Therapeutic drug monitoring of tricyclic antidepressants: how does it work under clinical conditions?

Therapeutic Drug Monitoring in Psychiatry: Enhancing Treatment Precision and Patient Outcomes

Psychiatric disorders often require pharmacological interventions to alleviate symptoms and improve quality of life. However, achieving an optimal therapeutic outcome is challenging due to several factors, including variability in the individual response, inter-individual differences in drug metabolism, and drug interactions in polytherapy. Therapeutic drug monitoring (TDM), by measuring drug concentrations in biological samples, represents a valuable tool to address these challenges, by tailoring medication regimens to each individual. This review analyzes the current landscape of TDM in psychiatric practice, highlighting its significance in optimizing drug dosages, minimizing adverse effects, and improving therapeutic efficacy. The metabolism of psychiatric medications (i.e., mood stabilizers, antipsychotics, antidepressants) often exhibits significant inter-patient variability. TDM can help address this variability by enhancing treatment personalization, facilitating early suboptimal- or toxic-level detection, and allowing for timely interventions to prevent treatment failure or adverse effects. Furthermore, this review briefly discusses technological advancements and analytical methods supporting the implementation of TDM in psychiatric settings. These innovations enable quick and cost-effective drug concentration measurements, fostering the widespread adoption of TDM as a routine practice in psychiatric care. In conclusion, the integration of TDM in psychiatry can improve treatment outcomes by individualizing medication regimens within the so-called precision medicine.

Chronic Doxepin Toxicity Masquerading as Epilepsy in a 10-Year-Old Boy

INTRODUCTION

Chronic tricyclic antidepressant toxicity is rarely described in children. Symptoms include confusion, ataxia, and seizures. Toxicity may result from dosing error, CYP2C19 and CYP2D6 genetic variability, and drug-drug interactions. Chronic doxepin toxicity has not been previously reported in children. Doxepin is prescribed for insomnia and depression, with a maximum off-label dose of 3 mg/kg in children. We present a case of chronic doxepin toxicity mimicking epilepsy in a child attributable to three potential factors: supratherapeutic dosing, pharmacogenomic variability, and drug-drug interactions.

CASE REPORT

A 10-year-old boy with insomnia, diagnosed with epilepsy 6 months prior, presented to an emergency department with confusion, ataxia, and increasing seizure frequency. He was prescribed doxepin for insomnia and four antiepileptics for seizures. After admission, he had two seizures and remained confused. EKGs showed QRS prolongation, suggesting doxepin toxicity. Doxepin-nordoxepin combined serum concentration was 1419 ng/mL (therapeutic 100-300 ng/mL), confirming doxepin toxicity. Outpatient records showed onset of confusion and seizures as doxepin dose was gradually uptitrated to 300 mg nightly (4.41 mg/kg). Symptoms worsened following addition of clobazam (CYP2D6 inhibitor) and topiramate (CYP2C19 inhibitor). Following doxepin discontinuation, all symptoms resolved. CYP2D6 testing showed intermediate metabolizer phenotype (CYP2D6*1/*4; activity score = 1.0; copy number = 2.0). No seizures have occurred in more than one year since doxepin discontinuation.

DISCUSSION

Caution must be exercised when prescribing doxepin. Pharmacogenomics, dose, drug-drug interactions, and age should be considered. Chronic toxicity should be contemplated in patients taking doxepin without acute overdose who present with persistent neurologic abnormalities including seizure.

Antidepressant efficacy is correlated with plasma levels: mega-analysis and further evidence

The debate around optimal target dose for first-line antidepressants (ADs) is still ongoing. Along this line, therapeutic drug monitoring (TDM) represents one of the most promising tools to improve clinical outcome. Nevertheless, a few data exist regarding the concentration-effect relationship of first-line ADs which limits TDM implementation in routine clinical practice. We conducted the first patient-level concentration-response mega-analysis including data acquired by us previously and explored the concentration dependency of first-line AD (206 subjects). Further, new data on mirtazapine are reported (18 subjects). Hamilton Depression Rating Scale-21 administered at baseline, at month 1 and month 3 was used as the measure of efficacy to assess antidepressant response (AR). When pooling all four first-line ADs together, normalized plasma levels and AR significantly fit a bell-shaped quadratic function with a progressive increase of AR up to around the upper normalized limit of the therapeutic reference range with a decrease of AR at higher serum levels. Our results complement the available evidence on the issue and the recent insights gained from dose-response studies. A concentration-dependent clinical efficacy, such as previously demonstrated for tricyclic compounds, also emerge for first-line ADs. Our study supports a role for TDM as a tool to optimize AD treatment to obtain maximum benefit.

