Mirtazapine in combination with amitriptyline: a drug-drug interaction study in healthy subjects

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Pharmacokinetic Variability of Drugs Used for Prophylactic Treatment of Migraine

In this review, we evaluate the variability in the pharmacokinetics of 11 drugs with established prophylactic effects in migraine to facilitate 'personalized medicine' with these drugs. PubMed was searched for 'single-dose' and 'steady-state' pharmacokinetic studies of these 11 drugs. The maximum plasma concentration was reported in 248 single-dose and 115 steady-state pharmacokinetic studies, and the area under the plasma concentration-time curve was reported in 299 single-dose studies and 112 steady-state pharmacokinetic studies. For each study, the coefficient of variation was calculated for maximum plasma concentration and area under the plasma concentration-time curve, and we divided the drug variability into two categories; high variability, coefficient of variation >40%, or low or moderate variability, coefficient of variation <40%. Based on the area under the plasma concentration-time curve in steady-state studies, the following drugs have high pharmacokinetic variability: propranolol in 92% (33/36), metoprolol in 85% (33/39), and amitriptyline in 60% (3/5) of studies. The following drugs have low or moderate variability: atenolol in 100% (2/2), valproate in 100% (15/15), topiramate in 88% (7/8), and naproxen and candesartan in 100% (2/2) of studies. For drugs with low or moderate pharmacokinetic variability, treatment can start without initial titration of doses, whereas titration is used to possibly enhance tolerability of topiramate and amitriptyline. The very high pharmacokinetic variability of metoprolol and propranolol can result in very high plasma concentrations in a small minority of patients, and those drugs should therefore be titrated up from a low initial dose, depending mainly on the occurrence of adverse events.

Safety and tolerability of antidepressant co-treatment in acute major depressive disorder: results from a systematic review and exploratory meta-analysis

INTRODUCTION

Although antidepressant (AD) monotherapy is recommended first-line for major depressive disorder (MDD), AD + AD co-treatment is common.

AREAS COVERED

We conducted the first systematic review searching PubMed/MEDLINE/PsycInfo/Embase from database inception until 1 June 2015 for acute randomized trials in ≥ 20 adults with MDD comparing AD monotherapy with AD + AD co-treatment that reported quantitative data on adverse events (AEs). Meta-analyzing 23 studies (n = 2435, duration = 6.6 weeks) AD monotherapy and AD + AD co-treatment were similar regarding intolerability-related discontinuation (risk ratio [RR] = 1.38, 95% CI = 0.89 - 1.10) and frequency of ≥ 1 AE (RR = 1.19, 95% CI = 0.95 - 1.49). Nevertheless, AD + AD co-treatment was associated with significantly greater burden regarding 4/25 AEs (tremor: RR = 1.55, 95% CI = 1.01 - 2.38; sweating: RR = 1.95, 95% CI = 1.13 -3.38, ≥ 7% weight gain: RR = 3.15, 95% CI = 1.34 - 7.41; weight gain = 2.17, 95% CI = 0.71 - 3.63 kg), but not more CNS, gastrointestinal, sexual or alertness-related AEs. However, 11/25 AEs (44.0%) were reported in only 1 - 2 studies. Adding noradrenergic and specific serotonergic antidepressants (NaSSA) or tricyclic antidepressants (TCA) to selective serotonin reuptake inhibitors (SSRIs) was specifically associated with more AEs.

EXPERT OPINION

The potential for increased AEs with AD + AD co-treatment needs to be considered vis-à-vis unclear efficacy benefits of this strategy. In particular, NaSSAs and TCAs should be added to SSRIs with caution. Clearly, more data on side-effect burden of AD + AD co-treatment are needed.

What, if all alerts were specific - estimating the potential impact on drug interaction alert burden

PURPOSE

Clinical decision support systems (CDSS) may potentially improve prescribing quality, but are subject to poor user acceptance. Reasons for alert overriding have been identified and counterstrategies have been suggested; however, poor alert specificity, a prominent reason of alert overriding, has not been well addressed. This paper aims at structuring modulators that determine alert specificity and estimating their quantitative impact on alert burden.

