Validação de metodologia analítica e estudo de estabilidade para quantificação sérica de paracetamol / Analytical methodology validation and stability study for serum quantification of acetaminophen

INTRODUÇÃO E OBJETIVO: Paracetamol ou acetaminofeno é atualmente um dos analgésicos-antipiréticos mais utilizados, principalmente em crianças. Porém o fácil acesso ao medicamento e o desconhecimento da população sobre seus efeitos nocivos têm aumentado muito o número de intoxicações por esse medicamento. A análise da concentração sérica de paracetamol confirma o diagnóstico. O resultado não só tem valor de certeza diagnóstica como também avalia o risco de hepatotoxicidade, indicando uso ou não do antídoto específico n-acetilcisteína. O objetivo deste trabalho foi propor um método analítico para quantificação sérica do paracetamol por espectrofotometria visível em 430 nm. MATERIAIS E MÉTODOS: Após desproteinização da amostra, acetaminofeno (n-acetil-p-aminofenol) reage com nitrito de sódio, formando 2,4-nitro-4-acetaminofenol, que assume coloração amarela em meio alcalino. As figuras de mérito linearidade, precisão, exatidão, robustez, recuperação, limites de detecção e qualificação foram avaliadas segundo critérios preconizados pelo International Conference on Harmonisation (ICH) e pela Agência Nacional de Vigilância Sanitária (ANVISA). O estudo de estabilidade foi realizado após ciclos de congelamento/descongelamento, curta duração, longa duração sob refrigeração e em freezer. RESULTADOS: O método se mostrou linear de 20 a 300 mg/l. Os limites de detecção e quantificação foram de respectivamente 3,6 mg/l e 20 mg/l. CONCLUSÃO: O método se mostrou preciso, exato e robusto e apresentou boa recuperação. As amostras-controle foram estáveis nas condições testadas. O método desenvolvido demonstrou possuir todos os parâmetros necessários para ser aplicado na quantificação de paracetamol em amostras de plasma ou soro humano para análise de emergência. Além disso, é uma técnica simples, de rápida execução e baixo custo.

INTRODUCTION AND OBJECTIVE: Acetaminophen or paracetamol is currently one of the most used analgesic-antipyretic agents, mainly with children. However, both the easy access to this medicine and the population's unawareness of its toxic effects have contributed to a rise in the number of intoxications caused by this drug. Assessment of serum acetaminophen confirms the diagnosis. Not only does the result have diagnostic reliability but it also evaluates the risk of hepatotoxicity, indicating or not the administration of the specific antidote n-acetylcysteine. The aim of this study is to present an analytical method to the assessment of serum acetaminophen by spectrophotometric detection at 430 nm. MATERIALS AND METHODS: After sample deproteinization, acetaminophen (n-acetyl-p-aminophenol) reacts with sodium nitrite forming 2.4-nitro-4-acetaminophenol, which becomes yellowish in alkaline medium. For method validation, linearity, precision, accuracy, robustness, recovery and detection limits were evaluated according to ICH and ANVISA criteria. The stability study was carried out after freezing/defreezing cycles, short-time duration, long-time duration under refrigeration and long-time duration under freezing. RESULTS: The method showed to be linear from 20 to 300 mg/l. The detection and quantification limits were 3.6 mg/l and 20 mg/l, respectively. CONCLUSION: The method was precise, accurate and robust and showed good recovery. The control-samples were stable in all tested conditions. The method developed presented all the necessary parameters to be applied in acetaminophen quantification in plasma samples or human serum for emergency analyzes. Furthermore, it is a simple, time and cost-effective technique.

Management of acute paracetamol poisoning in a tertiary care hospital.

OBJECTIVES: To compare the management of acute paracetamol poisoning with the best evidence available, and to determine the effect of plasma paracetamol level estimation on the management. DESIGN: Descriptive study with an intervention. SETTING: Medical wards of the National Hospital of Sri Lanka, Colombo. PATIENTS: Patients admitted with a history of acute paracetamol poisoning. INTERVENTION: Measurement of plasma paracetamol. METHODS: Data were obtained from the patients, medical staff and medical records. Plasma paracetamol was estimated between 4-24 hours of paracetamol ingestion. The current management practices were compared with the best evidence on acute paracetamol poisoning management. RESULTS: 157 patients were included. The mean ingested dose of paracetamol was 333 mg/kg body weight. Majority of the patients (84%) were transfers. Induced emesis and activated charcoal were given to 91% of patients. N-acetylcysteine was given to 66, methionine to 55, and both to 2. Aclinically important delay in the administration of antidotes was noted; 68% of patients received antidotes after 8 hours of the acute ingestion. Only 31 (26%) had paracetamol levels above the Rumack-Matthew normogram. 74 patients received an antidote despite having a plasma paracetamol level below the toxic level according to the normogram. INTERPRETATION: Management of acute paracetamol poisoning could be improved by following best available evidence and adapting cheaper methods for plasma paracetamol estimation.

