Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: focus on antipsychotics.

BACKGROUND: For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialized tools are used. Three tools have been proven useful to personalize drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging. METHODS: In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 50 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)). RESULTS: Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings. CONCLUSION: All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimize treatment effects, minimize side effects and ultimately reduce the global burden of diseases, personalized drug treatment has not yet become the standard of care in psychiatry.

Tools for optimising pharmacotherapy in psychiatry (therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests): focus on antidepressants.

Objectives: More than 40 drugs are available to treat affective disorders. Individual selection of the optimal drug and dose is required to attain the highest possible efficacy and acceptable tolerability for every patient.Methods: This review, which includes more than 500 articles selected by 30 experts, combines relevant knowledge on studies investigating the pharmacokinetics, pharmacodynamics and pharmacogenetics of 33 antidepressant drugs and of 4 drugs approved for augmentation in cases of insufficient response to antidepressant monotherapy. Such studies typically measure drug concentrations in blood (i.e. therapeutic drug monitoring) and genotype relevant genetic polymorphisms of enzymes, transporters or receptors involved in drug metabolism or mechanism of action. Imaging studies, primarily positron emission tomography that relates drug concentrations in blood and radioligand binding, are considered to quantify target structure occupancy by the antidepressant drugs in vivo. Results: Evidence is given that in vivo imaging, therapeutic drug monitoring and genotyping and/or phenotyping of drug metabolising enzymes should be an integral part in the development of any new antidepressant drug.Conclusions: To guide antidepressant drug therapy in everyday practice, there are multiple indications such as uncertain adherence, polypharmacy, nonresponse and/or adverse reactions under therapeutically recommended doses, where therapeutic drug monitoring and cytochrome P450 genotyping and/or phenotyping should be applied as valid tools of precision medicine.

Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2017.

Therapeutic drug monitoring (TDM) is the quantification and interpretation of drug concentrations in blood to optimize pharmacotherapy. It considers the interindividual variability of pharmacokinetics and thus enables personalized pharmacotherapy. In psychiatry and neurology, patient populations that may particularly benefit from TDM are children and adolescents, pregnant women, elderly patients, individuals with intellectual disabilities, patients with substance abuse disorders, forensic psychiatric patients or patients with known or suspected pharmacokinetic abnormalities. Non-response at therapeutic doses, uncertain drug adherence, suboptimal tolerability, or pharmacokinetic drug-drug interactions are typical indications for TDM. However, the potential benefits of TDM to optimize pharmacotherapy can only be obtained if the method is adequately integrated in the clinical treatment process. To supply treating physicians and laboratories with valid information on TDM, the TDM task force of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) issued their first guidelines for TDM in psychiatry in 2004. After an update in 2011, it was time for the next update. Following the new guidelines holds the potential to improve neuropsychopharmacotherapy, accelerate the recovery of many patients, and reduce health care costs.

Neither mycophenolate acyl-glucuronide levels nor their areas under the curve are responsible for the gastrointestinal side effects in kidney transplant recipients receiving EC-MPA: a prospective trial.

INTRODUCTION: Since previous in vitro studies suspected the metabolite mycophenolate acyl-glucuronide (AcMPAG) to be responsible for the gastrointestinal side effects, we examined the correlation between AcMPAG blood levels and patient gastrointestinal satisfaction inquiries using a standardized, validated questionnaire. PATIENTS AND METHODS: We enrolled 63 renal transplant patients, however, two discontinued the study and 16 were excluded because of inadequate completion of the questionnaires or missing blood values or discontinuation of enteric coated mycophenolic acid (EC-MPA) therapy, severe side effects or viral infections. The final responses of 45 people were subjects to statistical analysis. Gastrointestinal side effects were examined using the Gastrointestinal Symptom Rating Scale (GSRS) completed at three times: T1 (3-5 days after transplantation), T2 (10-15 days), and T3 (3 months). The GSRS results generated two groups of patients based on cutoff values set at a score of 4 points for each item. Scores less than 4 were assumed to be "no side effects"; ≥4, "side effects." AcMPAG was measured by mass spectroscopy on blood samples obtained at fixed times generating three pharmacokinetic profiles per patient. RESULTS: There was no relation between high AcMPAG blood concentrations and gastrointestinal dissatisfaction. Neither Ac-MPAG area under the curve (AUC) in the absorption phase nor AcMPAG peak values correlated with gastrointestinal dissatisfaction. CONCLUSION: There was no significant correlation between mean AcMPAG and GSRS scores, although previous studies had suggested AcMPAG maximum values or alternatively AcMPAG AUC in the absorption phase to relate to side effects.