METHODS

We developed and summarized optimizing strategies to guarantee the specificity of alerts and applied them to a set of 100 critical and frequent drug interaction (DDI) alerts. Hence, DDI alerts were classified as dynamic, i.e. potentially sensitive to prescription-, co-medication-, or patient-related factors that would change alert severity or render the alert inappropriate compared to static, i.e. always applicable alerts not modulated by cofactors.

RESULTS

Within the subset of 100 critical DDI alerts, only 10 alerts were considered as static and for 7 alerts, relevant factors are not generally available in today's patient charts or their consideration would not impact alert severity. The vast majority, i.e. 83 alerts, might require a decrease in alert severity due to factors related to the prescription (N=13), the co-medication (N=11), individual patient data (N=36), or combinations of them (N=23). Patient-related factors consisted mainly of three lab values, i.e. renal function, potassium, and therapeutic drug monitoring results.

CONCLUSION

This paper outlines how promising the refinement of knowledge bases is in order to increase specificity and decrease alert burden and suggests how to structure knowledge bases to refine DDI alerting.

Age-related changes in antidepressant pharmacokinetics and potential drug-drug interactions: a comparison of evidence-based literature and package insert information

BACKGROUND

Antidepressants are among the most commonly prescribed psychotropic agents for older patients. Little is known about the best source of pharmacotherapy information to consult about key factors necessary to safely prescribe these medications to older patients.

OBJECTIVE

The objective of this study was to synthesize and contrast information in the package insert (PI) with information found in the scientific literature about age-related changes of antidepressants in systemic clearance and potential pharmacokinetic drug-drug interactions (DDIs).

METHODS

A comprehensive search of two databases (MEDLINE and EMBASE from January 1, 1975 to September 30, 2011) with the use of a combination of search terms (antidepressants, pharmacokinetics, and drug interactions) was conducted to identify relevant English language articles. This information was independently reviewed by two researchers and synthesized into tables. These same two researchers examined the most up-to-date PIs for the 26 agents available at the time of the study to abstract quantitative information about age-related decline in systemic clearance and potential DDIs. The agreement between the two information sources was tested with κ statistics.

RESULTS

The literature reported age-related clearance changes for 13 antidepressants, whereas the PIs only had evidence about 4 antidepressants (κ < 0.4). Similarly, the literature identified 45 medications that could potentially interact with a specific antidepressant, whereas the PIs only provided evidence about 12 potential medication-antidepressant DDIs (κ < 0.4).

CONCLUSION

The evidence-based literature compared with PIs is the most complete pharmacotherapy information source about both age-related clearance changes and pharmacokinetic DDIs with antidepressants. Future rigorously designed observational studies are needed to examine the combined risk of antidepressants with age-related decline in clearance and potential DDIs on important health outcomes such as falls and fractures in older patients.

Clinically significant drug interactions with newer antidepressants

After the introduction of selective serotonin reuptake inhibitors (SSRIs), other newer antidepressants with different mechanisms of action have been introduced in clinical practice. Because antidepressants are commonly prescribed in combination with other medications used to treat co-morbid psychiatric or somatic disorders, they are likely to be involved in clinically significant drug interactions. This review examines the drug interaction profiles of the following newer antidepressants: escitalopram, venlafaxine, desvenlafaxine, duloxetine, milnacipran, mirtazapine, reboxetine, bupropion, agomelatine and vilazodone. In general, by virtue of a more selective mechanism of action and receptor profile, newer antidepressants carry a relatively low risk for pharmacodynamic drug interactions, at least as compared with first-generation antidepressants, i.e. monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs). On the other hand, they are susceptible to pharmacokinetic drug interactions. All new antidepressants are extensively metabolized in the liver by cytochrome P450 (CYP) isoenzymes, and therefore may be the target of metabolically based drug interactions. Concomitant administration of inhibitors or inducers of the CYP isoenzymes involved in the biotransformation of specific antidepressants may cause changes in their plasma concentrations. However, due to their relatively wide margin of safety, the consequences of such kinetic modifications are usually not clinically relevant. Conversely, some newer antidepressants may cause pharmacokinetic interactions through their ability to inhibit specific CYPs. With regard to this, duloxetine and bupropion are moderate inhibitors of CYP2D6. Therefore, potentially harmful drug interactions may occur when they are coadministered with substrates of these isoforms, especially compounds with a narrow therapeutic index. The other new antidepressants are only weak inhibitors or are not inhibitors of CYP isoforms at usual therapeutic concentrations and are not expected to affect the disposition of concomitantly administered medications. Although drug interactions with newer antidepressants are potentially, but rarely, clinically significant, the use of antidepressants with a more favourable drug interaction profile is advisable. Knowledge of the interaction potential of individual antidepressants is essential for safe prescribing and may help clinicians to predict and eventually avoid certain drug combinations.

