Clinical profile and serum concentration of viloxazine as compared to amitriptyline

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.

Amitriptyline for depression

BACKGROUND

For many years amitriptyline has been considered one of the reference compounds for the pharmacological treatment of depression. However, new tricyclic drugs, heterocyclic compounds and selective serotonin reuptake inhibitors have been introduced on the market with the claim of a more favourable tolerability/efficacy profile.

OBJECTIVES

The aim of the present systematic review was to investigate the tolerability and efficacy of amitriptyline in comparison with the other tricyclic/heterocyclic antidepressants and with the selective serotonin reuptake inhibitors.

SEARCH STRATEGY

The Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Register (CCDANCTR-Studies) was searched on 28-11-2005. Reference lists of all included studies were checked.

SELECTION CRITERIA

Only randomised controlled trials were included. Study participants were of either sex and any age with a primary diagnosis of depression. Included trials compared amitriptyline with another tricyclic/heterocyclic antidepressant or with one of the selective serotonin reuptake inhibitors.

DATA COLLECTION AND ANALYSIS

Data were extracted using a standardised form. The number of patients undergoing the randomisation procedure, the number of patients who completed the study and the number of improved patients were extracted. In addition, group mean scores at the end of the trial on Hamilton Depression Scale or any other depression scale were extracted. In the tolerability analysis, the number of patients failing to complete the study and the number of patients complaining of side-effects were extracted.

MAIN RESULTS

A total number of 194 studies were included in the review. The estimate of the overall odds ratio (OR) for responders showed that more subjects responded to amitriptyline in comparison with the control antidepressant group (OR 1.12 to 95% confidence interval (CI) 1.02 to 1.23, number needed to treat to benefit (NNTB) = 50). The estimate of the efficacy of amitriptyline and control agents on a continuous outcome revealed an effect size which also significantly favoured amitriptyline (Standardised Mean Difference (SMD) 0.13, 95% CI 0.04 to 0.23). Whilst these differences are statistically significant, their clinical significance is less clear. When the efficacy analysis was stratified by drug class, no difference in outcome emerged between amitriptyline and either tricyclic or selective serotonin reuptake inhibitor comparators. The dropout rate in patients taking amitriptyline and control agents was similar; however, the estimate of the proportion of patients who experienced side-effects significantly favoured control agents in comparison with amitriptyline (OR 0.66, 95% CI 0.59 to 0.74). When the tolerability analysis was stratified by drug class, the dropout rate in patients taking amitriptyline and the selective serotonin reuptake inhibitors significantly favoured the latter (OR 0.84, 95% CI 0.75 to 0.95, number needed to treat to harm (NNTH) = 40). When the responder analysis was stratified by study setting amitriptyline was more effective than control antidepressants in inpatients (OR 1.22, 95% CI 1.04 to 1.42, NNTB = 24), but not in outpatients (OR 1.01, 95%CI 0.88 to 1.17, NNTB = 200).

AUTHORS' CONCLUSIONS

This present systematic review indicates that amitriptyline is at least as efficacious as other tricyclics or newer compounds. However, the burden of side-effects in patients receiving it was greater. In comparison with selective serotonin reuptake inhibitors amitriptyline was less well tolerated, and although counterbalanced by a higher proportion of responders, the difference was not statistically significant.

The AGNP-TDM Expert Group Consensus Guidelines: focus on therapeutic monitoring of antidepressants