Pharmacogenetics and olanzapine treatment: CYP1A2*1F and serotonergic polymorphisms influence therapeutic outcome.

Psychiatric pharmacotherapy with olanzapine is commonplace. We investigated the influence of CYP1A2*1F (-163A, rs762551) and serotonergic polymorphisms on olanzapine serum concentrations and clinical outcome in a naturalistic clinical setting. Included were 124 Caucasian psychiatric inpatients treated with olanzapine for at least 4 weeks with steady-state serum concentrations available for 73 patients. The CYP1A2*1F polymorphism was reported to affect the inducibility of CYP1A2. In our study population, CYP1A2*1F/*1F genotype alone resulted in a 22% reduction of dose-/body weight-normalized olanzapine serum concentrations compared to homo- and heterozygote carriers of CYP1A2*1A (both groups without inducers). This effect was independent of the well-known effect of inducing agents (here tobacco smoke and carbamazepine which led to on average 28% lower concentrations in CYP1A2*1A carriers and 26% lower concentrations in CYP1A2*1F/*1F carriers). Consistently, patients with the CYP1A2*1F/*1F genotype taking inducers had 22% lower concentrations compared to CYP1A2*1A carriers taking inducers. The influence of genotype alone remained significant after Bonferroni's post hoc test. Higher olanzapine concentrations were significantly correlated with better improvement of paranoid and depressive symptoms in patients with schizophrenic disorders (Spearman's r=0.5, P=0.026 and P=0.006, respectively). No relationship between serum concentrations and the side effects (DOTES) score was detected. However, patients with the 5-HTR2A intron 2 (rs7997012) AA genotype suffered from more pronounced side effects compared to carriers of the GA or GG genotype (P=0.018 and P=0.002). Short-term weight gain under olanzapine therapy was significantly lower for 5-HTR2C -759 T-allele carriers (P=0.011). Our data suggest that the CYP1A2*1F/*1F genotype exhibits a significant influence on olanzapine concentrations independent of other inducing factors. Thus, CYP1A2*1F genotyping may be useful for clinical treatment decisions given the fact that olanzapine serum concentrations correlated with treatment response. Side effects and weight gain, however, seem to be more influenced by serotonergic polymorphisms.

Intermediate metabolizer: increased side effects in psychoactive drug therapy. The key to cost-effectiveness of pretreatment CYP2D6 screening?

The cytochrome P450 2D6 (CYP2D6) isoenzyme metabolizes about 25% of clinically used drugs. The impact of CYP2D6 metabolizer status on therapeutic outcome was assessed in 365 psychiatric in-patients treated with neuroleptics or antidepressants. Length of hospitalization and response onset were prolonged for patients receiving CYP2D6 drugs. Intermediate metabolizers (IMs) receiving CYP2D6 doses above the population median had more side effects after 4 weeks than extensive metabolizers with above-median doses (9/13, 69% vs 4/23, 17%, P = 0.003), than IMs with below-median doses (5/22, 23%, P = 0.012) and IMs with other medication (24/84, 29%, P = 0.009). The Clinical Global Impression scale response was lower for IMs treated with CYP2D6 drugs (3/42, 7%) than for IMs with other medication (21/84, 25%, P = 0.017) probably due to increased side effects. Identification of IM status (38% of study population) may help to reduce side effects and length/cost of hospitalization. Thus, not only poor and ultrarapid metabolizer but also IMs may benefit from CYP2D6 genotyping. This is of paramount interest since it greatly improves cost/benefit estimations for pretreatment CYP2D6 screening.

DRD4 48 bp VNTR but not 5-HT 2C Cys23Ser receptor polymorphism is related to antipsychotic-induced weight gain.