Mirtazapine: a review of its use in major depression and other psychiatric disorders

Mirtazapine (Remeron, Zispin) is a noradrenergic and specific serotonergic antidepressant (NaSSA) that is approved in many counties for use in the treatment of major depression. Monotherapy with mirtazapine 15-45 mg/day leads to rapid and sustained improvements in depressive symptoms in patients with major depression, including the elderly. It is as effective as other antidepressants and may have a more rapid onset of action than selective serotonin reuptake inhibitors (SSRIs). Furthermore, it may also have a higher sustained remission rate than amitriptyline. Preliminary data suggest that mirtazapine may also be effective in the treatment of anxiety disorders (including post-traumatic stress disorder, panic disorder and social anxiety disorder), obsessive-compulsive disorder, undifferentiated somatoform disorder and, as add-on therapy, in schizophrenia, although large, well designed trials are needed to confirm these findings. Mirtazapine is generally well tolerated in patients with depression. In conclusion, mirtazapine is an effective antidepressant for the treatment of major depression and also has the potential to be of use in other psychiatric indications.

Clinically relevant pharmacokinetic drug interactions with second-generation antidepressants: an update

BACKGROUND

The second-generation antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), and other compounds with different mechanisms of action. All second-generation antidepressants are metabolized in the liver by the cytochrome P450 (CYP) enzyme system. Concomitant intake of inhibitors or inducers of the CYP isozymes involved in the biotransformation of specific antidepressants may alter plasma concentrations of these agents, although this effect is unlikely to be associated with clinically relevant interactions. Rather, concern about drug interactions with second-generation antidepressants is based on their in vitro potential to inhibit > or = 1 CYP isozyme.

OBJECTIVE

The goal of this article was to review the current literature on clinically relevant pharmacokinetic drug interactions with second-generation antidepressants.

METHODS

A search of MEDLINE and EMBASE was conducted for original research and review articles published in English between January 1985 and February 2008. Among the search terms were drug interactions, second-generation antidepressants, newer antidepressants, SSRIs, SNRIs, fluoxetine, paroxetine, fluvoxamine, sertraline, citalopram, escitalopram, venlafaxine, duloxetine, mirtazapine, reboxetine, bupropion, nefazodone, pharmacokinetics, drug metabolism, and cytochrome P450. Only articles published in peer-reviewed journals were included, and meeting abstracts were excluded. The reference lists of relevant articles were hand-searched for additional publications.

RESULTS

Second-generation antidepressants differ in their potential for pharmacokinetic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, and nefazodone is a substantial inhibitor of CYP3A4. Therefore, clinically relevant interactions may be expected when these antidepressants are coadministered with substrates of the pertinent isozymes, particularly those with a narrow therapeutic index. Duloxetine and bupropion are moderate inhibitors of CYP2D6, and sertraline may cause significant inhibition of this isoform, but only at high doses. Citalopram, escitalopram, venlafaxine, mirtazapine, and reboxetine are weak or negligible inhibitors of CYP isozymes in vitro and are less likely than other second-generation antidepressants to interact with co-administered medications.

CONCLUSIONS

Second-generation antidepressants are not equivalent in their potential for pharmacokinetic drug interactions. Although interactions may be predictable in specific circumstances, use of an antidepressant with a more favorable drug-interaction profile may be justified.

