Concentrations of psychoactive substances in blood samples from non-fatal and fatal opioid overdoses.

AIM: The primary aim was to compare concentrations of psychoactive substances in blood in non-fatal and fatal opioid overdoses. The secondary aim was to assess the concentration levels of naloxone in blood in non-fatal overdoses and the association between naloxone findings and concomitantly detected drugs. METHOD DESIGN: Case-control study. SETTING: Norway. Fatal overdoses from 2017 and non-fatal overdoses from February 2018 to September 2019. CASES: Thirty-one non-fatal and 160 fatal opioid overdose cases. Data from the non-fatal overdoses were collected from hospital records and blood samples, and data from the fatal overdoses were collected from autopsy reports. Concentrations of psychoactive substances (including ethanol) in blood samples were collected at the time of hospital admission for the non-fatal overdoses and during autopsy for the fatal overdoses. RESULTS: The median number of different substances detected was four for fatal and five for non-fatal overdoses. The fatal overdoses had higher pooled concentrations of opioids (188 vs 57.2 ng/mL, P < .001), benzodiazepines (5467 vs 2051 ng/mL, P = .005) and amphetamines (581 vs 121 ng/mL, P < .001) than the non-fatal overdoses. A linear relationship between naloxone and concomitant pooled opioid concentrations was found (95% confidence interval = 0.002-0.135, P < .05). CONCLUSION: The total load of drug concentrations was associated with the fatal outcome of an overdose, while the number of drugs used, to a lesser extent, differentiated between those who survived and those who died from an overdose. Higher opioid concentrations were associated with treatment with higher naloxone doses.

Lithium use during breastfeeding was safe in healthy full-term infants under strict monitoring.

AIM: Previous studies on breastfeeding during lithium therapy have shown conflicting results. The aim of this study was to evaluate the safety when practising thorough follow-up of the infants. METHOD: This retrospective study focused on women with lithium medication, and their breastfed infants born between 2006 and 2021 in Stockholm, Sweden. Information about infant serum lithium concentrations and clinical status was collected from medical records. RESULTS: In total, 30 infants exposed to lithium through breastmilk, 21 girls and 9 boys, were included. The median age at follow-up was 40 days (range 8-364 days). The median lithium serum concentration was 0.10 mmol/L in the second week of life (range <0.05-0.7 mmol/L), 0.08 in week 2-4 (range <0.05-1.2), 0.06 in the second month of life (range <0.05-0.2) and 0.07 after 2 months of age (range <0.05-0.2). Unexpectedly high lithium concentrations were found in two infants in the first month of life. Apart from poor weight gain, no adverse effects were found. CONCLUSION: Serum lithium concentrations in breastfed infants were stabilised at barely measurable levels after the first weeks of life. Before that, concentrations higher than the mothers were found. Lithium treatment during breastfeeding can be considered safe under strict follow-up.

Subtherapeutic Rifampicin Concentration Is Associated With Unfavorable Tuberculosis Treatment Outcomes.

BACKGROUND: The relationships between first-line drug concentrations and clinically important outcomes among patients with tuberculosis (TB) remain poorly understood. METHODS: We enrolled a prospective cohort of patients with new pulmonary TB receiving thrice-weekly treatment in India. The maximum plasma concentration of each drug was determined at months 1 and 5 using blood samples drawn 2 hours postdose. Subtherapeutic cutoffs were: rifampicin <8 µg/mL, isoniazid <3 µg/mL, and pyrazinamide <20 µg/mL. Factors associated with lower log-transformed drug concentrations, unfavorable outcomes (composite of treatment failure, all-cause mortality, and recurrence), and individual outcomes were examined using Poisson regression models. RESULTS: Among 404 participants, rifampicin, isoniazid, and pyrazinamide concentrations were subtherapeutic in 85%, 29%, and 13%, respectively, at month 1 (with similar results for rifampicin and isoniazid at month 5). Rifampicin concentrations were lower with human immunodeficiency virus coinfection (median, 1.6 vs 4.6 µg/mL; P = .015). Unfavorable outcome was observed in 19%; a 1-µg/mL decrease in rifampicin concentration was independently associated with unfavorable outcome (adjusted incidence rate ratio [aIRR], 1.21 [95% confidence interval {CI}, 1.01-1.47]) and treatment failure (aIRR, 1.16 [95% CI, 1.05-1.28]). A 1-µg/mL decrease in pyrazinamide concentration was associated with recurrence (aIRR, 1.05 [95% CI, 1.01-1.11]). CONCLUSIONS: Rifampicin concentrations were subtherapeutic in most Indian patients taking a thrice-weekly TB regimen, and low rifampicin and pyrazinamide concentrations were associated with poor outcomes. Higher or more frequent dosing is needed to improve TB treatment outcomes in India.