Therapeutic drug monitoring (TDM) of psychotropic drugs such as antidepressants has been widely introduced for optimization of pharmacotherapy in psychiatric patients. The interdisciplinary TDM group of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) has worked out consensus guidelines with the aim of providing psychiatrists and TDM laboratories with a tool to optimize the use of TDM. Five research-based levels of recommendation were defined with regard to routine monitoring of drug plasma concentrations: (i) strongly recommended; (ii) recommended; (iii) useful; (iv) probably useful; and (v) not recommended. In addition, a list of indications that justify the use of TDM is presented, eg, control of compliance, lack of clinical response or adverse effects at recommended doses, drug interactions, pharmacovigilance programs, presence of a genetic particularity concerning drug metabolism, and children, adolescents, and elderly patients. For some drugs, studies on therapeutic ranges are lacking, but target ranges for clinically relevant plasma concentrations are presented for most drugs, based on pharmacokinetic studies reported in the literature. For many antidepressants, a thorough analysis of the literature on studies dealing with the plasma concentration-clinical effectiveness relationship allowed inclusion of therapeutic ranges of plasma concentrations. In addition, recommendations are made with regard to the combination of pharmacogenetic (phenotyping or genotyping) tests with TDM. Finally, practical instructions are given for the laboratory practitioners and the treating physicians how to use TDM: preparation of TDM, drug analysis, reporting and interpretation of results, and adequate use of information for patient treatment TDM is a complex process that needs optimal interdisciplinary coordination of a procedure implicating patients, treating physicians, clinical pharmacologists, and clinical laboratory specialists. These consensus guidelines should be helpful for optimizing TDM of antidepressants.

Amitriptyline versus other types of pharmacotherapy for depression

BACKGROUND

For many years amitriptyline has been considered one of the reference compounds for the pharmacological treatment of depression. However, new tricyclic drugs, heterocyclic compounds and the selective serotonin reuptake inhibitors have been introduced on the market with the claim of a more favourable tolerability/efficacy profile.

OBJECTIVES

The aim of the present systematic review was to investigate the tolerability and efficacy of amitriptyline in comparison with the other tricyclic/heterocyclic antidepressants and with the selective serotonin reuptake inhibitors.

SEARCH STRATEGY

The Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Register (2002-3) and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched. Key journals and conference abstracts were handsearched. Pharmaceutical companies were contacted for information on unpublished materials.

SELECTION CRITERIA

Only randomised controlled trials were included. Study participants were of either sex and any age with a primary diagnosis of depression. Included trials compared amitriptyline with another tricyclic/heterocyclic antidepressant or with one of the selective serotonin reuptake inhibitors.

DATA COLLECTION AND ANALYSIS

Data were extracted using a standardised form. The number of patients undergoing the randomisation procedure, the number of patients who completed the study and the number of improved patients were extracted. In addition, group mean scores at the end of the trial on Hamilton Depression Scale or any other depression scale were extracted. In the tolerability analysis, the number of patients failing to complete the study and the number of patients complaining of side-effects was extracted.

MAIN RESULTS

The estimate of the overall odds ratio for responders showed that more subjects responded to amitriptyline in comparison with the control antidepressant group (odds ratio 1.12, 95% confidence interval 1.01, 1.23, number needed to treat 50). The estimate of the efficacy of amitriptyline and control agents on a continuous outcome revealed an effect size which also significantly favoured amitriptyline (Standardised Mean Difference 0.13, 95% confidence interval 0.04, 0.23). Whilst these differences are statistically significant, their clinical significance is less clear. When the efficacy analysis was stratified by drug class, no difference in outcome emerged between amitriptyline and either tricyclic or selective serotonin reuptake inhibitor comparators. The dropout rate in patients taking amitriptyline and control agents was similar; however, the estimate of the proportion of patients who experienced side-effects significantly favoured control agents in comparison with amitriptyline (odds ratio 0.63, 95% confidence interval 0.56, 0.71). When the tolerability analysis was stratified by drug class, the dropout rate in patients taking amitriptyline and the selective serotonin reuptake inhibitors significantly favoured the latter (odds ratio 0.84, 95% confidence interval 0.75,0.95, number needed to harm 40). When the responder analysis was stratified by study setting amitriptyline was more effective than control ADs in inpatients (odds ratio 1.22, 95% confidence interval 1.04, 1.42, number needed to treat 24), but not in outpatients (odds ratio 1.01, 95% confidence interval 0.88, 1.17, number needed to treat = 200).

REVIEWER'S CONCLUSIONS

This present systematic review indicates that amitriptyline is at least as efficacious as other tricyclics or newer compounds. However, the burden of side-effects in patients receiving it was greater. In comparison with the selective serotonin reuptake inhibitors amitriptyline was less well tolerated, and although counterbalanced by a higher proportion of responders, the difference was not statistically significant.