Weight gain is a major side effect of antipsychotic treatment. The antidopaminergic and antiserotonergic effect of antipsychotics may contribute to antipsychotic-induced weight gain. We, therefore conducted a prospective clinical study, to investigate whether the D4 receptor (DRD4) 48 bp (base pair) variable number of tandem repeat (VNTR) polymorphism and the 5-hydroxytryptamine 2C receptor (HT(2C)) cysteine for serine substitution at position 23 (Cys23Ser) polymorphism may influence weight gain during antipsychotic treatment in a naturalistic setting of 102 Caucasian psychiatric in-patients. Patients suffering from psychotic disorders and treated according to local clinical practice were classified as either homozygous for the shorter alleles of the DRD4 48 bp VNTR polymorphism (<7-fold repeat, group 1) or heterozygous/homozygous for the long allele (7-fold repeat or higher, group 2). HT(2C) Cys23Ser polymorphism male patients were grouped hemizygous G (Cys) or C (Ser), while female patients were GG, GC or CC and both sexes were evaluated separately. Concerning the DRD4 48 bp VNTR polymorphism the increase in body mass index was significantly less in group 1 (0.38 kg m(-2); s.d.=1.04) than in group 2 (0.89 kg m(-2); s.d.=1.23; P=0.003). The difference between the genotype groups remained significant in male patients but not in female patients. In contrast, no influence on antipsychotic-induced increase in body weight was observed for the HT(2C) Cys23Ser polymorphism. These results support the hypothesis that the DRD4 48 bp VNTR polymorphism influences antipsychotic-induced weight gain. Male patients may be more affected than female patients. Due to the limitations of the study (heterogeneity of treatment, pretreatment and concomitant therapy) further studies are required before diagnostic genotyping of the DRD4 48 bp VNTR polymorphism may be useful for individualizing therapy.

Doxepin plasma concentrations: is there really a therapeutic range?

Despite the introduction of numerous new agents, tricyclic antidepressants remain an important option for the treatment of depression. Doxepin is still in wide use, and determining its concentration is a standard procedure in many psychiatric clinics. Some widely cited reviews indicate a therapeutic range from 150 to 250 ng/mL (parent plus desmethyl metabolite). The vast majority of the authors' patients fell short of these concentrations under customary doses. To resolve this issue, the authors' serum-level databank was analyzed, a questionnaire was sent to U.S. and German psychiatric university departments and laboratories, and the literature was reviewed. The main results were the following: (1) Only 9% of all samples analyzed (N = 217) displayed plasma levels (high-performance liquid chromatography) between 150 and 250 ng/mL; 88% were subtherapeutic. The mean doxepin + desmethyldoxepin steady-state serum concentration was 89+/-75 ng/mL (N = 32, doxepin >3 weeks). The mean daily dose was 143+/-30 mg. There was no correlation between concentrations and improvement. (2) A wide variety of recommendations is given by the different university departments (10-1,000 ng/mL). (3) According to the studies published to date, there is not enough evidence for recommending a therapeutic range. The preliminary suggestions given in some influential reviews have been widely adopted without critical re-evaluation. Compared with the concentrations found in the original studies, the therapeutic ranges suggested are too high. A methodologically sound study to determine a therapeutic range is required for the rational monitoring of this drug. Meanwhile, a preliminary working range of 50 to 250 ng/mL is proposed on the basis of critical reassessment of published data.

Pharmacogenetics: a new diagnostic tool in the management of antidepressive drug therapy.

Pharmacogenetics studies the genetic basis of an individual's ability to respond to pharmacotherapy. Variability of this response is a major problem. Fatal adverse drug reactions have been reported to be the fourth leading cause of death in the US. In depression, 30-40% of all patients do not respond sufficiently to the initial treatment and it can take up to 6 weeks for them to be identified. Much knowledge has been gathered throughout the last 3 decades about the genetic basis of pharmacokinetic variability. Genetic tests suitable for the routine laboratory are now available for some important metabolizing enzymes (e.g., CYP2D6, CYP2C19) identifying those individuals who are slow or fast metabolizers of certain drugs, many of which are widely used in the treatment of depression (e.g., tricyclic antidepressants). The possible use of these tests in the clinical practice of monitoring antidepressant therapy is discussed in relation to older phenotyping methods and therapeutic drug monitoring.Less well studied than the genetics of pharmacokinetics is the genetic basis of pharmacodynamic variability. As selective serotonin reuptake inhibitors (SSRI) have a wide therapeutic index, pharmacokinetic variability usually does not explain insufficient response to therapy. Recently, some excitement was caused by reports on serotonin transporter gene polymorphisms and their influence on the response to antidepressive therapy with SSRIs as this could provide an interesting diagnostic tool in assessing the chances of response to the most popular group of antidepressants at present. Current knowledge in this young field of research is summarized.

Effect of adjunctive paroxetine on serum levels and side-effects of tricyclic antidepressants in depressive inpatients.