Lessons from isavuconazole therapeutic drug monitoring at a United Kingdom Reference Center.

We determined isavuconazole serum concentrations for 150 UK patients receiving standard isavuconazole dosing regimens, including serial therapeutic drug monitoring for several patients on prolonged therapy. Mean trough isavuconazole concentrations in these patients were virtually identical to those reported previously from clinical trials, although greater variability was seen in patients below 18 years of age. Serial monitoring in patients receiving prolonged therapy suggested gradual, near-linear accumulation of the drug over many weeks.

Social Support Mitigates Negative Impact of Food Insecurity on Antiretroviral Adherence Among Postpartum Women in Western Kenya.

Food insecurity (FI), low social support, and low health-related quality of life (HRQoL) are associated with self-reported nonadherence to antiretroviral therapy (ART) among postpartum women, but these relationships have not been evaluated using objective adherence indicators. Hair samples were therefore analyzed among 83 postpartum Kenyan women living with HIV on efavirenz and nevirapine ART drug regimens in an observational cohort (NCT02974972). FI (0-27), social support (0-40), and HRQoL (8-40) in the prior month were also assessed. In multivariable models, each point increase in FI and decrease in HRQoL were associated with a 45.1% (95% CI: -64.3%, -15.6%) and 10.5% decrease (95% CI: 1.0%, 22.1%) in hair ART drug concentrations respectively, when social support was held constant. A significant interaction between social support and FI (ß = 0.02, p = 0.017) indicated that greater social support was predicted to mitigate the negative impacts of FI on ART adherence. Addressing these modifiable barriers could improve ART adherence during this critical period.

Moving Antiretroviral Adherence Assessments to the Modern Era: Correlations Among Three Novel Measures of Adherence.

There is no gold standard for estimating antiretroviral therapy (ART) adherence. Feasible, acceptable, and objective measures that are cost- and time-effective are needed. US adults (N = 93) on ART for ≥ 3 months, having access to a mobile phone and internet, and willing to mail in self-collected hair samples, were recruited into a pilot study of remote adherence data collection methods. We examined the correlation of self-reported adherence and three objective remotely collected adherence measures: text-messaged photographs of pharmacy refill dates for pharmacy-refill-based adherence, text-messaged photographs of pills for pill-count-based adherence, and assays of home-collected hair samples for pharmacologic-based adherence. All measures were positively correlated. The strongest correlation was between pill-count- and pharmacy-refill-based adherence (r = 0.68; p < 0.001), and the weakest correlation was between self-reported adherence and hair drug concentrations (r = 0.14, p = 0.34). The three measures provide objective adherence data, are easy to collect, and are viable candidates for future HIV treatment and prevention research.

Design of novel tacrolimus formulations with chemically synthesized oils for oral lymphatic delivery.

High consumption of oil formulations has been reported to reduce the blood exposure of drugs like tacrolimus. Consumption of oil formulations has also been shown to inhibit T-cell production of interleukin-2 (IL-2) compared to solid dispersion formulations (SDFs). However, a large amount of oil causes gastrointestinal side effects such as diarrhea and low compliance. Here, we investigated the feasibility of reducing the amount of oil and substitution of chemically synthetized oils for natural oils in these formulations. Reducing the amount of sunflower oil increased blood tacrolimus exposure despite sufficient suppression of IL-2 production. While medium-chain triglyceride (MCT) increased tacrolimus blood exposure, addition of 10% glyceryl monostearate (GMS) to MCT significantly decreased drug blood exposure without requiring a large amount of oil (p < .05). Effects of the contents of GMS in the MCT/GMS formulations, and fatty acid composition in GMS on drug blood exposure were also investigated. The results indicated that both the amount and type of oil were important for maintaining a good balance between a reduction in blood exposure and sufficient IL-2 suppression. The ratio of drug concentration in lymphocytes to that in whole blood after dosing with an oil formulation was significantly higher than that after administration of the SDF (p < .01). These results indicate the feasibility of developing oral oil tacrolimus formulations to reduce systemic side effects and maintain high efficacy for practical use in patients.

Therapeutic Drug Monitoring of Antidepressants.

