Plasma nortriptyline and clinical response in depression

Monitoring of tricyclic antidepressant plasma levels and clinical response: a review of the literature. Part I

Part I of this paper presents a comprehensive review of plasma level monitoring of tricyclic antidepressants (TCAs) and their relationship to clinical response to antidepressant therapy. Imipramine, nortriptyline, amitriptyline, clomipramine and desipramine are the most widely studied TCAs in this regard. Typical therapeutic plasma concentration ranges are suggested for some of these agents, although a consensus is lacking.

Bupropion: pharmacology and therapeutic applications

A total of 17 years after its introduction, bupropion remains a safe and effective antidepressant, suitable for first-line use. Bupropion undergoes metabolic transformation to an active metabolite, 4-hydroxybupropion, through hepatic cytochrome P450-2B6 (CYP2B6) and has inhibitory effects on cytochrome P450-2D6 (CYP2D6), thus raising concern for clinically-relevant drug interactions. Common side effects are nervousness and insomnia. Nausea appears slightly less common than with the SSRI drugs and sexual dysfunction is probably the least of any antidepressant. Bupropion is relatively safe in overdose with seizures being the predominant concern. The mechanism of action of bupropion is still uncertain but may be related to inhibition of presynaptic dopamine and norepinephrine reuptake transporters. The activity of vesicular monoamine transporter-2, the transporter pumping dopamine, norepinephrine and serotonin from the cytosol into presynaptic vesicles, is increased by bupropion and may be a component of its mechanism of action. Bupropion is approved for use in major depression and seasonal affective disorder and has demonstrated comparable efficacy to other antidepressants in clinical trials. Bupropion is also useful in augmenting a partial response to selective serotonin reuptake inhibitor antidepressants, although bupropion should not be combined with monoamine oxidase inhibitors. It may be less likely to provoke mania than antidepressants with prominent serotonergic effects. Bupropion is effective in helping people quit tobacco smoking. Anecdotal reports indicate bupropion may lower inflammatory mediators such as tumor necrosis factor-alpha, may lower fatigue in cancer and may help reduce concentration problems.

Is dose escalation of antidepressants a rational strategy after a medium-dose treatment has failed? A systematic review

BACKGROUND

Maximizing the dose of antidepressants is widely recommended in cases of non-response to medium-dose treatment. However, scientific evidence supporting high-dose treatment is scarce. Systematic studies comparing dose escalation with alternative strategies for refractory depression (i. e. augmentation or change of compound) are lacking. The aim of this publication is to review available direct and indirect evidence concerning dose increase of antidepressants after a medium-dose trial has failed.

METHOD

We performed a systematic literature search of Medline (1966-2003) and reviewed studies and publication references for available evidence.

DATA SOURCES AND STUDY SELECTION

Studies of the following types were included: 1) dose increase studies in treatment refractory patients, 2) comparative dose studies, 3) therapeutic drug monitoring studies.

RESULTS

Available data suggest differential efficacy of various pharmacological classes at more than medium-dosage. Direct evidence shows no increase of efficacy with high-dose selective serotonin reuptake inhibitor (SSRI) treatment; however, indirect evidence suggests enhanced therapeutic efficacy with high-dose tricyclic antidepressants. Few clinical data show ultra-high-dose treatment with the irreversible monoamine-oxidase-(MAO-) inhibitor tranylcypromine to be effective for refractory depression. Data concerning other selective compounds are insufficient to allow any definitive conclusion on the benefit of high-dose treatment.

CONCLUSIONS

Based on available data highdose antidepressant treatment of patients refractory to medium-dose treatment is recommended for tricyclic compounds but not for SSRI. Some data suggest beneficial efficacy of ultra-high doses of the irreversible MAOI tranylcypromine. Research on other substance groups is limited and inconclusive. Prospective studies comparing dose escalation with alternative strategies for treatment of non-responding patients are needed.

Nortriptyline blood levels and clinical outcome: meta-analysis of published studies

INTRODUCTION: An optimum range has been suggested for nortriptyline blood levels, above or below which patients respond poorly or do not respond at all to treatment. METHODS: A meta-analysis of published studies was performed to verify the existence of an optimal blood concentration range or therapeutic window in nortriptyline-treated depression patients. A MEDLINE search through the years 1970-1999 was carried out to identify original papers and review articles. Data concerning blood levels and percentage improvement were obtained concerning all included pacients. Univariate and multivariate analyses were performed for data comparison. Possible confounding variables, such as pre-treatment, setting (in or outpatients), and duration of treatment were also evaluated. RESULTS: From the 22 published studies found, only six of them with patients' individual data were included. We found an optimal range for nortriptyline concentrations (OR= 2.25, 95% CI = 1.15 to 4.39, p= 0.02). CONCLUSIONS: There may be a biphasic relationship of efficacy to plasma concentrations of nortriptyline, with a therapeutic window between 46 to 236 ng/ml.