Development of a High-Linearity Voltage and Current Probe with a Floating Toroidal Coil: Principle, Demonstration, Design Optimization, and Evaluation.

As the conventional voltage and current (VI) probes widely used in plasma diagnostics have separate voltage and current sensors, crosstalk between the sensors leads to degradation of measurement linearity, which is related to practical accuracy. Here, we propose a VI probe with a floating toroidal coil that plays both roles of a voltage and current sensor and is thus free from crosstalk. The operation principle and optimization conditions of the VI probe are demonstrated and established via three-dimensional electromagnetic wave simulation. Based on the optimization results, the proposed VI probe is fabricated and calibrated for the root-mean-square (RMS) voltage and current with a high-voltage probe and a vector network analyzer. Then, it is evaluated through a comparison with a commercial VI probe, with the results demonstrating that the fabricated VI probe achieved a slightly higher linearity than the commercial probe: R2 of 0.9967 and 0.9938 for RMS voltage and current, respectively. The proposed VI probe is believed to be applicable to plasma diagnostics as well as process monitoring with higher accuracy.

Development of the Measurement of Lateral Electron Density (MOLE) Probe Applicable to Low-Pressure Plasma Diagnostics.

As the importance of measuring electron density has become more significant in the material fabrication industry, various related plasma monitoring tools have been introduced. In this paper, the development of a microwave probe, called the measurement of lateral electron density (MOLE) probe, is reported. The basic properties of the MOLE probe are analyzed via three-dimensional electromagnetic wave simulation, with simulation results showing that the probe estimates electron density by measuring the surface wave resonance frequency from the reflection microwave frequency spectrum (S11). Furthermore, an experimental demonstration on a chamber wall measuring lateral electron density is conducted by comparing the developed probe with the cutoff probe, a precise electron density measurement tool. Based on both simulation and experiment results, the MOLE probe is shown to be a useful instrument to monitor lateral electron density.

Rapid determination of remdesivir (SARS-CoV-2 drug) in human plasma for therapeutic drug monitoring in COVID-19-Patients.

To tackle the harmful consequences of the widespread COVID-19 pandemic, a broad-spectrum anti-viral drug remdesivir (RDV) has gained the utmost attention recently due to its promising application in treating COVID-19 patients. However, a fast and sensitive analytical methodology is important to monitor RDV drug profile in human plasma for pharmacokinetics (PK) and therapeutic drug monitoring (TDM). In this study, we demonstrate an improved vortex-assisted salt-induced liquid-liquid microextraction (VA-SI-LLME) technique coupled with UHPLC-PDA and UHPLC-MS/MS for rapid determination of RDV in human plasma. This technique involves simple one-step protein precipitation with hydrochloric acid and subsequent extraction with acetonitrile for analysis. Under the optimal VA-SI-LLME conditions (500 µL of acetonitrile with 2.5 g ammonium sulfate under 2 min vortex extraction), method validation results indicated an excellent correlation coefficient of 0.9969 for UHPLC-PDA (monitored at 254 nm) and 0.9990 for UHPLC-MS/MS (monitored at electrospray ionization with + ion mode transitions of m/z 603.1→m/z 402.20 and m/z 603.1→ m/z 199.90). The detection and quantification limits were 1.5 and 5 ng/mL for UHPLC/PDA, and 0.3 and 1 ng/mL for UHPLC-MS/MS, respectively. The developed method showed excellent extraction recoveries between 90.79-116.74 % and 85.68-101.34 % with intraday and interday precision ≤ 9.59 for both methods. These results proved that the developed method is a simple, fast, and sensitive analytical method that can be applied as a standard analytical tool for PK and TDM studies of RDV in clinical trials during the current worldwide outbreak.

Erlotinib pharmacokinetics: a critical parameter influencing acute toxicity in elderly patients over 75 years-old.