Optimizing doxepin therapy in dermatology: introducing blood level monitoring and genotype testing

Doxepin, a tricyclic antidepressant, is the most efficacious antipruritic available to dermatologists; however its use is often suboptimal because of significant interindividual variability in doxepin plasma levels and clinical response between patients taking the same dose. As result, the Food and Drug Administration approves a maximum dose of 300 mg of doxepin per day and a 10 mg per cc liquid doxepin concentrate. These allow patients to significantly increase or decrease their dose, due to either a lack of clinical efficacy or side effects at typical dermatologic doses (often 10-25 mg per day). This review initially discusses the unique advantages of doxepin in dermatology. Then, it explores internal and external reasons why doxepin plasma levels and clinical response vary so significantly between patients, including genetic polymorphisms, drug interactions, comorbidities, sex, and ethnicity. Blood level monitoring is introduced, a tool dermatologists can use to optimize doxepin dosing in patients responding subtherapeutically to typical dermatologic doses. Without blood level monitoring, patients initially unresponsive to treatment could be labeled treatment failures when in fact they may be cases of inadequate dosing. Blood level monitoring allows for safe dose adjustments in these individuals to maximize patients' chances of achieving therapeutic success with this agent.

A 5-Year Study of Lithium and Valproic Acid Drug Monitoring in Patients with Bipolar Disorders in an Italian Clinical Center

Therapeutic drug monitoring (TDM) is an effective tool used to improve the pharmacological treatment in clinical practice, especially to detect subtherapeutic drug plasma concentration (Cp) in order to consider a change of dosage during treatment and reach its putative therapeutic range. In this study, we report the Cp values of lithium and valproic acid (VPA), alone and in combination, mostly in bipolar patients admitted to an Italian clinical center of the University of Pisa during the years 2016–2020, which include 12,294 samples of VPA, 7449 of lithium and 1118 of both in combination. Lithium and VPA are the most utilized drugs in treating bipolar disorders, and their TDM is strongly recommended by recent guidelines. In relation to lithium Cp monitoring, several studies have underlined that 0.5–0.8 mmol/L is the optimal range for chronic treatment, and below 0.4 mmol/L, it is unlikely to produce a clinical response. For VPA, the therapeutic range is 50–100 μg/mL and a linear correlation between Cp and clinical efficacy has been proposed, where below 50 μg/mL, the clinical efficacy of VPA has not been proven thus far. Toxic levels of both drugs were rarely found in our study, while a high percentage of patients, about one-third, had sub-therapeutic Cp during their treatments. In addition, in several cases of patients receiving multiple blood sampling, the initial subtherapeutic Cp changed only partially without reaching its therapeutic window. In relation to age, we found a higher percentage of lithium and VPA Cp values in range in the adolescents than in the adults and elderly groups. No differences were reported when analyzing the distribution of Cp values in males and females. In conclusion, this present study suggests that TDM is widely used by many specialists, but there is still a window of improvement for optimizing pharmacological treatments in clinical practice.

Analysis of smoking behavior on the pharmacokinetics of antidepressants and antipsychotics: evidence for the role of alternative pathways apart from CYP1A2

Smoking is common among psychiatric patients and has been shown to accelerate the metabolism of different drugs. We aimed to determine the effect of smoking on the serum concentrations of psychopharmacological drugs in a naturalistic clinical setting. Dose-corrected, steady-state serum concentrations of individual patients were analyzed retrospectively by linear regression including age, sex, and smoking for amitriptyline (n=503), doxepin (n=198), mirtazapine (n=572), venlafaxine (n=534), clozapine (n=106), quetiapine (n=182), and risperidone (n=136). Serum levels of amitriptyline (P=0.038), clozapine (P=0.02), and mirtazapine (P=0.002) were significantly lower in smokers compared with nonsmokers after correction for age and sex. In addition, the ratios of nortriptyline/amitriptyline (P=0.001) and nordoxepin/doxepin (P=0.014) were significantly higher in smokers compared with nonsmokers. Smoking may not only induce CYP1A2, but may possibly also affect CYP2C19. Furthermore, CYP3A4, UGT1A3, and UGT1A4 might be induced by tobacco smoke. Hence, a different dosing strategy is required among smoking and nonsmoking patients. Nevertheless, the clinical relevance of the results remained unclear.

Serum N-Desmethylcitalopram Concentrations are Associated with the Clinical Response to Citalopram of Patients with Major Depression

OBJECTIVE

Citalopram (CITA) is a widely used and well-tolerated selective serotonin reuptake inhibitor. The aim of the study was to evaluate the possible influences of serum concentrations of CITA and its major metabolite n-desmethylcitalopram (NDCITA) on the efficacy and tolerability of CITA in patients with major depressive disorder.

METHODS

The study included 46 outpatients with major depressive disorder who received CITA. The efficacy and tolerability were assessed for 6 weeks. Serum CITA and NDCITA levels were measured at the 4th week.

RESULTS

The HDRS17 total scores of the patients with high NDCITA and CITA & NDCITA concentrations showed a more significant reduction compared to the patients with expected and low serum NDCITA and CITA & NDCITA concentrations. However, we did not observe a correlation between the serum concentrations and the side effects of CITA, NDCITA, and CITA & NDCITA.

CONCLUSION

Our results suggested the potential contribution of NDCITA to the antidepressant effect of CITA. Further studies involving larger clinical samples are required to confirm the impact of serum NDCITA concentrations on the efficacy of CITA.