Absorption and metabolism of paracetamol in rats drinking high concentration of arsenic.

The effect of chronic intake of arsenic on the plasma concentration of paracetamol in rat was investigated. Rats received saline water with or without arsenic trioxide (10 mg/kg body weight/day) by gastric gavage on every alternate day for 29 days. A single dose of paracetamol (range 10 infinity 40 mg/kg body weight) was administered by gastric gavage to both arsenic-untreated and -treated rats on 30(th) day. Rats were sacrificed after 30 min and the amounts of free paracetamol and its metabolites in plasma were estimated using isocratic reverse-phase High Performance Liquid Chromatography (HPLC). Arsenic toxicity reduced the plasma concentration of paracetamol to 53 - 65% when compared with the rats received no added arsenic. There were maximum 67.4 and 76.9% inhibitions of sulfate and cysteine conjugations of paracetamol respectively. But arsenic had no effect on glucuronide and mercapturate conjugations. Both liver and small intestine showed increased accumulation of arsenic and decreased amount of glutathione in arsenic-treated rats. This study suggests that chronic ingestion of arsenic inhibit the absorption and metabolism of paracetamol.

¿Contribuye el TNF-alfa a la fisiopatolog'ia de las hepatopatias? / Does TNF-alpha contribute to liver disease physiopathology?

The aim of the present paper is to establish the possible role of serum TNF in the pathophysiology of three experimental models of liver injury: paracetamol intoxication, cholestasis followed by paracetamol intoxication and cholestasis. We concluded that under our experimental conditions the serum TNF-alpha levels were not responsible for the inflammatory phenomena described in our previous paper as apopt.

Gastric emptying in rats with acetaminophen-induced hepatitis

The objective of this work was to study the gastric emptying (GE) of liquids in fasted and sucrose-fed rats with toxic hepatitis induced by acetaminophen. The GE of three test meals (saline, glucose and mayonnaise) was evaluated in Wistar rats. For each meal, the animals were divided into two groups (N = 24 each). Group I was fed a sucrose diet throughout the experiment (66 h) while group II was fasted. Forty-two hours after the start of the experiment, each group was divided into two subgroups (N = 12 each). Subgroup A received a placebo and subgroup B was given acetaminophen (1 g/kg). Twenty-four hours later, the GE of the three test meals was assessed and blood samples were collected to measure the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and acetaminophen. In group IB, the mean AST and ALT values were 515 and 263 IU/l, respectively, while for group IIB they were 4014 and 2472 IU/l, respectively. The mean serum acetaminophen levels were higher in group IIB (120 µg/ml) than in group IB (87 µg/ml). The gastric retention values were significantly higher in group IIB than in group IIA for all three test meals: saline, 51 vs 35 percent; glucose, 52 vs 38 percent and mayonnaise, 51 vs 29 percent(median values). The correlation between gastric retention and AST levels was significant (P<0.05) for group IIB for the three test meals: r = 0.73, 0.67 and 0.68 for saline, glucose and mayonnaise, respectively. We conclude that GE is altered in rats with hepatic lesions induced by acetaminophen, and that these alterations may be related to the liver cell necrosis caused by the drug

Daño hepático por acetaminofeno: caso clínico / Hepatic damage due to acetaminophen: a clinical case

Se presenta el caso de una paciente de 27 años de edad, con el antecedente de ingesta excesiva de fármacos en forma voluntaria. Por sospecha de corresponder a una dosis alta de acetaminofeno, se evalúa con niveles plasmáticos de la droga (que confirman la ingesta) enzimas hepáticas y pruebas de coagulación, mostrando evolución rápida y progresiva al daño hepático agudo. No se obtuvo restos de fármacos del lavado gástrico efectuando al ingreso y no se pudo contar con el antídoto específico (n-acetilcisteína). La paciente evolucionó inicialmente soporosa, y luego con sensibilidad en hipocondrio derecho e ictericia. Se usó fitonodiona IM y plasma fresco congelado para corregir las alteraciones de coagulación, hidratación parenteral, ranitidina EV, dieta cero por boca. Se observó paulatina recuperación. Se revisa el mecanismo de daño hepático del acetaminofeno y se comentan las posibilidades terapéuticas