Background Older non-small cell lung cancer (NSCLC) patients under erlotinib are reported to experience more acute toxicity. We hypothesized that modifications in erlotinib pharmacokinetics might explain this observation. Methods A monocentric prospective clinico-pharmacological study included stage IIIb/IV NSCLC consecutive pts. treated with erlotinib. The plasma concentration of erlotinib (Ce) was measured at steady state on day 15. We studied the relationship between age > 75 years, and Ce, using the Mann-Whitney U test and with the occurrence of acute toxicity, using a Fisher's test. Results A total of 53 pts. were analyzed. Median age was 68 years (31-83), 56 % were female. All pts. > 75 years experienced toxicity: all grade acute adverse events were 1.6 fold more frequent (100 % vs 61 %; OR 95 % CI [1.9-INF]; p = 0.003). At day 15, Ce increased with age. Over 75 years old, the mean Ce was 1.5 fold higher: 2091 ng/mL (95 % CI [1476; 2706]) vs 1359 (95 % CI [1029; 1689]; p = 0.024). In pts. over 80 years old, the mean Ce was doubled: 2729 (95 % CI [1961; 3497]) vs 1358 ng/mL (95 % CI [1070; 1646]; p = 0.0019). Reduced lean body mass over 75 years (median 36.6 kg versus 49.1 kg) might account for these differences. Finally, the risk of early erlotinib discontinuation was increased by 11 in older pts. (33 % vs 3 % OR 17.2; 95 % CI [1.7; 892.5] p = .005). Conclusion The risk of overexposure to erlotinib increases with age. Reduced lean body mass may explain erlotinib pharmacokinetics and excessive acute toxicity in the elderly.

Monitoramento plasmático e análise PK/PD dos antimicrobianos vancomicina e piperacilina no controle das infecções em pacientes queimados / Serum monitoring and PK/PD analysis of vancomycin and piperacillin for sepsis control in burn patients

Introdução: Reportam-se modificações metabólicas e hemodinâmicas em pacientes críticos em sepse e incluem-se neste grupo, os grandes queimados. Nesses pacientes ocorrem profundas alterações na farmacocinética de agentes antimicrobianos hidrofílicos prescritos no tratamento empírico das infecções bacterianas graves. Então, o alvo terapêutico não é alcançado em decorrência das concentrações plasmáticas desses antimicrobianos serem inferiores às requeridas para o controle das infecções. Na suspeita de sepse, a terapia antimicrobiana de primeira escolha prevê administração sistêmica dos antimicrobianos a vancomicina e a piperacilina, sendo esta última associada à tazobactana, um inibidor da beta-lactamase. Objetivo: Propôs-se nesse projeto a investigação da farmacocinética da vancomicina e da piperacilina através do monitoramento plasmático. Propôs-se ainda a avaliação da efetividade dos dois antimicrobianos na dose empírica recomendada com base na função renal aos pacientes críticos grandes queimados em sepse por patógeno hospitalar. Métodos: Investigaram-se 42 pacientes grandes queimados em terapia intensiva com lesões de 2° grau profundo e de 3° grau com suspeita de sepse por patógeno hospitalar. A prescrição constou de terapia combinada de vancomicina e piperacilina nas doses empíricas recomendadas com base na função renal de cada paciente. Seguem as características dos pacientes investigados: adultos de ambos os sexos (33M/9F), médias/ DP: 40,9±17,5 anos, 70,1±11,5 Kg, 33,6±20,7% de superfície corpórea total queimada (SCTQ), sendo 37/42 pacientes apresentaram função renal normal, e 5/42 pacientes com insuficiência renal, sem necessidade de prescrição de diálise pelo nefrologista. Registrou-se trauma térmico/ elétrico em 39/3; a lesão inalatória ocorreu em 25 pacientes. Efetuou-se coleta seriada de 2-3 amostras sanguíneas (Vacutainer/EDTA sódico); após separação do sangue por centrifugação a 2800g para obtenção do plasma, realizou-se o processamento laboratorial para os dois analitos pelo monitoramento plasmático da vancomicina e da piperacilina através da cromatografia líquida de alta eficiência. Realizou-se o estudo farmacocinético com base no modelo aberto monocompartimental. Através da análise PK/PD foi possível determinar os índices de efetividade para a vancomicina a partir da razão da área sob a curva no intervalo de 24 horas e a concentração inibitória mínima ASCss 0-24/CIM > 400, e para a piperacilina 70%fΔT>CIM; o significado desse último índice determinado para o derivado ß-lactâmico está relacionado a fração do intervalo de dose em que a concentração plasmática livre da piperacilina permanece acima da CIM. Resultados: Registrou-se alteração da farmacocinética da vancomicina e da piperacilina nos pacientes queimados com função renal normal pela comparação entre cada paciente e o valor de referência reportado para voluntários sadios. Nos pacientes com insuficiência renal registrou-se o prolongamento da meia vida biológica pela alteração na depuração e/ou no volume de distribuição. Registrou-se farmacocinética alterada em diferentes proporções tanto nos pacientes queimados com função renal preservada, como naqueles com disfunção renal. Após a análise PK/PD, a dose empírica de vancomicina administrada aos pacientes com função renal normal, registrou-se cobertura em 37/37 pacientes contra patógenos sensíveis (CIM 1mg/L), caindo para 18/37 (49%) pacientes para patógenos, CIM 2 mg/L. Não se registrou cobertura contra patógenos CIM>2 mg/L (CIM 4mg/L) independente da função renal dos pacientes. Após a dose empírica prescrita na função renal preservada, a cobertura da piperacilina ocorreu até CIM 4mg/L, para os patógenos sensíveis, caindo para 34/37 (92%) CIM 8 mg/L. Apenas 22/37 (60%) pacientes se encontraram protegidos contra patógenos sensíveis mais agressivos CIM 16 mg/L Pseudomonas aeruginosa e Enterococcus spp. Conclusão: O monitoramento plasmático da vancomicina e da piperacilina indica que a dose empírica recomendada para os dois agentes não alcança efetividade no controle das infecções causadas por patógenos hospitalares sensíveis à vancomicina (CIM>1mg/L) e à piperacilina (CIM >4 mg/L) em consequência de níveis plasmáticos inferiores aos requeridos no controle das infecções, devido a profundas alterações na farmacocinética desses antimicrobianos