[From the Competence Network on Depression and Suicidality to the German Depression Foundation. National and international prevention of suicidal behaviour and optimizing health care through using of E‑Mental-Health]

Depression is a very common, severe, socio-economically highly relevant disorder and the main cause for approximately 10,000 suicides in Germany annually. There is capital room for improvement and optimization of the care for depressed patients, as effective and evidence-based treatment options are available. However, they are only used optimally by a minority of the people affected due to huge diagnostic and therapeutic deficits. The "Compentence Network on Depression and Suicidality" provided several evidence-based concepts to improve care for patients affected by depression and to prevent suicidal behaviour. Especially the four-level intervention approach of the Alliances Against Depression has been successfully adapted and implemented by more than 100 regions within Europe and globally as well. The infrastructure of the Competence Network could be efficiently sustained throughout the establishment of the German Depression Foundation and the European Alliance against Depression. Since 2014, all research activities have been extended nationally and internationally by the establishment of a Depression Research Centre with a special focus on various E‑Mental-Health-projects.

Utilization of antipsychotic therapeutic drug monitoring at a state psychiatric hospital

Introduction

This study assesses the utilization of antipsychotic therapeutic drug monitoring (TDM) and describes characteristics of appropriate and inappropriate TDM at a state psychiatric hospital.

Methods

A retrospective, descriptive review was conducted for antipsychotic TDM completed between December 1, 2009, and June 30, 2011, at a 65-bed adult inpatient extended-care and forensic state psychiatric hospital.

Results

One hundred thirty-three (n = 133) antipsychotic serum levels were collected from 44 patients during the study period. Sixty-nine percent (69%) of the TDM were deemed inappropriate, 28% were appropriate, and 3% could not be designated appropriate or inappropriate owing to the lack of information regarding steady-state conditions. The primary reason for inappropriate TDM was lack of documentation with regard to the indication for TDM (n = 79, 59.3%), the intervention following laboratory analysis (n = 88, 66%), or both. Appropriate TDM was associated with a lower laboratory cost for antipsychotic serum level ($48.98 ± $53.49 versus $72.06 ± $51.02, P < .05), lower daily cost of scheduled psychiatric medications ($17.72 ± $23.03 versus $32.26 ± $31.05, P < .05), lower daily cost of total medications ($19.28 ± $24.91 versus $33.82 ± $31.03, P < .05), fewer scheduled psychiatric medications (2.95 ± 1.90 versus 4.04 ± 2.19, P < .01), and fewer total scheduled medications (5.95 ± 3.60 versus 7.60 ± 3.29, P < .05). Inappropriate TDM led to approximately $6,753 in avoidable laboratory costs over a 20-month period.

Discussion

Therapeutic drug monitoring is a complex process with many points at which errors may occur. The majority of antipsychotic levels at this state psychiatric hospital were not documented in a way that was clinically useful. Inappropriate TDM was associated with increased laboratory and medication costs.

Determination of blood concentration levels of psychotropic medications in Rwandan patients

OBJECTIVES

In Rwanda, no therapeutic monitoring of psychotropic drugs is done. This results in difficult treatment optimisation and exposition to a high risk of toxicity and drug ineffectiveness for patients under treatment. This study aimed to determine blood concentration levels of psychotropic drugs in Rwandan patients and identify problems associated with the lack of therapeutic drug monitoring (TDM) of these drugs.

METHODS

The analysis was performed on 1 ml of serum sample using prazepam as internal standard. Regarding the step of sample preparation, we used a liquid-liquid extraction with a mixture of organic solvents: diethyl ether/dichloromethane/hexane/n-amyl alcohol (50/30/20/0.5:V/V). A Waters Alliance 2695 was used for analysis. The chromatography was run on a Symmetry C8 column and as mobile phase acetonitrile and phosphate buffer (pH 3.8) were used.

RESULTS

Concerning the results, serum samples from 128 patients were analysed. Twenty-one different psychotropic drugs belonging to various pharmacological classes were detected and quantified. Analytical results were put into three categories based upon therapeutic reference ranges (TRR) of various drugs: subtherapeutic, therapeutic and supratherapeutic. For a total of 237 analyses, results within TRR represented 46% while 47 and 8% of results were, respectively, below and above TRR.

CONCLUSION

It was therefore concluded that patients under psychotropic treatment in Rwanda are exposed to both the risk of drug ineffectiveness and the risk of toxicity (54%) with only 46% of results within the TRR. Consequently, TDM is needed to optimise psychotropic treatment in Rwandan patients.

Therapeutic drug monitoring: perspectives of psychiatrists in Turkey

OBJECTIVES

Although the medical and economic implications of therapeutic drug monitoring have been intensely discussed over the past years, little is known about the experiences and attitudes of psychiatrists in their clinical practice. The aim of this study was to investigate psychiatrists' daily practice with therapeutic drug monitoring in Turkey.

METHODS

A nation-wide cross-sectional survey among adult and child psychiatry specialist psychiatrists in Turkey was conducted.