For a number of antidepressants in current clinical use, concentrations in serum or plasma are a more reliable index of target drug concentrations than is dosage. For such drugs, therapeutic drug monitoring (TDM) may be a useful clinical guide for the purpose of maximizing the likelihood of favorable therapeutic outcome while minimizing the probability of clinical ineffectiveness or adverse side effects. TDM is of greatest benefit when a therapeutic range of serum concentrations has been well established. Even if such a range is not definitively determined, TDM can be of help in situations in which patients are refractory to therapy despite adequate or high dosages, when adverse events supervene even with low doses, or when noncompliance with the intended dosage plan is suspected. Serum antidepressant concentrations from TDM should be interpreted in the full context of the patient's demographic characteristics and clinical status, along with an understanding of the pharmacokinetics of the medication being taken, the timing of the sample in relation to the dosage regimen, and the specific laboratory assay procedure. TDM measurements may be costly, and the potential benefits of the information need to be weighed against the cost to the patient or to the health care system.

Intrapatient variability in plasma rifampicin & isoniazid in tuberculosis patients.

Background & objectives: Large variability in anti-tuberculosis (TB) drug concentrations between patients is known to exist. However, limited information is available on intrapatient drug levels during the course of anti-TB treatment (ATT). This study was conducted to evaluate intrapatient variability in plasma rifampicin (RMP) and isoniazid (INH) concentrations during ATT at start of the treatment, at the end of intensive phase (IP) of ATT and at the end of ATT in adult TB patients being treated in the Revised National TB Control Programme (RNTCP). Methods: Adult TB patients (n=485), receiving thrice-weekly ATT in the RNTCP, were studied. Two-hour post-dosing concentrations of RMP and INH were determined at month 1, end of IP and end of ATT, after directly observed drug administration. Drug concentrations were estimated by high-performance liquid chromatography. Results: The median (inter-quartile range) RMP concentrations during the first month, at end of IP and end of ATT were 2.1 (0.4-5.0), 2.4 (0.6-5.5) and 2.2 (0.5-5.3) µg/ml, respectively. The corresponding INH concentrations were 7.1 (4.2-9.9), 7.2 (3.9-10.9) and 6.7 (3.9-9.5) µg/ml. None of the differences in drug concentrations obtained at different time points during ATT were significant. RMP and INH concentrations at different time points were significantly correlated. Age and body mass index caused significant variability in drug concentrations. Interpretation & conclusions: Plasma RMP and INH estimations in adult TB patients at two hours after drug administration remained unaltered during ATT. Clinicians can consider testing drug concentrations at any time point during ATT. These findings may assume significance in the context of therapeutic drug monitoring of anti-TB drug concentrations.

The "Ice" Storm: Problems with Expert Evidence on the Effects of Methamphetamine.

There is growing community concern that methamphetamine (commonly known as Ice) is fuelling violent, erratic and criminal behaviour. Criminal prosecutions of Ice-fuelled defendants are on the rise. Scientific and medical expert evidence is being called upon in such criminal trials, to present the results of the defendant's blood-drug concentration and provide an opinion as to the effects of Ice on the defendant at the time of the alleged crime. Based on an analysis of recent case law and a summary of what science knows about the issue, the authors contend that any expert opinion about an accused person's likely behaviour, based on interpretations of blood-drug concentrations, are speculative and potentially prejudicial to the defendant. Such opinions should therefore be inadmissible. The authors argue for the introduction of a statutory reliability test as a way of ensuring that this unreliable expert evidence does not result in any miscarriages of justice.

Anti-tuberculosis drug concentrations in tuberculosis patients with and without diabetes mellitus.

PURPOSE: The aim of the study was to compare plasma concentrations of rifampicin (RMP), isoniazid (INH) and pyrazinamide (PZA) between tuberculosis (TB) patients with and without diabetes mellitus (DM). METHODS: Two-hour post-dosing concentrations of RMP, INH and PZA were determined in adult TB patients that were studied with (n = 452) and without DM (n = 1460), treated with a thrice-weekly regimen in India. Drug concentrations were estimated by HPLC. RESULTS: The median (IQR) INH [6.6 (3.9-10.0) and 7.8 (4.6-11.3)] and PZA [31.0 (22.3-38.0) and 34.1 (24.6-42.7)] microgram per milliliter concentrations were significantly lower in diabetic than non-diabetic TB patients (p < 0.001 for both drugs). Blood glucose was negatively correlated with plasma INH (r = -0.09, p < 0.001) and PZA (r = -0.092, p < 0.001). Multiple linear regression analysis showed RMP, INH and PZA concentrations were influenced by age and drug doses, INH and PZA by DM, RMP by alcohol use and PZA by gender and category of ATT. DM reduced INH and PZA concentrations by 0.8 and 3.0 µg/ml, respectively. CONCLUSIONS: TB patients with DM had lower INH and PZA concentrations. Negative correlation between blood glucose and drug concentrations suggests delayed absorption/faster elimination of INH and PZA in the presence of elevated glucose.