Introduction: Metabolic and hemodynamic changes were reported in critically ill patients including burn patients in sepsis. Then, pharmacokinetics is altered in those patients mainly for hydrophilic antimicrobial agents prescribed for the control of severe bacterial infections; consequently, the therapeutic target wasn't reached based on drug plasma concentrations lower than expected. Antimicrobial therapy recommended in sepsis suspicious is based in a combination of two antimicrobials; vancomycin, a glycopeptides derivative and a beta-lactam agent piperacillin-tazobactam, a beta-lactamase inhibitor. Objective: It was proposed a pharmacokinetic investigation for vancomycin and piperacillin based on drug plasma monitoring followed by drug effectiveness measurements by PK/PD analysis after the empiric dose regimen recommended to normal renal function or renal failure burn patients in sepsis. Methods: 42 adult burn patients of both gender (33M/9F) with deep 2nd and 3rd injuries in septic shock by nosocomial pathogens under intensive care were investigated. A combined antimicrobial therapy at the recommended empirical dose regimen vancomycin-piperacillin was prescribed on the basis of renal function. Characteristics of population of patients investigated, means/SD were: 40.9±17.5 yrs, 70.1±11.5 kg, 33.6±20.7% total burn surface area (TBSA). Normal renal function was registered in 37/42 patients against 5/42 of them with renal failure. Thermal/electrical injuries occur in 39/3, and inhalation injury were in 25 of them. A serial of 2-3 blood samples were obtained from venous catheter into vacuum tubes (sodium EDTA); after centrifugation (2800g) plasma samples were obtained for drug plasma monitoring; both analytes, vancomycin and piperacillin were quantified by high performance liquid chromatography. Pharmacokinetics investigation based on one compartment open model was performed. PK/PD analysis was done to determine antimicrobial effectiveness against nosocomial pathogens isolated. Recommended drug effectiveness index was AUCss 0-24/MIC > 400 for vancomycin and 70%fΔT>MIC for piperacillin. Results: Pharmacokinetics for both antimicrobials investigated showed to be altered in a different extension for vancomycin and piperacillin in burn patients with normal renal function by comparison with reference data reported in healthy adult volunteers. PK/PD analysis indicated that after the initial dose regimen 2g daily for patients with normal renal function, the vancomycin effectiveness occurs only for susceptible pathogens MIC 1mg/L, once drug effectiveness falls to 49% (18/37) against pathogens (MIC 2mg/L). Similarly, piperacillin effectiveness occurs just for susceptible pathogens MIC ≤ 4 mg/L in patients with normal renal function, once only 22/37 (60%) of patients reached the target MIC 16mg/L for Pseudomonas aeruginosa and Enterococcus spp. Conclusion: Vancomycin and piperacillin plasma monitoring indicated that the therapeutic target wasn´t reached with the empiric dose regimen recommended against nosocomial pathogens vancomycin susceptible (MIC>1mg/L) and piperacillin susceptible (MIC >4 mg/L) due to plasma levels lower than expected as a consequence of kinetic disposition altered for both antimicrobials