RESULTS

We found that 98.4% (n = 380) of the study participants used TDM in clinical practice and 1.6% (n = 6) did not. However, TDM use is limited to mood stabilizers (lithium 96.3%, valproate 97.6%) to a great extent. Only a small number of psychiatrists perform TDM for other psychotropic drugs, e.g., clozapine 2.4%, tricyclic antidepressants 1.3%, benzodiazepines 1.1%, and selective serotonin reuptake inhibitors 0,8%.

CONCLUSIONS

Most of the psychiatrists in Turkey have a positive attitude toward use of therapeutic drug monitoring although there is also a considerable difficulty to reach services for the therapeutic drug monitoring of psychotropics other than mood stabilizers.

The development and validation of a turbulent flow-liquid chromatography-tandem mass spectrometric method for the simultaneous quantification of citalopram, sertraline, bupropion and hydroxybupropion in serum

OBJECTIVES

Depression is a rapidly growing issue in the United States. There are many drug classes that may be used to treat depression, including the selective serotonin-reuptake inhibitors (SSRIs) citalopram (Celexa®) and sertraline (Zoloft®), as well as the aminoketone bupropion (Wellbutrin®). However, therapeutic efficacy and treatment success is often variable, requiring changes in dosing regimens or drug selection. Methods for drug quantification can become important tools in the assessment of drug efficacy to optimize treatment regimens. Here, we present a turbulent flow-liquid chromatography-tandem mass spectrometric (TFC-MS/MS) method for the robust, simultaneous quantification of citalopram, sertraline, bupropion and its active metabolite, hydroxybupropion (OH-bupropion).

DESIGN AND METHODS

Serum spiked with the aforementioned antidepressants, along with their corresponding isotopically labeled internal standards was subjected to protein precipitation. Samples were injected onto a TFC column for on-line solid phase extraction and a Hypersil Gold C18 column for chromatographic separation. Detection was achieved using a TSQ Vantage mass spectrometer. Assay validation followed FDA bioanalytical guidelines.

RESULTS

The analytical measuring range for all analytes spanned from 5 to 1000ng/mL. Intra- and inter-assay precision across four quality control levels were ≤9.2% and ≤14.8%, respectively. A comparison to other LC-MS/MS methods resulted in a strong correlation with correlation coefficients ranging from 0.9929 to 0.9971. Carryover, stability, recovery, matrix effects, extraction and processing efficiency were also deemed acceptable in accordance with FDA recommendations.

CONCLUSIONS

The development and validation of this TFC-MS/MS method allow for the robust and high-throughput quantification of commonly prescribed antidepressants.

The influence of 5-HTTLPR genotype on the association between the plasma concentration and therapeutic effect of paroxetine in patients with major depressive disorder

INTRODUCTION

The efficacy of treatment with selective serotonin reuptake inhibitors in patients with major depressive disorder (MDD) can differ depending on the patient's serotonin transporter-linked polymorphic region (5-HTTLPR) genotype, and the effects of varying plasma concentrations of drugs can also vary. We investigated the association between the paroxetine plasma concentration and clinical response in patients with different 5-HTTLPR genotypes.

METHODS

Fifty-one patients were enrolled in this study. The Montgomery-Asberg Depression Rating Scale (MADRS) was used to evaluate patients at 0, 1, 2, 4, and 6 weeks. The patients' paroxetine plasma concentrations at week 6 were measured using high-performance liquid chromatography. Additionally, their 5-HTTLPR polymorphisms (alleles S and L) were analyzed using a polymerase chain reaction with specific primers. We divided the participants into two groups based on their L haplotype: the SS group and the SL and LL group. We performed single and multiple regression analyses to investigate the associations between MADRS improvement and paroxetine plasma concentrations or other covariates for each group.

RESULTS

There were no significant differences between the two groups with regard to demographic or clinical data. In the SS group, the paroxetine plasma concentration was significantly negatively correlated with improvement in MADRS at week 6. In the SL and LL group, the paroxetine plasma concentration was significantly positively correlated with improvement in MADRS at week 6 according to the results of the single regression analysis; however, it was not significantly correlated with improvement in MADRS at week 6 according to the results of the multiple regression analysis.

CONCLUSION

Among patients with MDD who do not respond to paroxetine, a lower plasma concentration or a lower oral dose of paroxetine might be more effective in those with the SS genotype, and a higher plasma concentration might be more effective in those with the SL or LL genotype.

The value of drug and metabolite concentration in blood as a biomarker of psychopharmacological therapy

Desirable and undesirable effects of a drug are related to its concentration at various sites of actions. For many psychotropic drugs, it has been shown that drug concentration in brain correlates with concentration in blood. The latter is also an available estimate of clearance and bioavailability. Its monitoring enables identification of multiple factors that have an impact on clinical outcomes, especially uncertain compliance and pharmacokinetic peculiarities. For this review we analysed for antidepressants if drug concentration in blood can be used as biomarker for psychopharmacological treatment. Systematic review of the literature revealed for new and old antidepressant drugs that drug and metabolite concentrations in blood are measures of the pharmacokinetic phenotype and related differentially to occupancy of primary target structures, therapeutic effects and unwanted anticholinergic, cardiac and other side effects. Drug concentration in blood can therefore be used as biomarker in clinical practice to guide psychopharmacological treatment with established antidepressant drugs. Monitoring of drug concentration is suitable to improve efficacy and safety of the pharmacotherapy, especially in elderly patients who require complex pharmacological therapies.