Amitriptyline v. the rest: still the leading antidepressant after 40 years of randomised controlled trials

BACKGROUND

Tricyclic antidepressants have similar efficacy and slightly lower tolerability than selective serotonin reuptake inhibitors (SSRIs). However, there are no systematic reviews assessing amitriptyline, the reference tricyclic drug, v. other tricyclics and SSRIs directly.

AIMS

To review the tolerability and efficacy of amitriptyline in the management of depression.

METHOD

A systematic review of randomised controlled trials (RCTs) comparing amitriptyline with other tricyclics/heterocyclics or with an SSRI.

RESULTS

We reviewed 186 RCTs. The overall estimate of the efficacy of amitriptyline revealed a standardised mean difference of 0.147 (95% CI 0.05-0.243), significantly favouring amitriptyline. The overall OR for dropping out was 0.99 (95% CI 0.91-1.08) and that for side-effects was 0.62 (95% CI 0.54-0.70), favouring the control drugs. With drop-outs included as treatment failures, the estimate of the effectiveness of amitriptyline v. tricyclics/heterocyclics and SSRIs showed a 2.5% difference in the proportion of responders in favour of amitriptyline (number needed to treat 40, CI 21-694; OR 1.12 (95% CI 1.01-1.24)).

CONCLUSIONS

Amitriptyline is less well tolerated than tricyclics/heterocyclics and SSRIs, but slightly more patients treated on it recover than on alternative antidepressants.

All-night EEG spectral analysis as a tool for the prediction of clinical response to antidepressant treatment

Earlier investigations have suggested that variables derived from quantified electroencephalographic (EEG) sleep analysis might predict good clinical response in an early phase of antidepressant treatment. In this report we evaluate the predictive value of all-night sleep EEG spectral analysis during the washout period before treatment. We compared the spectral EEG sleep profiles of major depressed inpatients divided into two groups according to an improvement > or = 50% on the Hamilton Rating Scale for Depression. Findings in this population demonstrate the presence of specific characteristics of the responder group compared with the nonresponder group. Delta band relative power was increased in the former group, while theta, alpha, and beta relative power were decreased. All the bands showed decrease in absolute power in the responder group. These results can be interpreted as enhanced sleep intensity in the responder group. All-night sleep EEG spectral variables are valid baseline markers of the functional differences between treatment responders and nonresponders and thus might permit prediction of clinical outcome.

Pharmacokinetic optimisation of therapy with newer antidepressants

Since the early 1950s, when imipramine was first introduced, a whole series of antidepressants with differences in structures, neurochemical effects and pharmacokinetics have been developed. Structurally or functionally, they have been classified as tricyclic antidepressants (TCAs), tetracyclic antidepressants, monoamine oxidase inhibitors (MAOIs), or selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs). In addition, there is a series of antidepressants with unique structures. Many of the newer TCAs appear to have shorter half-lives than the standard TCAs (e.g. imipramine), allowing for the possibility of a more rapid response, but requiring the drugs to be given in multiple daily doses, which may reduce patient compliance. The short time to peak plasma concentration (tmax) can also lead to rapid onset of adverse effects. The tetracyclic antidepressants have longer elimination half-lives (t1/2) than the TCAs, but there is only very minimal evidence for a relationship between drug concentrations in the blood and clinical response. The triazolopyridines, like the newer TCAs, show pharmacokinetic evidence for rapid onset of adverse effects and the need for multiple daily doses due to short tmax and t1/2. The newer MAOIs are a significant addition to therapy, as the rapid binding action of these medications increases their safety margin with regard to tyramine interactions. Further information in this area is required. In addition, moclobemide has pharmacokinetic features that are clinically beneficial (e.g. aging and renal dysfunction have little effect on the elimination of the drug), but also features that are not beneficial (e.g. nonlinear pharmacokinetics). Among the SSRIs, there are a range of t1/2 values for the parent drugs, from relatively short t1/2 values of less than 24 hours (paroxetine, fluvoxamine) to among the longest found (e.g. 2 days for fluoxetine). Only 2 of the agents (sertraline and citalopram) have linear pharmacokinetics, and 1 drug has nonlinear pharmacokinetics within the usual therapeutic range (fluvoxamine). Once a therapeutic blood concentration is established, linearity is helpful in avoiding the small dose changes and repeated rechecking of concentrations of medications that would be required for those agents with nonlinear pharmacokinetics. Sertraline stands out as having the best effects on behaviour among all antidepressants. However, fluoxetine and fluvoxamine are least likely to penetrate into breast milk. All 3 of the structurally unique newer antidepressants [amfebutamone (bupropion), viloxazine venlafaxine] have relatively short tmax values (1 to 2 hours), which may relate to the early onset of adverse effects. Amfebutamone has the benefits of linear pharmacokinetics with potential for defined therapeutic blood concentrations, lack of effect of liver enzymes on metabolism of the drug, and lack of significant effects of either aging or hepatic dysfunction on elimination of the drug. Thus, the antidepressants best suited for pharmacokinetic optimisation of therapy are the following: desipramine, sertraline, fluvoxamine, citalopram and amfebutamone.