A Mathematical Model of Granulopoiesis Incorporating the Negative Feedback Dynamics and Kinetics of G-CSF/Neutrophil Binding and Internalization.

We develop a physiological model of granulopoiesis which includes explicit modelling of the kinetics of the cytokine granulocyte colony-stimulating factor (G-CSF) incorporating both the freely circulating concentration and the concentration of the cytokine bound to mature neutrophils. G-CSF concentrations are used to directly regulate neutrophil production, with the rate of differentiation of stem cells to neutrophil precursors, the effective proliferation rate in mitosis, the maturation time, and the release rate from the mature marrow reservoir into circulation all dependent on the level of G-CSF in the system. The dependence of the maturation time on the cytokine concentration introduces a state-dependent delay into our differential equation model, and we show how this is derived from an age-structured partial differential equation model of the mitosis and maturation and also detail the derivation of the rest of our model. The model and its estimated parameters are shown to successfully predict the neutrophil and G-CSF responses to a variety of treatment scenarios, including the combined administration of chemotherapy and exogenous G-CSF. This concomitant treatment was reproduced without any additional fitting to characterize drug-drug interactions.

A multisystem investigation of raltegravir association with intestinal tissue: implications for pre-exposure prophylaxis and eradication.

OBJECTIVES: Recent clinical data have suggested high raltegravir concentrations in gut tissue after oral administration, with implications for treatment and prevention. We have used in silico, in vitro, ex vivo and in vivo models to further investigate the accumulation of raltegravir in gut tissue. METHODS: Affinity of raltegravir for gut tissue was assessed in silico (Poulin-Theil method), in vitro (Caco-2 accumulation) and ex vivo (rat intestine) and compared with the lipophilic drug lopinavir. Finally, raltegravir concentrations in plasma, gut contents, small intestine and large intestine were determined after oral dosing to Wistar rats 1 and 4 h post-dose. Samples were analysed using LC-MS/MS and scintillation counting. RESULTS: Gut tissue accumulation of raltegravir was less than for lopinavir in silico, in vitro and ex vivo (P < 0.05). After oral administration to rats, raltegravir concentrations 4 h post-dose were lower in plasma (0.05 µM) compared with small intestine (0.47 µM, P = 0.06) and large intestine (1.36 µM, P < 0.05). However, raltegravir concentrations in the contents of both small intestine (4.0 µM) and large intestine (40.6 µM) were also high. CONCLUSIONS: In silico, in vitro and ex vivo data suggest low raltegravir accumulation in intestinal tissue. In contrast, in vivo animal data suggest raltegravir concentrates in intestinal tissue even when plasma concentrations are minimal. However, high raltegravir concentrations in gut contents are the likely driving factor behind this observation, rather than blood-to-tissue drug distribution. The methods described can be combined with clinical investigations to provide a complete strategy for selection of drugs with high gut accumulation.

Virological outcome at week 48 of three recommended first-line regimens using ultrasensitive viral load and plasma drug assay.

OBJECTIVES: To describe the virological and pharmacological outcomes of three different recommended once-daily first-line regimens in a cross-sectional analysis within an observational cohort using ultra-sensitive HIV quantification. PATIENTS AND METHODS: We enrolled all HIV-1-infected patients who initiated tenofovir/emtricitabine with efavirenz, darunavir/ritonavir or atazanavir/ritonavir as a first-line regimen between 1 November 2010 and 30 June 2012. An ultrasensitive viral load (VL) assay was performed and plasma drug concentrations at 24 h (C24) were determined at Week (W) 4, W12, W24, W36 and W48. RESULTS: Sixty patients initiated efavirenz, 81 darunavir/ritonavir and 27 atazanavir/ritonavir. A higher proportion of patients with a VL >100 000 copies/mL received darunavir/ritonavir (P = 0.022). At W48, 89%, 85% and 88% of the patients had a VL <50 copies/mL, 69%, 73% and 79% had a VL <20 copies/mL and 45%, 48% and 54% had a VL <1 copy/mL using the ultrasensitive assay in the efavirenz, darunavir/ritonavir and atazanavir/ritonavir groups, respectively. Patients with a detectable VL signal at W48 had a higher baseline VL than those with no detectable VL signal (P = 0.0001). A total of 92%, 93% and 91% of the efavirenz, darunavir and atazanavir C24 values were above the respective effective cut-offs. CONCLUSIONS: In this observational cohort, the choice of the regimen was related to the physicians' preferences and the patients' characteristics. The proportion of patients reaching VL <1 copy/mL at W48 was similar in the three regimens and was not associated with drug concentrations.