Therapeutic Drug Monitoring of Antidepressants and Cytochrome P450 Genotyping in General Practice

In the psychiatric setting, therapeutic drug monitoring and genotyping for cytochrome P450 (CYP) polymorphisms help to ensure and maintain therapeutic drug levels. In this study, the authors extended the therapeutic drug monitoring and genotyping protocol routinely used in their psychiatric clinic to primary care patients treated with antidepressants. They examined the variation in serum concentrations and assessed the role of CYP polymorphisms, wrong dosing, and noncompliance in deviating serum concentrations. Of 227 serum concentrations obtained, 127 (56%) were more than 20% outside therapeutic ranges. Of these 127 cases, 64 (50%) were congruous with aberrant CYP2D6 or CYP2C19 genotypes, incorrect dosing, or a pharmacy record suggesting noncompliance. Prevalence of aberrant CYP2D6 and CYP2C19 genotypes did not differ significantly between the investigated primary care patients and 751 secondary care users of antidepressants. The therapeutic drug monitoring and the genotyping findings resulted in recommendations to physicians to alter the medication strategy of 146 (64%) patients. These results strongly suggest that the rationale for therapeutic drug monitoring and CYP genotyping when prescribing antidepressants in secondary care also applies to the primary care setting.

Effects of gender and age on serum concentrations of antidepressants under naturalistic conditions

Therapeutic drug monitoring (TDM) data of antidepressant drugs are often evaluated using homogeneous samples of selected individuals without psychiatric or somatic comorbidity. These data may have limitations in transferability to everyday clinical practice. Hence, studies under naturalistic conditions are important to clarify the full clinical relevance of TDM of antidepressants. TDM analyses were retrospectively evaluated for a 3-year period from 2008 to 2010. The influence of gender and age on dose-corrected serum concentrations of antidepressants was examined in a standard clinical setting. 693 TDM analyses of amitriptyline and nortriptyline (AMI + NOR), 160 of citalopram (CIT), 152 of clomipramine and N-clomipramine (CLO + N-CLO), 272 of doxepine and N-doxepine (DOX + N-DOX), 359 of escitalopram (ESC), 198 of fluoxetine and N-fluoxetine (FLU + N-FLU), 92 of maprotiline (MAP), 888 of mirtazapine (MIR), and 77 of sertraline (SER) remained in the sample. Females had significantly higher dose-corrected serum concentrations of AMI + NOR (32 %), CIT (29 %), DOX + N-DOX (29 %), and MIR (20 %), and patients older than 60 years had significantly higher dose-corrected serum concentrations of AMI + NOR (21 %), CIT (40 %), DOX + N-DOX (48 %), MAP (46 %), MIR (24 %), and SER (67 %). Comparing the two extreme groups, females >60 years showed a remarkably higher dose-corrected serum concentration of AMI + NOR (52 %), CIT (78 %), DOX + N-DOX (86 %), and MIR (41 %) in contrast to males ≤60 years. Gender and age have a significant influence on the serum concentrations of different antidepressant drugs, and additive effects must be considered. TDM is recommended to reduce the risk of adverse effects due to supratherapeutic serum levels, also in a naturalistic clinical setting.

Inverse correlation between clinical response to paroxetine and plasma drug concentration in patients with major depressive disorders

OBJECTIVE

There are few data concerning a clear relationship between the clinical effect of paroxetine and plasma drug concentrations, although therapeutic ranges have been established for some tricyclic antidepressants.

METHODS

In this study, 120 patients with major depressive disorders were treated with 10-40 mg/day of paroxetine for 6 weeks, and a total of 89 patients completed the protocol. A clinical evaluation using the Montgomery-Asberg Depression Rating Scale (MADRS) was performed at 0, 1, 2, 4 and 6 weeks.

RESULTS

Significant correlations were found between the plasma concentrations of paroxetine and the percentage improvement in the total MADRS scores (r = -0.282, p < 0.01) and the final MADRS scores at 6 weeks (r = 0.268, p < 0.05). The conventional receiver-operating-characteristic curve showed the fraction of true positive results and false negative results for various cut-off levels of paroxetine concentration for response and remission. The thresholds for both response and remission that gave the maximal sensitivity and specificity for paroxetine concentrations were 64.2 ng/ml.

CONCLUSIONS

These results suggest that plasma paroxetine concentrations are negatively associated with improvement and that response occurs at the upper threshold of 64.2 ng/ml of paroxetine. These findings should be replicated with a larger patient sample.