Drug effects on REM sleep and on endogenous depression

In earlier work REM sleep deprivation (RSD) by arousals improved endogenous depression. This suggested that drugs producing a similar RSD would have antidepressant activity. The arousal RSD was large, persisted for weeks, and was followed by a REM rebound. We call RSD with these properties arousal-type RSD. The present study reviewed literature from 1962 to 1989 on drug REM sleep effects to examine the hypothesis that drugs producing arousal-type RSD improve endogenous depression. The literature reviewed concerned the REM sleep effects of amine precursors, antidepressants, antihistamines, antipsychotics, barbiturates, benzodiazepines, other hypnotics, drugs affecting cholinergic and noradrenergic neurotransmission, ethanol, lithium and narcotics. Four hundred and sixty-eight relevant papers were read and 215 contributed information that could be used in the review. The findings indicated that all drugs producing arousal-type RSD improved endogenous depression. Four drugs that improved endogenous depression did not produce arousal-type RSD.

Trazodone in endogenous depressed patients: a negative report and a critical evaluation of the pertaining literature

The antidepressant efficacy of trazodone has been studied during three weeks in 13 endogenously depressed patients, using a fixed dosage of 5/10 mg/kg bodyweight per day. Psychopathological assessments were documented by means of observer rating (HDRS, AMP) and selfratings (Bf-S, EWL-K). Most variables assessed during course of treatment did not reveal amelioration of statistical significance or clinical relevance. If the most frequently applied response criteria of a 50% reduction of the initial HDRS-score was taken, only three patient improved. Those results were surprising in view of the previous and subsequent response to antidepressant therapy of the patient group studied. Plasmalevels of trazodone were monitored once weekly; they showed a nine-fold interindividual variation and did not correlate to the fixed dosage steps. A critical review of the pertaining literature led the authors assume, that the main indication of this drug is within non-endogenous-depression.

Psychiatric clinic of the Free University of Berlin; Department of Clinical Psychiatry and Polyclinic

The Department of Psychiatry in its present form has developed since 1968, when the psychiatric branch of the Psychiatrische und Neurologische Klinik (Psychiatric and Neurological Clinic), the traditional type of a West German university hospital comprising psychiatry and neurology in one chair, became autonomous with the establishment of an independent chair of psychiatry. This was an early step in the separation of psychiatry and neurology, a situation which is now to be seen in all German universities. Moreover, during the last decade almost all psychiatric university departments have been more or less sub-divided into sub-specialities. This process has been carried to its furthest extreme in West Berlin which now has departments of clinical psychiatry, geronto-psychiatry, social psychiatry, psychosomatics, child and adolescent psychiatry, neuropsychopharmacology, psychophysiology, student mental health, and forensic psychiatry. The lines of demarcation have been drawn according to somewhat divergent (historical, personal, conceptual) criteria, so that the individual departments differ in size, research interests and research facilities. More than 10 professors, 15 senior doctors and about 50 assistants (physicians, psychologists, sociologists, mathematicians, chemists and engineers) make up a critical mass, but centrifugal forces are often dominant and restrain the optimal use of all facilities for real interdisciplinary collaboration in the sense of what has been described as the ‘agricultural’ approach to research (Shepherd, 1981).