Pharmacokinetic-pharmacodynamic correlation of imipenem in pediatric burn patients using a bioanalytical liquid chromatographic method / Correlação farmacocinética-farmacodinâmica de imipenem em pacientes queimados pediátricos utilizando um método bioanalítico de cromatografia líquida

A bioanalytical method was developed and applied to quantify the free imipenem concentrations for pharmacokinetics and PK/PD correlation studies of the dose adjustments required to maintain antimicrobial effectiveness in pediatric burn patients. A reverse-phase Supelcosil LC18 column (250 x 4.6 mm 5 micra), binary mobile phase consisting of 0.01 M, pH 7.0 phosphate buffer and acetonitrile (99:1, v/v), flow rate of 0.8 mL/min, was applied. The method showed good absolute recovery (above 90%), good linearity (0.25-100.0 µg/mL, r²=0.999), good sensitivity (LLOQ: 0.25 µg/mL; LLOD: 0.12 µg/mL) and acceptable stability. Inter/intraday precision values were 7.3/5.9%, and mean accuracy was 92.9%. A bioanalytical method was applied to quantify free drug concentrations in children with burns. Six pediatric burn patients (median 7.0 years old, 27.5 kg), normal renal function, and 33% total burn surface area were prospectively investigated; inhalation injuries were present in 4/6 (67%) of the patients. Plasma monitoring and PK assessments were performed using a serial blood sample collection for each set, totaling 10 sets. The PK/PD target attained (40%T>MIC) for each minimum inhibitory concentration (MIC: 0.5, 1.0, 2.0, 4.0 mg/L) occurred at a percentage higher than 80% of the sets investigated and 100% after dose adjustment. In conclusion, the purification of plasma samples using an ultrafiltration technique followed by quantification of imipenem plasma measurements using the LC method is quite simple, useful, and requires small volumes for blood sampling. In addition, a small amount of plasma (0.25 mL) is needed to guarantee drug effectiveness in pediatric burn patients. There is also a low risk of neurotoxicity, which is important because pharmacokinetics are unpredictable in these critical patients with severe hospital infection. Finally, the PK/PD target was attained for imipenem in the control of sepsis in pediatric patients...