Association between citalopram serum levels and clinical improvement of patients with major depression

Imaging studies have shown that serum concentrations of the selective serotonin reuptake inhibitor citalopram correlate with serotonin transporter (5-HTT) occupancy in vivo. In patients with major depressive disorders treated with citalopram, 80% 5-HTT occupancy was considered to be necessary for maximal therapeutic effects, which requires citalopram serum concentrations of at least 50 ng/mL. The aim of this study was to compare treatment outcome in patients with citalopram serum concentrations greater than and less than 50 ng/mL after 7 days of treatment. This study included inpatients with acute major depressive disorder according to International Classification of Disease, 10th Revision who were treated with citalopram. In weekly intervals, the severity of depression was assessed with the 17-item Hamilton Depression Rating Scale (HAMD-17), and serum concentrations of citalopram were measured from baseline until week 5. Fifty-five patients were eligible for this analysis. After 7 days of treatment, 19 patients showed citalopram serum concentrations of 50 ng/mL or greater; 36 patients had lower concentrations. Patients at greater than the 50-ng/mL threshold had (i) lower mean HAMD-17 sum scores from day 7 to end point (P ≤ 0.018 for each analysis); (ii) a more pronounced HAMD-17 decrease (P ≤ 0.019 for each analysis), and (iii) 23 days' shorter duration of hospitalization (P = 0.033) than patients with levels of citalopram less than 50 ng/mL. As regards adverse effects, both patient groups were not significantly different. Despite therapeutic doses, a significant number of patients had serum concentrations less than 50 ng/mL, and these were associated with an unfavorable treatment outcome; therapeutic drug monitoring is recommended to optimize dosing citalopram in the early phase of treatment.

Bio-sample preparation and analytical methods for the determination of tricyclic antidepressants

An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and different analytical methods applied for the quantification of tricyclic antidepressants. These procedures are relevant tools in clinical and forensic toxicology. It is revealed that SPE, for sample preparation, and HPLC, using reversed-phase alkyl (C18) or cyanopropyl-bonded silica columns for the analytes separation, are effective and versatile methods for assay of tricyclic antidepressants. These methods enable achievable detection limits using UV/diode array detection, readily available in most laboratories, down to 1–8 ng ml-1, and using electron capture detection better than 1 ng ml-1, which is lower than that for nitrogen–phosphorus detector. MS interfaced with electrospray ionization offered similar sensitivity, whilst sonic spray ionization provided detection down to 0.03 ng ml-1. A brief discussion on chemical structures, metabolism and mechanism of action of this group of drugs is also presented.

Frequency of laboratory monitoring of chronic medications administered to nursing facility residents: results of a national Internet-based study

OBJECTIVE

To determine the minimal frequency of laboratory monitoring of 30 types of chronic medications or classes that are administered to nursing facility residents and are either listed under pharmacy services tag F329 (the tag for unnecessary medications), or have a narrow therapeutic index.

DESIGN AND SETTING

Cross-sectional, Internet-based survey.

PARTICIPANTS

National sample of 500 pharmacists, 500 nurse practitioners, and 327 physicians.

MAIN OUTCOME MEASURE

Minimal frequency of monitoring, recorded as an interval of 1, 3, 6, 9, or 12 months, for each of 35 laboratory parameters (e.g., serum drug level, complete blood count, liver function tests) for the 30 types of chronic medications or classes. Agreement was defined as having two or more of the three professional groups select the same minimal monitoring interval.

RESULTS

Overall, 116 professionals (20 pharmacists, 48 physicians, and 48 nurse practitioners) completed the survey. Most respondents were women (58.6% [68/116]), and most had worked in nursing facilities for > 5 years (66.4% [77/116]). Regarding minimal laboratory monitoring intervals, respondents reached agreement concerning 33 of 35 parameters. They selected three or six months as the minimum interval for 30 of 35 parameters (85.7%), one month as the minimum for two parameters, and 12 months as the minimum for one parameter.

CONCLUSION

The multidisciplinary panel agreed that most medications that were listed under the F329 tag or have a narrow therapeutic index should have laboratory monitoring every three or six months. The results can be used by nursing facility professionals to establish minimal laboratory monitoring parameters for chronic medications, which may potentially reduce the occurrence of adverse drug reactions.

Therapeutic drug monitoring in neuropsychopharmacology: does it hold its promises?

To produce its characteristic effects, a drug must be present in appropriate concentrations at its sites of action. The latter is not only a function of the dose administered, but also of the extent and rate of drug absorption, distribution, tissue binding, biotransformation, and excretion, which can vary markedly between individual patients due to differences in gender, age, morbidity, smoking or eating habits, differential expression of drug metabolising enzymes or drug transporters or other factors. Therefore drug concentrations in blood resulting after a given dose differ by tenfold or more between individual patients. For psychoactive drugs, animal studies have shown that plasma concentrations of psychotropic drugs correlate well with concentrations in the target organ, the brain. In the brain of patients treated with antipsychotic or antidepressant drugs clear-cut relationships were found between plasma concentrations of the drug and occupancy of dopamine receptors or serotonin uptake sites by positron emission tomography (PET). Monitoring concentrations of psychoactive drugs in plasma of patients, so called therapeutic drug monitoring (TDM), is therefore useful to adjust dosages for optimal "receptor" blockade. TDM is well established for mood stabilizers and anticonvulsant drugs. For other neuropsychiatric drugs, however, "routine" TDM is rare. Optimal target concentrations are unclear for many drugs, and the number of laboratories that use reliable methods to measure the low concentrations of the drugs within a single day is quite limited. Moreover, the use of TDM in practice is far from optimal. The TDM group of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP see http://www.agnp.de/) has published literature-based guidelines for optimal use of TDM in psychiatry. TDM can be most informative to solve problems underlying the treatment of an individual patient. It can be clarified if suggested non-compliance or insufficient response in spite of recommended doses is due to rapid metabolism of the drug. Moreover, many drug interactions have been detected by using TDM. In conclusion, TDM is a reliable tool to optimise psychopharmacotherapy. When used adequately it is helpful for many psychiatric patients and in many situations.

