Theophylline metabolism in patients with hepatosplenic mansoniasis and cirrhosis

Untargeted serum metabolomic profiling for early detection of Schistosoma mekongi infection in mouse model

Mekong schistosomiasis is a parasitic disease caused by blood flukes in the Lao People’s Democratic Republic and in Cambodia. The standard method for diagnosis of schistosomiasis is detection of parasite eggs from patient samples. However, this method is not sufficient to detect asymptomatic patients, low egg numbers, or early infection. Therefore, diagnostic methods with higher sensitivity at the early stage of the disease are needed to fill this gap. The aim of this study was to identify potential biomarkers of early schistosomiasis using an untargeted metabolomics approach. Serum of uninfected and S. mekongi-infected mice was collected at 2, 4, and 8 weeks post-infection. Samples were extracted for metabolites and analyzed with a liquid chromatography-tandem mass spectrometer. Metabolites were annotated with the MS-DIAL platform and analyzed with Metaboanalyst bioinformatic tools. Multivariate analysis distinguished between metabolites from the different experimental conditions. Biomarker screening was performed using three methods: correlation coefficient analysis; feature important detection with a random forest algorithm; and receiver operating characteristic (ROC) curve analysis. Three compounds were identified as potential biomarkers at the early stage of the disease: heptadecanoyl ethanolamide; picrotin; and theophylline. The levels of these three compounds changed significantly during early-stage infection, and therefore these molecules may be promising schistosomiasis markers. These findings may help to improve early diagnosis of schistosomiasis, thus reducing the burden on patients and limiting spread of the disease in endemic areas.

Differences in Theophylline Clearance Between Patients With Chronic Hepatitis and Those With Liver Cirrhosis

BACKGROUND

Theophylline, a xanthine derivative drug, is used for the treatment of respiratory diseases, such as asthma, and is primarily eliminated by hepatic metabolism. There is marked interindividual variability in theophylline clearance. Therefore, the aim of this study was to evaluate the influence of chronic hepatitis (CH), liver cirrhosis (LC), and other covariates on theophylline clearance by population pharmacokinetic (PPK) analysis.

METHODS

The authors retrospectively obtained 496 trough concentrations of theophylline at steady state from 226 adult patients with bronchial asthma. The liver functions of the patients were classified into 3 categories: normal hepatic function, CH, and LC. The PPK analysis was performed using the NONMEM program. CH, LC, age, smoking status, coadministration of clarithromycin (CAM), and sex were considered as covariates that affected theophylline clearance.

RESULTS

Theophylline clearance (CL/F per kg) was significantly influenced by CH, LC, smoking, and CAM. The final model of theophylline clearance was as follows: CL/F (L/h·kg) = 0.0484 × 1.40 × 0.861 × 0.889 × 0.557. Smoking is a well-known factor that markedly enhances CL/F through the induction of CYP1A enzymes, whereas CAM has been reported to inhibit CYP3A4. The final model for hepatic function showed that CL/F in CH and LC patients was 0.043 and 0.027 L/h/kg, respectively, and it was lower than that in patients with normal hepatic function. As theophylline clearance depends on intrinsic hepatic clearance, lower CL/F in patients with LC than in those with CH may be due to a decrease in the metabolic enzymatic capability of LC patients.

CONCLUSIONS

Differences exist in theophylline clearance between CH and LC patients as per the PPK analysis.

A review of the pharmacokinetic implications of schistosomiasis

Schistosomiasis is a common parasitic disease, with over 230 million people requiring treatment annually. The worldwide increase in medication access poses risks for patients living in regions endemic for schistosomiasis because of the potential impact of pharmacokinetic changes on clinical outcomes. Thus, the objective of this review is to summarize and evaluate the published literature reporting pharmacokinetic parameters of medications in patients with schistosomiasis and to assess associated clinical implications. Thirteen articles that described the pharmacokinetics of a total of 9 different medications (cefoperazone, propranolol, praziquantel, theophylline, metronidazole, acetaminophen/paracetamol, antipyrine, oxamniquine, and oral contraceptives) in patients with schistosomiasis were included in the review. The major finding is that pharmacokinetic changes occur in patients infected with schistosomiasis but to varying degrees depending on the extent of disease (e.g., varying stages of fibrosis, with or without signs and/or symptoms of liver disease) and medication being administered. Affected patients may consequently be at risk of adverse clinical outcomes. In general, drugs with high extraction ratios demonstrate increased bioavailability in patients with schistosomiasis compared to controls. For example, propranolol and praziquantel, respectively, show an association with increased clinical and toxic effects in patients with schistosomiasis. Conversely, the pharmacokinetics of low hepatic clearance drugs (such as metronidazole and oxamniquine) are largely unchanged unless patients present with liver disease (as in the case of antipyrine, the prototypical low clearance drug). Limitations of studies included the very small numbers of patients, being primarily single-dose studies, and the high inter-individual variability. Future clinical studies should include pharmacokinetic outcomes to further clarify dosing and administration strategies for target medications, especially those that primarily undergo metabolism and are associated with significant adverse effects. Until the results of these future studies are available, clinicians should be acutely aware of complications from schistosomiasis and carefully screen patients for signs and symptoms of liver disease prior to prescribing, dispensing, or administering potentially harmful medications.