Desenvolveu-se e aplicou-se método bioanalítico para quantificar concentrações de imipenem livre para estudos de farmacocinética (PK) e de correlação PK/PD dos ajustes de dose requeridos para manter a efetividade antimicrobiana em pacientes pediátricos queimados. Utilizou-se coluna Supelcosil LC18 (250 x 4,6 mm 5 micra), fase móvel binária, consistindo de tampão fosfato 0,01M pH 7,0 e acetonitrila (99:1, v/v) e fluxo de 0,8 mL/min. O método mostrou boa recuperação absoluta (acima de 90%), boa linearidade (0,25-100,0 µg/mL, r²=0.999), boa sensibilidade (LLOQ: 0,25 µg/mL; LLOD: 0,12 µg/mL) e estabilidade aceitável. Os valores de precisão inter/intradia foram 7,3/5,9% e a exatidão média foi de 92,9%. O método bioanalítico foi aplicado para quantificar concentrações de fármaco livre em crianças com queimaduras, Seis pacientes pediátricos queimados (idade média de 7,0 anos, 27,5 kg), com função renal normal e 33% da superfície total queimada foram investigados prospectivamente. Lesões por inalação estavam presentes em 4/6 (67%) dos pacientes. O monitoramento plasmático e a as avaliações de PK foram efetuadas utilizando coleção de amostras seriais de sangue para cada série, totalizando 10 conjuntos. O alvo PK/PD alcançado (40%T>MIC) para cada concentração inibitória mínima (MIC: 0,5, 1,0, 2,0, 4,0 mg/L) ocorreu em porcentagem maior do que 80% dos conjuntos investigados e 100% após o ajuste de dose. Em conclusão, a purificação das amostras do plasma usando técnica de ultrafiltração seguida de quantificação das medidas do imipenem no plasma usando método de cromatografia líquida é bastante simples, útil e necessita de pequenos volumes para as amostras de sangue. Além disso, pequena quantidade de plasma (0,25 mL) é necessário para garantir a efetividade do fármaco nos pacientes pediátricos queimados. Há, ainda, baixo risco de neurotoxicidade, o que é importante, visto que as farmacocinéticas são imprevisíveis nesses pacientes...

Imatinib plasma monitoring-guided dose modification for managing imatinib-related toxicities in gastrointestinal stromal tumor patients.

Imatinib, the first-line treatment in patients with advanced gastrointestinal stromal tumors (GIST), is generally well tolerated, although some patients have difficulty tolerating the standard dose of 400 mg/day. Adjusting imatinib dosage by plasma level monitoring may facilitate management of patients who experience intolerable toxicities due to overexposure to the drug. We present two cases of advanced GIST patients in whom we managed imatinib-related toxicities through dose modifications guided by imatinib plasma level monitoring. Imatinib blood level testing may be a promising approach for fine-tuning imatinib dosage for better tolerability and optimal clinical outcomes in patients with advanced GIST.

Imatinib Plasma Monitoring-Guided Dose Modification for Managing Imatinib-Related Toxicities in Gastrointestinal Stromal Tumor Patients

Imatinib, the first-line treatment in patients with advanced gastrointestinal stromal tumors (GIST), is generally well tolerated, although some patients have difficulty tolerating the standard dose of 400 mg/day. Adjusting imatinib dosage by plasma level monitoring may facilitate management of patients who experience intolerable toxicities due to overexposure to the drug. We present two cases of advanced GIST patients in whom we managed imatinib-related toxicities through dose modifications guided by imatinib plasma level monitoring. Imatinib blood level testing may be a promising approach for fine-tuning imatinib dosage for better tolerability and optimal clinical outcomes in patients with advanced GIST.

Abordagem farmacocinética e farmacodinâmica no monitoramento terapêutico de antimicrobianos em pacientes queimados da unidade de terapia intensiva / Pharmacokinetic and pharmacodynamic approach for antimicrobial therapeutic monitoring in burn patients from the intensive care unit

Introdução: A sepse é a maior causa de morbidade e mortalidade em pacientes queimados, uma vez que profundas alterações ocorrem na farmacocinética de agentes antimicrobianos prescritos para o controle das infecções. Além disso, pacientes queimados podem apresentar quadro de infecção por germes da comunidade, numa fase precoce de internação na UTI, e devem receber antimicrobianos que diferem daqueles indicados na sepse. Na vigência de infecção fúngica, o quadro se torna ainda mais grave para os pacientes queimados de prolongada internação e imunocomprometidos. Objetivo: Realizar o monitoramento plasmático de oito antimicrobianos largamente prescritos na UTI, a investigação da farmacocinética e a modelagem PK-PD para o ajuste do regime de dose e controle das infecções em pacientes queimados. Casuística: Investigaram-se 32 pacientes queimados internados na UTI/Unidade de Queimados - Divisão de Cirurgia Plástica do HC FMUSP, portadores de infecção recebendo pela via sistêmica sete antimicrobianos e um antifúngico. Métodos- Etapa Clinica: Os pacientes receberam os antimicrobianos geralmente em associação para o controle das infecções seguindo as recomendações da CCIH do hospital relativas ao regime de dose empírica inicial do controle de infecção na UTI de Queimados, na fase precoce e tardia da internação. Realizou-se o monitoramento plasmático do fluconazol, para a infecção fúngica, e dos sete antimicrobianos mais prescritos na UTI para os germes da comunidade e hospitalares (cefepime, ciprofloxacino, imipenem, oxacilina, piperacilina, sulfametoxazol e vancomicina) através das coletas de amostras sanguíneas de pico (termino da infusão) e vale (imediatamente antes da dose subseqüente). Complementarmente, a critério Clínico, foram colhidas amostras seriadas de sangue (pico, 1ª, 2ª, 4ª, 6ª e vale), totalizando seis coletas, para investigação da farmacocinética do agente que requereu ajuste de dose e individualização de terapia no paciente queimado...