Therapeutic drug monitoring of tricyclic antidepressants in everyday clinical practice

Data about therapeutic drug monitoring (TDM) of psychotropic medications are often obtained from samples of highly selected individuals, who may not be representative for the average psychiatric patient. These data therefore may have limitations with regard to their transferability to everyday clinical practice. Therefore studies under naturalistic conditions are important to clarify the full clinical relevance of TDM. We retrospectively evaluated all TDM-analyses of the tricyclic antidepressants (TCA) amitriptyline and clomipramine during a 12-month period in an unselected sample of patients in a standard clinical setting. We especially examined the relationship between serum levels on one hand and clinical response and adverse effects on the other hand. In patients with amitriptyline, responders showed a significantly higher serum level than non-responders, whereas in patients with clomipramine a serum level within the recommended therapeutic range was associated with clinical response. We also found significantly higher serum concentrations in patients with adverse effects compared to patients without adverse effects in the clomipramine group. No such relationship could be shown in patients treated with amitriptyline. Our results suggest that therapeutic ranges in naturalistic settings in some ways differ from those obtained in controlled clinical settings and that TDM studies in everyday clinical practice are necessary and beneficial.

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00-40.0 microg mL(-1)), phenobarbital (5.00-40.0 microg mL(-1)), primidone (3.00-40.0 microg mL(-1)), carbamazepine and carbamazepine-epoxide (2.00-24.0 microg mL(-1)), phenytoin (2.00-40.0 microg mL(-1)), and lamotrigine (0.50-12.0 microg mL(-1)). The antidepressants' linear plasmatic concentration ranged from 75.0 to 500 ng mL(-1) for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL(-1) for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.

Appropriateness of therapeutic drug monitoring for antidepressants in routine psychiatric inpatient care

Although there is sufficient evidence of the benefits of therapeutic drug monitoring (TDM) for optimizing antidepressant therapy, its current use in routine care is far from optimal. As a prerequisite for developing improvement strategies, the appropriateness of TDM use was investigated in a psychiatric hospital in which TDM is applied routinely to a large extent. A retrospective analysis of all patients admitted in 2003 with a unipolar depressive disorder was performed. Based on detailed chart review, for all TDM tests, the time of blood sample taking in relation to the medication process and the consequences of the TDM results for clinical decision making were analyzed. Altogether, 748 plasma levels were measured for antidepressants. The evaluation identified considerable inappropriate use of TDM. After a preceding change of dose, only the minority of TDM tests was performed within an optimum time interval. Overall, 30% of blood samples were taken too early, before steady state had been reached. The high number of repeat tests without preceding change of drug dose points to potentially redundant use. There also was evidence of underuse of TDM, as in many cases additional plasma level determinations might have been useful to speed up optimal dosing. Frequent discrepancies were found between the laboratory's recommendations and actual clinical decision making. Suggested dose changes were followed in only 30%. The findings clearly indicate the need for measures to improve the implementation of TDM in routine care. Based on the identified pattern of current TDM utilization and experiences from other fields of medicine, a combination of strategies, including both educational and electronic interventions, may have the greatest potential for improvement.

Therapeutic Drug Monitoring and Pharmacogenetic Tests as Tools in Pharmacovigilance

Therapeutic drug monitoring (TDM) and pharmacogenetic tests play a major role in minimising adverse drug reactions and enhancing optimal therapeutic response. The response to medication varies greatly between individuals, according to genetic constitution, age, sex, co-morbidities, environmental factors including diet and lifestyle (e.g. smoking and alcohol intake), and drug-related factors such as pharmacokinetic or pharmacodynamic drug-drug interactions. Most adverse drug reactions are type A reactions, i.e. plasma-level dependent, and represent one of the major causes of hospitalisation, in some cases leading to death. However, they may be avoidable to some extent if pharmacokinetic and pharmacogenetic factors are taken into consideration. This article provides a review of the literature and describes how to apply and interpret TDM and certain pharmacogenetic tests and is illustrated by case reports. An algorithm on the use of TDM and pharmacogenetic tests to help characterise adverse drug reactions is also presented. Although, in the scientific community, differences in drug response are increasingly recognised, there is an urgent need to translate this knowledge into clinical recommendations. Databases on drug-drug interactions and the impact of pharmacogenetic polymorphisms and adverse drug reaction information systems will be helpful to guide clinicians in individualised treatment choices.