A semi-mechanistic model to predict the effects of liver cirrhosis on drug clearance

BACKGROUND AND OBJECTIVE

Liver cirrhosis is characterized by a decrease in functional hepatocytes, lowered circulating levels of plasma proteins and alterations in blood flow due to the development of portacaval shunts. Depending on the interplay between these parameters and the characteristics of an administered drug, varying degrees of impaired systemic clearance and first-pass metabolism are anticipated. The Simcyp Population-based ADME Simulator has already been used successfully to incorporate genetic, physiological and demographic attributes of certain subgroups within healthy populations into in vitro-in vivo extrapolation (IVIVE) of xenobiotic clearance. The objective of this study was to extend population models to predict systemic and oral drug clearance in relation to the severity of liver cirrhosis.

METHODS

Information on demographics, changes in hepatic blood flow, cytochrome P450 enzymes, liver size, plasma protein binding and renal function was incorporated into three separate population libraries. The latter corresponded to Child-Pugh scores A (mild), B (moderate) and C (severe) liver cirrhosis. These libraries, together with mechanistic IVIVE within the Simcyp Simulator, were used to predict the clearance of intravenous and oral midazolam, oral caffeine, intravenous and oral theophylline, intravenous and oral metoprolol, oral nifedipine, oral quinidine, oral diclofenac, oral sildenafil, and intravenous and oral omeprazole. The simulated patients matched the clinical studies as closely as possible with regard to demographics and Child-Pugh scores. Predicted clearance values in both healthy control and liver cirrhosis populations were compared with observed values, as were the fold increases in clearance values between these populations.

RESULTS

There was good agreement (lack of statistically significant difference, two-tailed paired t-test) between observed and predicted clearance ratios, with the exception of those for two studies of intravenous omeprazole. Predicted clearance ratios were within 0.8- to 1.25-fold of observed ratios in 65% of cases (range 0.34- to 2.5-fold).

CONCLUSION

The various drugs that were studied showed different changes in clearance in relation to disease severity, and a 'one size fits all' solution does not exist without considering the multiple sources of the changes. Predictions of the effects of liver cirrhosis on drug clearance are of potential value in the design of clinical studies during drug development and, clinically, in the assessment of likely dosage adjustment.

Biotransformation of theophylline in cirrhotic rats induced by biliary obstruction

The object of this work was to study the pharmacokinetic differences and the cause of these differences in cirrhotic rats induced by biliary obstruction when aminophylline (8 mg/kg as theophylline, i.v.) was administered. The concentrations of theophylline and its major metabolite (1,3-dimethyluric acid) in plasma were determined by HPLC. In addition, formation of 1,3-dimethyluric acid from theophylline in microsomes and the changes in the activity of drug metabolizing enzymes, which are suggested to be involved in theophylline metabolism, were determined. In cirrhotic rats, the systemic clearance of theophylline was reduced to 30% of the control value while AUC (area under the plasma concentration-time curve) and (t1/2)beta were increased 1.3 fold and 3.5 fold, respectively. The formation of 1,3-dimethyluric acid was decreased to 30% of the control value in microsomes of cirrhotic rat liver. In cirrhotic rat liver, activities of aniline hydroxylase (CYP2E1 related), erythromycin-N-demethylase (CYP3A related), and methoxyresorufin-O-demethylase (CYP1A2 related), which were reported to be related with theophylline metabolism, were decreased to 67%, 53%, and 76% that of normal rat liver, respectively. From the results, it can be concluded that in cirrhotic rats induced by biliary obstruction, the total body clearance of theophylline is markedly reduced and it may be due to decreased activity of drug metabolizing enzymes in liver.