, OR 0.20, 95% CI 0.14 to 0.28), but more amitriptyline-treated participants withdrew due to side effects (19 RCTs, n = 2174, OR 4.15, 95% CI 2.71 to 6.35). Amitriptyline also caused more anticholinergic side effects, tachycardia, dizziness, nervousness, sedation, tremor, dyspepsia, sedation, sexual dysfunction and weight gain. In subgroup and meta-regression analyses the results of the primary outcome were robust towards publication year (1971 to 1997), mean participant age at baseline, mean amitriptyline dose, study duration in weeks, pharmaceutical sponsor, inpatient versus outpatient setting and two-arm versus three-arm design. However, higher severity at baseline was associated with higher superiority of amitriptyline (P = 0.02), while higher responder rates in the placebo groups were associated with lower superiority of amitriptyline (P = 0.05). The results of the primary outcome were rather homogeneous, reflecting comparability of the trials. However, methods of randomisation, allocation concealment and blinding were usually poorly reported. Not all studies used intention-to-treat analyses and in many of them standard deviations were not reported and often had to be imputed. Funnel plots suggested a possible publication bias, but the trim and fill method did not change the overall effect size much (seven adjusted studies, OR 2.64, 95% CI 2.24 to 3.10).

AUTHORS' CONCLUSIONS

Amitriptyline is an efficacious antidepressant drug. It is, however, also associated with a number of side effects. Degree of placebo response and severity of depression at baseline may moderate drug-placebo efficacy differences.

The role of monoamine oxidase inhibitors in current psychiatric practice

The use of monoamine oxidase inhibitors (MAOIs) by psychiatrists has declined over the past several decades with the expansion of psychiatrists' pharmacologic armamentarium. This trend has also been driven by concern about food and drug interactions and side effects, as well as waning physician experience with these medications. Many psychiatrists, in fact, never prescribe MAOIs. Recent research has liberalized the MAOI diet and identified symptom presentations more likely to respond to these medications. Thus, clinicians must continue to familiarize themselves with the properties of and indications for prescribing MAOIs.

Meta-Analysis of Placebo Rates in Major Depressive Disorder Trials

BACKGROUND

Placebo effects in major depressive disorder (MDD) have received much interest in the medical literature. However, few quantitative analyses have been done in homogeneous populations.

OBJECTIVE

To determine efficacy rates for placebo in patients with MDD; to quantify the correlation between efficacy and publication year, as well as between placebo and drug response rates.

DESIGN

Searching MEDLINE (1966-December 2000), EMBASE (1998-February 2001), HealthSTAR (1975-December 2000), and Cochrane (1980-December 2000) databases, randomized, placebo-controlled trials were retrieved including patients with MDD as defined by Diagnostic and Statistical Manual of Mental Disorders, 3rd and 4th editions criteria, Hamilton Rating Scale for Depression score >/=18 or Montgomery-Asberg Depression Rating Scale score >/=16, reporting successes as 50% decreases in scores after 6-8 weeks of treatment. Response rates were summarized using a random effects meta-analysis for per protocol (PP) and intent-to-treat (ITT) results.

RESULTS

We included 24 of 134 potential studies examining 4459 patients, 1786 on placebo and 2673 on an antidepressant. Placebo response rates were 45.5% (PP) and 26.9% (ITT). Correlations were significant between year and rates (PP rho 0.448, p = 0.042; ITT rho 0.557; p = 0.006), but not for active drugs. Placebo and drug rates were correlated (PP r 0.397, p = 0.020; ITT r 0.539; p = 0.002).

CONCLUSIONS

These placebo rates confirm those reported previously, but were from a homogeneous population. Although statistically significant, the correlation between drug and placebo rates was lower than others reported. During the study period, placebo rates increased linearly; active drugs did not. Correlations between placebo and drug response rates reflected moderate to strong effect sizes. We suggest that current methodology has been unsuccessful in achieving unbiased double-blind conditions not influenced by extra-trial factors, including time.