Serum drug concentrations predictive of pulmonary tuberculosis outcomes.

BACKGROUND: Based on a hollow-fiber system model of tuberculosis, we hypothesize that microbiologic failure and acquired drug resistance are primarily driven by low drug concentrations that result from pharmacokinetic variability. METHODS: Clinical and pharmacokinetic data were prospectively collected from 142 tuberculosis patients in Western Cape, South Africa. Compartmental pharmacokinetic parameters of isoniazid, rifampin, and pyrazinamide were identified for each patient. Patients were then followed for up to 2 years. Classification and regression tree analysis was used to identify and rank clinical predictors of poor long-term outcome such as microbiologic failure or death, or relapse. RESULTS: Drug concentrations and pharmacokinetics varied widely between patients. Poor long-term outcomes were encountered in 35 (25%) patients. The 3 top predictors of poor long-term outcome, by rank of importance, were a pyrazinamide 24-hour area under the concentration-time curve (AUC) ≤ 363 mg·h/L, rifampin AUC ≤ 13 mg·h/L, and isoniazid AUC ≤ 52 mg·h/L. Poor outcomes were encountered in 32/78 patients with the AUC of at least 1 drug below the identified threshold vs 3/64 without (odds ratio = 14.14; 95% confidence interval, 4.08-49.08). Low rifampin and isoniazid peak and AUC concentrations preceded all cases of acquired drug resistance. CONCLUSIONS: Low drug AUCs are predictive of clinical outcomes in tuberculosis patients.

Comparative In Vitro Killing by Pradofloxacin in Comparison to Ceftiofur, Enrofloxacin, Florfenicol, Marbofloxacin, Tildipirosin, Tilmicosin and Tulathromycin against Bovine Respiratory Bacterial Pathogens.

Pradofloxacin is the newest of the veterinary fluoroquinolones to be approved for use in animals-initially companion animals and most recently food animals. It has a broad spectrum of in vitro activity, working actively against Gram-positive/negative, atypical and some anaerobic microorganisms. It simultaneously targets DNA gyrase (topoisomerase type II) and topoisomerase type IV, suggesting a lower propensity to select for antimicrobial resistance. The purpose of this study was to determine the rate and extent of bacterial killing by pradofloxacin against bovine strains of Mannheimia haemolytica and Pasteurella multocida, in comparison with several other agents (ceftiofur, enrofloxacin, florfenicol, marbofloxacin, tildipirosin, tilmicosin and tulathromycin) using four clinically relevant drug concentrations: minimum inhibitory and mutant prevention drug concentration, maximum serum and maximum tissue drug concentrations. At the maximum serum and tissue drug concentrations, pradofloxacin killed 99.99% of M. haemolytica cells following 5 min of drug exposure (versus growth to 76% kill rate for the other agents) and 94.1-98.6% of P. multocida following 60-120 min of drug exposure (versus growth to 98.6% kill rate for the other agents). Statistically significant differences in kill rates were seen between the various drugs tested depending on drug concentration and time of sampling after drug exposure.

On the processes limiting oral drug absorption when amorphous solid dispersions are administered after a high-calorie, high-fat meal: Sporanox® pellets.