Neurocognitive costs and benefits of psychotropic medications in older adults

Psychotropic medications are widely used in older adults and may cause neurocognitive deficits. Older adults are at increased risk of developing adverse effects because of age-related pharmacodynamic and pharmacokinetic changes. This article provides a comprehensive review of the undesirable, and at times beneficial, effects of psychotropic medications. The review covers a wide range of medications that impair executive function, memory, and attention, as well as a much smaller group of medications that lead to improved neurocognitive function. Some of the most commonly used psychotropic medications in older adults, namely, antidepressants, sedatives, and hypnotics, are among the drugs that most consistently lead to cognitive impairments. Medications with anticholinergic properties almost invariably lead to neurocognitive dysfunction, despite symptom improvement. The neurocognitive costs and benefits of psychiatric medications should be considered in the context of disease treatment in older adults.

Inter- and intraindividual pharmacokinetic variations of mirtazapine and its N-demethyl metabolite in patients treated for major depressive disorder: a 6-month therapeutic drug monitoring study

Mirtazapine pharmacokinetic (PK) data from patients on long-term treatment for major depression have never been investigated. For this reason, in a large naturalistic outpatient study (prospective, multicenter, open-labeled, and noncomparative) conducted in Sweden in the period 2000-2002, one of the main objectives was to outline the inter- as well as intraindividual PK variance of mirtazapine and demethylmirtazapine serum concentrations in a patient cohort treated up to 6 (optionally 12) months. A total of 192 male and female outpatients aged 18 years or older were included. Serum samples of mirtazapine and demethylmirtazapine were collected, by the means of therapeutic drug monitoring, at weeks 1, 4, 8, and 24 (52). Altogether 683 serum samples were analyzed. A pronounced interindividual variability of mirtazapine and demethylmirtazapine, and the demethylmirtazapine/mirtazapine ratio was seen. The coefficient of variation was about 38%, 33%, and 36%, respectively. The intraindividual variation over time was low, about 20% on all variables. At the population level, no accumulation of mirtazapine, demethylmirtazapine, or change of the demethylmirtazapine/mirtazapine ratio was observed over time. Women had significantly higher dose-corrected concentrations of mirtazapine and demethylmirtazapine and demethylmirtazapine/mirtazapine ratio than men. Patients above 65 years of age had higher concentrations than their younger counterparts. Among patients with adverse events, lower demethylmirtazapine concentrations were observed than in patients with no adverse events. Patients on multiple drug treatment had higher dose-corrected mirtazapine and demethylmirtazapine serum concentrations than patients taking only mirtazapine. Weight and BMI had a significant negative correlation with demethylmirtazapine concentrations and with the demethylmirtazapine/mirtazapine ratio. Continued efforts are warranted to perform PK studies in a natural clinical setting to learn and understand inter- and intraindividual PK variances in real patients treated for longer periods of time. For mirtazapine as well as for most antidepressant drugs only relatively short term PK is available. To help clinicians improve their treatment of patients with major depressive disorder, the possible implications on the PK with a long-term treatment are important to study.

Tissue distribution of mirtazapine and desmethylmirtazapine in a case of mirtazapine poisoning

An ingestion of an unknown quantity of mirtazapine in a suicide attempt leading to death is described. Sertraline and amitriptyline have been co-ingested. Because mirtazapine is reported to be relatively safe in overdose, body fluids and tissues were investigated for both mirtazapine and desmethylmirtazapine by high-pressure liquid chromatography/tandem mass spectrometry following liquid-liquid extraction. The limit of detection was sufficiently low to also apply the assay in pharmacokinetic studies. The levels of amitriptyline and nortriptyline were very low (38 and 19 ng/mL femoral venous blood) and the amount of sertraline in blood taken from the femoral vein (880 ng/mL) was considerably lower than those seen in overdosage. Accumulation of mirtazapine and N-desmethylmirtazapine was evident in fluids and tissues involved in enterohepatic circulation and excretion. The concentration determined in a brain sample suggests a contribution of the metabolite to the drug's pharmacodynamic activity. Based on literature data, significant adverse or synergistic effects among the drugs detected as well as adverse reactions such as a serotonin reaction appeared less probable. Mirtazapine exhibits alpha(1)-antagonistic properties on the cardiac-vascular system and may cause hyponatraemia. In the face of the cardiac findings at autopsy and the lack of an apparent cause of death, these effects of mirtazapine may have initiated a process leading to death.