Evidence-based data on pain relief with antidepressants

This structured review addresses the issue of whether antidepressants have an antinociceptive (analgesic) effect for chronic pain independent of their antidepressant effect. In order to answer this question, human acute pain studies, individual placebo-controlled studies for the treatment of specific chronic pain syndromes, and metaanalytic studies were reviewed and placed into table format. Analysis of this evidence led to the following conclusions: The evidence was consistent in indicating that overall antidepressants may have an antinociceptive effect in chronic pain, and that these drugs were effective for neuropathic pain. There was also some evidence that these drugs could be effective for psychogenic or somatoform disorder-associated pain. This evidence also strongly suggested that serotonergic-noradrenergic antidepressants may have a more consistent antinociceptive effect than the serotonergic antidepressants. Finally, this evidence indicated that antidepressants could be effective for pain associated with some specific pain syndromes, such as chronic low back pain, osteoarthritis or rheumatoid arthritis, fibrositis or fibromyalgia, and ulcer healing. Possible reasons for the conflicting results of studies in this area are presented, and problems that could limit the validity of the conclusions of this review are discussed.

Monoamine oxidase inhibitors: safety and efficacy issues

Controversy has historically centered on the use of monoamine oxidase inhibitors (MAOI) in the treatment of depression because of safety and efficacy issues. Hypertensive crisis following ingestion of foods containing tyramine is the most feared problem associated with MAOI therapy. The authors conclude that only four tyramine-containing foods clearly warrant absolute prohibition, but indicate situations where moderation should apply. Although MAOI remain second-line agents in the treatment of endogenous depression, it is unclear whether MAOI or tricyclic antidepressants should be the drugs of choice in atypical depression and this question necessitates future research.

Platelet monoamine oxidase B: use and misuse

The human platelet in addition to having serotonin (5-HT) receptors, uptake carriers (receptor) and transmitter storage vesicles, primarily possesses mitochondrial monoamine oxidase (MAO) type B. Similar to the major form of MAO in the human brain, this enzyme actively oxidizes A-B and B substrates (tyramine, dopamine, phenylethylamine) as well as the novel secondary amine anticonvulsant, milacemide and dopaminergic neurotoxin, MPTP. 5-HT oxidation is hardly affected by the platelet enzyme and MAO inhibitors have no net effect on its accumulation. MAO-B is selectively inhibited by 1-deprenyl and thus the platelet enzyme may be useful to monitor the anti-Parkinson activity of such drugs, as related to their ability to inhibit brain MAO-B. The oxidation of the anticonvulsant, milacemide, to glycine in vitro and in vivo by MAO-B, may herald new prospects for the development of inert prodrugs capable of being metabolized to neuroactive substances by MAO-B. The plasma levels of their metabolites may be an index of MAO-B activity found in the platelet and brain.

Platelet MAO deamination of serotonin in depressed patients. Changes after imipramine treatment and clinical correlations

Monoamine oxidase (MAO) in blood platelets has been used as a model to study MAO in the central nervous system, where disorders in serotonergic systems are thought to occur in depression. Inconsistent changes in platelet MAO of depressed patients have been reported when several substrates other than serotonin (5-HT) have been used. To correlate changes in platelet MAO activity with the enzyme activity in central serotonergic systems, the platelet MAO activity of depressed patients (first unmedicated and then after 3 weeks and 2 months of imipramine treatment) and normal controls was measured using 5-HT as substrate. The results showed that there is a steady, measurable platelet MAO activity with that substrate. This activity was significantly higher in unmedicated depressed patients than in controls, and it decreased progressively with imipramine treatment, reaching a normal level when the patients were clinically recovered from depression after 2 months of therapy.