RATIONALE: Previous studies showed that adjunctive paroxetine increases tricyclic antidepressant (TCA) serum levels by inhibiting cytochrome P4502D6. This effect has, however, been examined only in experimental studies using low doses of TCAs in healthy volunteers. OBJECTIVE: The present study investigated TCA serum level changes and side-effects after the addition of paroxetine in depressed patients treated with doses customarily used for inpatients. METHODS: 14 patients who had a moderate or severe depressive episode according to ICD-10 and who had not sufficiently responded (< or = 25% reduction of the Hamilton depression scale) to 3-week monotherapy with amitriptyline (n = 9) or imipramine (n = 5) with daily doses between 125 and 200 mg/day, received 20 mg/day paroxetine additionally under steady state conditions. RESULTS: After 2 weeks the serum levels of the metabolites nortriptyline (from 88 +/- 49 ng/ml to 176 +/- 57 ng/ml) and desipramine (from 152 +/- 78 ng/ml to 338 +/- 104 ng/ml) had risen to a significantly greater extent than those of the parent compounds amitriptyline (123 +/- 50 ng/ml to 195 +/- 128 ng/ml) and imipramine (from 75 +/- 36 ng/ml to 98 +/- 51 ng/ml). It is noteworthy that, with the exception of one case of incipient delirium, the combination therapy was well tolerated despite high TCA serum level rises. CONCLUSION: The higher increase of the metabolites as compared with the parent compounds can be explained by a paroxetine-induced inhibition of the liver enzyme cytochrome P4502D6, which catalyses the second step of the TCA metabolism, i.e. the hydroxylation of the metabolites. Blood levels should be meticulously monitored, if TCAs are combined with paroxetine.

Intoxication due to negative canrenone interference in digoxin drug monitoring.

Canrenone and spironolactone caused falsely low readings in a common assay for digoxin (AxSym MEIA) due to negative cross-reactivity. Misleading subtarget concentrations were repeatedly reported, and falsely guided drug dosing resulted in a case of digoxin intoxication.

Performance and specificity of monoclonal immunoassays for cyclosporine monitoring: how specific is specific?

BACKGROUND: Immunoassays designed for the selective measurement of cyclosporin A (CsA) inadvertently show cross-reactivity for CsA metabolites. The extent and clinical significance of the resulting overestimation is controversial. A comprehensive assessment of old and new methods in clinical specimens is needed. METHODS: In a comprehensive evaluation, CsA was analyzed in 145 samples with the new CEDIA assay and compared with the Emit assay with the old and new pretreatments, the TDx monoclonal and polyclonal assays, the AxSYM, and HPLC. All samples were from patients with liver and/or kidney transplants. RESULTS: The CEDIA offered the easiest handling, followed by the AxSYM, which showed the longest calibration stability. The TDx monoclonal assay provided the lowest detection limit and the lowest CVs. The mean differences compared with HPLC were as follows: Emit, 9-12%; CEDIA, 18%; AxSYM, 29%; and TDx monoclonal, 57%. The CycloTrac RIA paralleled the Emit results. In contrast to the mean differences, substantial (>200%) and variable overestimations of the CsA concentration were observed in individual patient samples. Metabolic ratios, estimates of the overall concentrations of several cross-reacting metabolites (nonspecific TDx polyclonal/specific reference method), correlated with the apparent biases of the various monoclonal assays. Metabolic ratios varied up to 10-fold, which translated into biases for individual samples between -7% and +174%. The higher the cross-reactivity of an assay was, the higher was the range of biases observed. The interindividual differences markedly exceeded other factors of influence (organ transplanted, hepatic function). CONCLUSION: Because assay bias cannot be predicted in individual samples, substantially erratic CsA dosing can result. The specificity of CsA assays for parent CsA remains a major concern.

[Influence of anatomical variations of the pancreatic artery on the surgical technic of segmental pancreas transplantation in dogs]. / Einfluss der anatomischen Variationen der Arteria pancreatica auf die chirurgische Technik der segmentalen Pankreastransplantation beim Hund.

The surgical technique in clinical pancreas transplantation is still not standardized. Animal experimentation should allow a reproducible and reliable model by choosing the cervical region in dogs as the site of segmental grafting. A goal of the experiments was to determine the influence of preservation, operation technique, duct occlusion, immunosuppression, and gastrointestinal hormones (Somatostatin, Cyclosporin A). 50 grafts have been transplanted. It could be clearly demonstrated that in 54% the vascularization of the left lobe of the canine pancreas differs extremely from man. Successful results are to expect being aware of the anatomical variations. The varieties of the arterial blood supply indicate which technique has to be performed to avoid ischemic grafts due to inadequate preservation.