The impact of Cytochrome P450-2D6 genotype on the use and interpretation of therapeutic drug monitoring in long-stay patients treated with antidepressant and antipsychotic drugs in daily psychiatric practice

PURPOSE

This retrospective follow-up study investigates whether cytochrome P450-2D6 (CYP2D6) genotype explains variability in plasma concentrations of psychotropic drugs in daily psychiatric practice.

METHODS

The study population consisted of 62 hospitalised psychiatric patients genotyped for CYP2D6. Primary endpoint was the normalised plasma concentration ratio which was defined as the [measured concentration]/[mean therapeutic concentration] allowing comparison of plasma concentrations of different substrates. Secondary endpoint was a plasma concentration above the therapeutic range. The determinant was CYP2D6 genotype classified as ultrarapid metaboliser (UM), extensive metaboliser (EM), intermediate metaboliser (IM), or poor metaboliser (PM). The relation between CYP2D6 genotype and the normalised plasma concentration ratio was assessed with a linear mixed-effects model after adjustment for the Prescribed Daily Dose (PDD). The risk of having a plasma concentration above the therapeutic range was assessed with a logistic mixed-effects model.

RESULTS

For antidepressants, CYP2D6 genotype PM (1.68 (95%CI: 1.01-2.28)) and IM (1.09 (95%CI: 0.77-1.29)) were associated with higher normalised plasma concentration ratios of antidepressants compared to EMs (0.56 (95%CI: 0.26-0.74)). In addition, the risk of a plasma concentration above the therapeutic range was increased for PMs (OR 33.1 (95%CI: 2.0-544.6)) and IMs (OR 8.2 (95%CI: 1.1-60.3)) relative to EMs using antidepressants. CYP2D6 genotype could not clearly explain variability in plasma concentrations of antipsychotics possibly due to a low frequency of therapeutic drug monitoring (TDM) in antipsychotics primarily metabolised by CYP2D6 in daily psychiatric practice.

CONCLUSIONS

CYP2D6 genotype contributes to clinically relevant variability in plasma concentrations of antidepressants but probably not antipsychotics in daily clinical practice.

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.

Impact of the CYP2D6 ultra-rapid metabolizer genotype on doxepin pharmacokinetics and serotonin in platelets

INTRODUCTION

CYP2D6 gene duplication causing ultrafast metabolism is one reason for failure in responding to CYP2D6-metabolized antidepressants. We studied the effect of the CYP2D6 duplication genotype on doxepin pharmacokinetics and platelet serotonin uptake and concentrations.

METHODS

Pharmacokinetics of trans (E)- and cis (Z)-doxepin and N-desmethyldoxepin were analyzed after a single dose of 75 mg doxepin in 11 ultrafast metabolizers (UM), 11 extensive metabolizers (EM) and 3 poor metabolizers (PM), identified by genotyping for CYP2D6 alleles *2, *3, *4, *5, *6, *9, *10, *35, *41 and specific analyses to characterize gene duplication. Platelet serotonin concentrations were measured by HPLC.

RESULTS

A trend for lower AUC of the active principle (sum of doxepin and N-desmethyldoxepin) in UMs versus EMs was detected (575 versus 1,000 nmol h/l, P=0.07), mainly due to the differences in desmethyldoxepin concentrations (P=0.003). Stereoselective analysis showed a significant effect of the UM genotype on (E)-doxepin pharmacokinetic parameters whereas those of (Z)-doxepin did not differ between the CYP2D6 genotype groups. The 75-mg doxepin dose had no effect on platelet serotonin concentration and uptake, but serotonin concentrations in platelets were significantly higher in UM in comparison to the EM and PM groups. At baseline, these concentrations were 462, 399, and 292 ng/10 platelets in UM, EM and PM (P<0.0001 for trend).

CONCLUSIONS

At the same dose, internal exposure to doxepin differed by more than ten-fold between the CYP2D6 genotype groups. CYP2D6 may have an effect on platelet serotonin explained by salvage pathways of 5-methoxytryptamine to serotonin mediated by CYP2D6; however, this finding requires further confirmatory experiments.

The safety of SSRIs in generalised anxiety disorder: any reason to be anxious?

Generalised anxiety disorder (GAD) significantly impacts upon quality of life and has a chronic and persistent nature. GAD requires pharmacological therapies that are well-tolerated, lessen the mitigating effects of common comorbidities and do not pose a high risk for dependency or abuse. Selective serotonin and serotonin-noradrenaline re-uptake inhibitors have become more viable treatments for GAD than the traditionally used benzodiazepines due to greater efficacy and a more tolerable adverse event profile. Among these newer-generation antidepressants, only paroxetine and venlafaxine are currently FDA-approved for the treatment of GAD. Paroxetine was approved after three double-blind, placebo-controlled studies demonstrated its superior efficacy compared to placebo for short-term treatment of GAD. Venlafaxine was approved for both short- and long-term treatment of GAD after demonstrating efficacy in 8-week and 6-month double-blind, placebo-controlled trials. For both paroxetine and venlafaxine, the safety and tolerability profiles during treatment of GAD are consistent with those demonstrated during the short- and long-term treatment of patients with major depressive disorder.