Introduction: Sepsis is a main cause of morbidity and mortality in burn patients, once pharmacokinetics of antimicrobials prescribed for the control of infections are significantly altered in those patients. In addition, burn patients in the ICU, initially can present infections by community microbial and must receive different antimicrobials than those prescribed for sepsis. On the other hand, burn immunocompromized patients with prolonged staying in the ICU, re-incidence of sepsis and fungal infection requires an effective antifungal agent that must be associated to the antimicrobials prescription. Objective: Therapeutic plasma monitoring of eight antimicrobials largely prescribed to burn patients from the ICU, Pharmacokinetic and PK-PD modeling for dose adjustment and for the control of infections. Study design: Thirty two burn inpatients with infections from the ICU Burns- Division of Plastic Surgery of Clinics Hospital Medical School University of Sao Paulo received systemically antimicrobials/ antifungal agents. Methods - Clinical Procedures: In general burn patients received several antimicrobial agents as recommended by the Control of Hospital Infection Committee as empirical dose at the beginning of therapy and also afterwards in the ICU. The control of infections by community microbials or yet by hospital microbials, and also for fungal infection, was performed by drug plasma monitoring of cefepime, ciprofloxacin, imipenem, oxacillin, piperacillin, sulphamethoxazole, vancomycin and fluconazole after blood sample collection at the peak and at the trough. Complementary, usually by clinical criteria, six blood sample collections were performed at time dose interval (end of drug infusion, 1st, 2nd, 4th, 6th and at the trough) for pharmacokinetic purposes, dose adjustment and individualization of drug therapy for burn patients. Blood sample collection was done by the physician from the ICU by venous catheter (2mL/each into blood collection tubes sodium...

Monitoramento terapêutico e modelagem farmacocinética de antimicrobianos em pacientes queimados da unidade de terapia intensiva / Therapeutic drug monitoring and pharmacokinetics of antimicrobial agents in burn patients from the Intensive care unit

A sepse após a injúria térmica é a maior causa de morbidade e mortalidade em pacientes queimados, uma vez que profundas alterações ocorrem na farmacocinética de agentes antimicrobianos. Investigaram-se trinta e um pacientes, portadores de sepse documentada e apresentando lesões ativas; utilizou-se o tratamento empírico conforme seguem os regimes de dose: 1 g, 12/12 h para a vancomicina, 1 g, 6/6 h para o imipenem e 2 g, 8/8 h para o cefepime. Sete coletas seriadas de sangue foram realizadas através de cateter venoso (2 mL/cada); o plasma foi obtido pela centrifugação e armazenado no congelador (-80o C) até o ensaio. A concentração plasmática dos antimicrobianos foi determinada simultaneamente pela aplicação do método bioanalítico desenvolvido no estudo. O método de cromatografia líquida de alta eficiência demonstrou boa linearidade, precisão e exatidão para a determinação simultânea da vancomicina, cefepime e imipenem plasmáticos; a plicação desse método bioanalítico permitiu o monitoramento plasmático terapêutico e o estudo farmacocinético. Com base nos resultados obtidos de concentração plasmática versus tempo, aplicou-se a modelagem para investigar a farmacocinética desses agentes antimicrobianos nos pacientes queimados. Os parâmetros cinéticos foram estimados com base no modelo aberto de um compartimento pela aplicação do programa PK Solutions v. 2.0; a estatística foi realizada pela utilização do programa GraphPad Prism v. 4.0. Com base na farmacocinética alterada, as concentrações obtidas para a vancomicina e imipenem se mostraram abaixo dos valores recomendados para atingir eficácia; por outro lado, as concentrações obtidas para o cefepime se mostraram dentro da faixa recomendada para atingir eficácia, uma vez que não se registrou alteração da farmacocinética deste antimicrobiano nos pacientes queimados. Desta forma, o monitoramento plasmático terapeutico se mostrou importante, permitindo o ajuste de dose para a vancomicina e para o imipenem, uma vez que...