Plasma levels, psychophysiological variables, and clinical response to amitriptyline

Hamilton depression scale ratings and physiological measurements were made for 37 patients with primary depression before treatment with amitriptyline (150 mg/day) and again after 2 and 4 weeks of treatment; plasma drug levels were determined weekly. Improvement was maximal at mean amitriptyline + nortriptyline concentrations of 125-200 ng/ml (14 patients), while at lower levels the outcome was significantly poorer (12 patients). Highly variable results were seen in 11 patients with levels between 200 and 301 ng/ml, with lesser improvement occurring in those patients who exhibited poor habituation of the skin resistance response before treatment. Other psychophysiological variables showed significant changes during treatment, but no correlation with clinical results or drug levels.

Anticonvulsant and proconvulsant properties of viloxazine hydrochloride: pharmacological and pharmacokinetic studies in rodents and the epileptic baboon

Viloxazine HCl is evaluated as an anticonvulsant in a wide range of rodent seizure models and in the epileptic baboon (Papio papio). In the maximal electroshock test, the oral ED50 for abolition of tonic extension was 9 mg/kg-1 after 30-min pretreatment (mouse) rising to 30 mg/kg-1 after 60 min (mouse and rat). Comparable ED50 values were also found for protection against tonic extension in the mouse induced by the administration of the chemical convulsants metrazole or 3-mercaptopropionic acid. In DBA/2 mice the ED50 for abolition of tonic extension during sound-induced seizures was 6.8 mg/kg-1 IP (30-min pretreatment). Pharmacokinetic studies in the mouse showed peak plasma levels to occur 30 min following oral doses, with a mean half-life of 58 min. The anticonvulsant plasma concentration was within 0.5 -- 1 microgram/ml-1. In the baboon, significant protection against photomyoclonic responses is observed 1 -- 2h after viloxazine (2.6 mg/kg-1 IV), during which period the plasma concentration was again 0.5-1 microgram/ml-1. After administration of approximately ten-times this latter dose level, i.e. 24 mg/kg-1 IV, a syndrome characterised by an abnormal EEG and, in some instances, seizure activity was observed.

Pharmacokinetics of viloxazine hydrochloride in man

The pharmacokinetic characteristics of a new antidepressant, viloxazine hydrochloride, were investigated in five males and five females to study sex differences. Plasma levels were determined over a period of 9 h after a single dose of viloxazine of 100 mg (expressed as base). The half life of the drug was in the range of 2.19 - 4.21 for females and 2.61 - 4.31 h for males. The maximum plasma levels occurred in 29 - 171 min of the oral dose for females and 54 - 155 min for males. They reached 1382 - 1769 ng/ml-l for females and 1108 - 2932 ng/ml for males. Pharmacokinetic data were not statistically different between males and females.

Viloxazine and the depressed schizophrenic--methodological issues

A pilot study of a small group of schizophrenic patients manifesting symptoms of a depressive nature was treated in a double-blind study in which viloxazine or a placebo was administered in combination with either chlorpromazine or haloperidol. There appeared to be no difference between the viloxazine-treated group and the placebo-treated group, although the study raised some question as to the adequacies of the dosage utilized since there was an absence of any apparent side effects. In view of these issues concerning the clinical merit of the combination, this obviously requires further investigation.

Viloxazine plasma concentrations and clinical response

Eleven patients suffering from primary depressive illness were treated with 300 mg/d of viloxazine for 29 days. Blood samples were collected at weekly intervals and severity of depression assessed using the Hamilton depression rating scale. Mean plasma viloxazine level for all patients during the trial was 1.20 micrograms/ml and ranged from 0.40 to 2.70 micrograms/ml. No simple relationship between plasma concentration and amelioration score was observed at day (rs = -0.02), day 22 (rs = -0.29) or day 29 (rs = 0.09). No significant difference in plasma concentrations between responders and non-responders was observed at day 29. Side effects were not correlated with plasma concentrations.