OBJECTIVES: 1) Identify processes limiting the arrival of itraconazole at the intestinal epithelium when Sporanox® amorphous solid dispersion (ASD) pellets are transferred from the stomach through the upper small intestine, after a high-calorie, high-fat meal. 2) Evaluate whether itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine are useful for the assessment of dose effects in the fed state and food effects on plasma levels. METHODS: Itraconazole concentrations, apparent viscosity, and solubilization capacity were measured in aspirates from the upper gastrointestinal lumen collected during a recently performed clinical study in healthy adults. Published itraconazole concentrations in plasma, after a high-calorie high-fat meal and Sporanox® ASD pellets, and in contents of the upper small intestine of healthy adults, after administration of Sporanox® ASD pellets in the fasted state, were used to achieve the second objective. RESULTS: When Sporanox® ASD pellets (up to 200 mg) are transferred from the stomach through the upper small intestine, after a high-calorie, high-fat meal, itraconazole concentrations in the colloidal phase or the micellar phase of aqueous contents of the upper small intestine are unsaturated, in most cases. During the first 3 h post-dosing after a high-calorie, high-fat meal, the impact of dose (200 mg vs. 100 mg) on itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine seems to underestimate the impact of dose on plasma levels. When Sporanox® ASD pellets are administered after a high-calorie, high-fat meal at the 200 mg dose level, itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine are, on average, lower than those achieved in fasted state. CONCLUSIONS: When Sporanox® ASD pellets are transferred from the stomach to the upper small intestine after a high-calorie, high-fat meal, itraconazole's arrival at the intestinal epithelium seems to be limited by its arrival at the colloidal phase of aqueous contents of the upper small intestine. The impact of dose (100 mg vs. 200 mg) on plasma levels after a high-calorie, high-fat meal and during the gastrointestinal transfer of Sporanox® pellets requires consideration of pre-systemic itraconazole metabolism. At the 200 mg dose level, after taking into consideration differences in the volume of the contents of the upper small intestine between the fasted and the fed state during the gastrointestinal transfer of Sporanox® ASD pellets, itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine suggest a mild negative food effect on average plasma levels; published clinical data are inconclusive.

Recommended dosages of analgesic and sedative drugs in intensive care result in a low incidence of potentially toxic blood concentrations.

Background: Standard dosages of analgesic and sedative drugs are given to intensive care patients. The resulting range of blood concentrations and corresponding clinical responses need to be better examined. The purpose of this study was to describe daily dosages, measured blood concentrations, and clinical responses in critically ill patients. The purpose was also to contribute to establishing whole blood concentration reference values of the drugs investigated. Methods: A descriptive study of prospectively collected data from 302 admissions to a general intensive care unit (ICU) at a university hospital. Ten drugs (clonidine, fentanyl, morphine, dexmedetomidine, ketamine, ketobemidone, midazolam, paracetamol, propofol, and thiopental) were investigated, and daily dosages recorded. Blood samples were collected twice daily, and drug concentrations were measured. Clinical responses were registered using Richmond agitation-sedation scale (RASS) and Numeric rating scale (NRS). Results: Drug dosages were within recommended dose ranges. Blood concentrations for all 10 drugs showed a wide variation within the cohort, but only 3% were above therapeutic interval where clonidine (57 of 122) and midazolam (38 of 122) dominated. RASS and NRS were not correlated to drug concentrations. Conclusion: Using recommended dose intervals for analgesic and sedative drugs in the ICU setting combined with regular monitoring of clinical responses such as RASS and NRS leads to 97% of concentrations being below the upper limit in the therapeutic interval. This study contributes to whole blood drug concentration reference values regarding these 10 drugs.

Development of a simultaneous LC-MS/MS analytical method for plasma: 16 antipsychotics approved in Japan and 4 drug metabolites.

The increased risk of adverse drug reactions due to the concomitant use of antipsychotics is problematic in the treatment of schizophrenia. Therefore, the simultaneous analysis of their plasma concentrations is required. In this study, we developed a simultaneous liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for analyzing plasma antipsychotics approved in Japan for therapeutic drug monitoring (TDM) applications. First, we counted the prescriptions for 16 antipsychotics and concomitant drugs used at the Tohoku University Hospital. LC-MS/MS was used for the simultaneous analysis of 16 antipsychotics and four drug metabolites. This analysis was conducted using a combination of selected reaction monitoring mode and reversed-phase chromatography. Following the examination of the MS/MS and LC conditions, an analytical method validation test was conducted. The developed method was used to analyze plasma antipsychotic levels in patients with schizophrenia. One-third of the patients received treatment with multiple antipsychotics. Under LC-MS/MS conditions, LC separation was performed using a combination of a C18 column and ammonium formate-based mobile phases with a gradient flow. The calibration curves were optimized by adjusting the ion abundance, and 11 compounds met the criteria for intra- and inter-day reproducibility tests. Some stability test results did not meet these criteria; therefore, further investigation is required. The developed method permitted the measurement of all the plasma parameters, including concentrations above the therapeutic range. Therefore, this method may be useful in the daily TDM practice of antipsychotics.