Sepsis after thermal injury is the major cause of morbidity and mortality in burn patients, once deep changes on the pharmacokinetics of antimicrobials agents are expected. Thirty one burn patients were investigated, all of them had documented sepsis and presented active lesions; they were treated with empirical dose regimen as follows: 1 g, 12/12 h for vancomycin, 1 g, 6/6 h for imipenem and 2 g, 8/8 h for cefepime. A serial of seven blood samples were collected from the venous catheter (2 mL/each); plasma was obtained by centrifugation and storaged in an ultra-low freezer (-80o C) until assay. Drug plasma concentration was determined simultaneously by application of a bioanalytical method described previously. High performance liquid chromatographic method showed good linearity, precision and accuracy for vancomycin, cefepime and imipenem plasma measurements; its application permitted therapeutic drug monitoring and pharmacokinetic studies. Pharmacokinetic modeling was applied to data obtained based on drug plasma concentrations versus time, to investigate those antimicrobial agents in burn patients. Estimated kinetic parameters were based on the one compartment open model by application the software PK Solutions v. 2.0; statistics was performed by using the software GraphPad Prism v. 4.0. Based on altered pharmacokinetics, obtained plasma concentrations to reach drug efficacy were below the recommended values for vancomycin and imipenem; on the other hand, cefepime plasma concentrations to reach drug efficacy were in the recommended range, once its pharmacokinetics didnt change in burn patients. Then, therapeutic plasma monitoring was cost-effective permitting dose adjustment for vancomycin and imipenem, once the minimum effective concentration (MEC) wasnt reached for both antimicrobial agents by using the empirical dose regimen for burn patients. On the other hand, cefepime plasma monitoring was also cost-effective, since burn patients long term therapy can...

Determining plasma morphine levels using GC-MS after solid phase extraction to monitor drug levels in the postoperative period

OBJECTIVE: To implement a selective and sensitive analytical method to quantify morphine in small volumes of plasma by gas-liquid chromatography-mass spectrometry (GC-MS), aimed at post-operatively monitoring the drug. METHOD: A gas-liquid chromatographic method with mass detection has been developed to determine morphine concentration in plasma after solid phase extraction. Morphine-d3 was used as an internal standard. Only 0.5 mL of plasma is required for the drug solid-phase extraction in the Bond Elut-Certify®, followed by the quantification of morphine derivative by GC-MS using a linear temperature program, a capillary fused silica column, and helium as the carrier and make-up gas. The method was applied to determine morphine content in plasma samples of four patients during the postoperative period of cardiac surgery. Patient-controlled analgesia with morphine was performed by a venous catheter, and a series of venous blood samples were collected. After the oro-After the orotracheal extubation, morphine plasma levels were monitored for up to 36 hours. RESULTS: The run time was 16 minutes because morphine and the internal standard were eluted after 8.8 minutes. The GC-MS method had 0.5 -1000 ng/mL linearity range (r²=0.9995), 0.1 ng/mL limit of detection, intraday and interday precision equivalent to 1.9 percent and 6.8 percent, and 0.1 percent and 0.8 percent systematic error (intraday and interday, respectively). The analytical method showed optimal absolute (98 percent) and relative (100.7 percent) recoveries. Morphine dose requirements and plasma levels are discussed. CONCLUSION: The analytical gas-liquid chromatography-mass spectrometry method is selective and adequate for morphine measurements in plasma for applications in clinical studies.