A pilot study of phenelzine in the treatment of post-traumatic stress disorder

In recent years, there has been renewed appreciation of the morbidity which can result from unusual or overwhelming stress and while many situations can give rise to post-traumatic disorder, the most frequently studied of these is probably military combat. Psychiatric disorder pursuant to combat experience can not only become chronic, but may intensify with advancing age, decades after the original trauma (Archibald & Tuddenbaum, 1965; Wilmer, 1982). Moreover, a high percentage of combat veterans are believed ultimately to develop chronic psychiatric morbidity (Walker & Cavenar, 1982). The drug treatment of such post-traumatic states remains an important question, largely over looked until the last 2 years but recent case reports suggest that doxepin and imipramine (White, 1983; Burstein, 1984) are beneficial in treating post traumatic stress disorder (PTSD), which may be either combat or non-combat related. Hogben & Cornfield (1981) described five veterans whose PTSD improved when treated with phenelzine, while Van der Kolk (1983) has described beneficial results with antidepressants, lithium, benzodiazepines, beta blockers, and neuroleptics in uncontrolled studies of PTSD.

Predicting treatment response in depressed and non-depressed chronic pain patients

Although it has often been observed that chronic pain and depression are associated, there have been few systematic comparisons of chronic pain patients with and without depression. In the study reported in this article, depressed and non-depressed chronic pain patients were found to be quite similar with respect to demographic, pain-related, and treatment response variables. The primary aim of the study, however, was to examine the hypothesis that treatment response in these two groups of patients would be predicted by different patterns of variables. In non-depressed patients, beneficial response to treatment was related to a greater number of treatment visits, not receiving workmen's compensation, fewer previous types of treatment, and low back pain. As predicted, a different pattern of predictors of treatment response was found for the depressed patients, who were more likely to benefit when they were employed at the beginning of treatment and when their pain was of shorter duration. These results suggest that activity and active involvement in treatment are particularly important with chronic pain patients who are depressed. In addition, they suggest that the best prediction of treatment response in future research on chronic pain patients may be achieved by dividing patients into groups based on psychological characteristics.

Forms of atypical depression and their response to antidepressant drugs

Three definitions of atypical depression are evaluated with respect to the effects of monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs) on the basis of pooled data from several double-blind studies. Those three definitions of atypical depression are depression with associated panic, depression secondary to a diagnosis of anxiety, and depression with reversed vegetative change. In none of these forms was a drug difference observed. However, when gender was taken into account, MAOIs were superior to TCAs in depressed women with panic attacks, whereas TCAs were superior to MAOIs in depressed men with panic attacks.

Neurovegetative symptoms in chronic pain and depression

The pattern and frequency of neurovegetative symptoms was studied in 57 patients with chronic pain. Seventy-nine percent of these patients had a diagnosable depressive illness, but endogenous depression was rare (5%). Patients with chronic pain were divided into major depressives, minor/intermittent depressives and patients with no depression. A control group of nonendogenous major depressives without pain was also utilized. Major depressives differed from the other two chronic pain groups in that there was more frequent or severe early waking, weight loss, anorexia, diminished libido and initial insomnia. Diurnal variation of mood was not a characteristic of major depression with chronic pain, and did not differ in frequency from the other two chronic pain groups. Major depressives exhibited a profile of neurovegetative symptoms very similar to that found in the control group of major depressives. Over one-third of minor/intermittent depressed patients with chronic pain exhibited atypical (reversed) vegetative symptoms of hyperphagia and weight gain. This finding, together with our review of the literature, suggests an important and previously unrecognized link between atypical depression and chronic pain.

Pyridoxine deficiency and peripheral neuropathy associated with long-term phenelzine therapy

A 51-year-old, nonalcoholic, nondiabetic woman with sensorimotor peripheral neuropathy and pyridoxine deficiency associated with long-term phenelzine therapy is described. Since phenelzine, like hydralazine and isoniazid, is a hydrazine capable of reducing pyridoxine levels in the rat, it is suggested that phenelzine, like hydralazine and isoniazid, may cause a pyridoxine-responsive peripheral neuropathy in humans.