Pharmacokinetics Of Theophylline Research Articles

Identification of the perpetrator imperatorin in Xin-yi-san-theophylline interaction: observed and predicted herb-drug interaction in rats.

Theophylline is a bronchodilator with a narrow therapeutic index and primarily metabolised by cytochrome P450 (CYP) 1A2. Xin-yi-san (XYS) is a herbal formula frequently used to ameliorate nasal inflammation. This study aimed to investigate the effects of XYS and its ingredient, imperatorin, on theophylline pharmacokinetics in rats. The kinetics of XYS- and imperatorin-mediated inhibition of theophylline oxidation were determined. Pharmacokinetics of theophylline were analysed. Comparisons were made with the CYP1A2 inhibitor, fluvoxamine. XYS extract and its ingredient, imperatorin, non-competitively inhibited theophylline oxidation. Fluvoxamine (50 and 100 mg/kg) and XYS (0.5 and 0.9 g/kg) significantly prolonged the time to reach the maximum plasma concentration (tmax) of theophylline by 3-10 fold. In a dose-dependent manner, XYS and imperatorin (0.1-10 mg/kg) treatments significantly decreased theophylline clearance by 27-33% and 19-56%, respectively. XYS (0.9 g/kg) and imperatorin (10 mg/kg) significantly prolonged theophylline elimination half-life by 29% and 142%, respectively. Compared with the increase (51-112%) in the area under curve (AUC) of theophylline by fluvoxamine, the increase (27-57%) by XYS was moderate. XYS decreased theophylline clearance primarily through imperatorin-suppressed theophylline oxidation. Further human studies are essential for the dose adjustment in the co-medication regimen.

Application of a Physiologically Based Pharmacokinetic Approach to Predict Theophylline Pharmacokinetics Using Virtual Non-Pregnant, Pregnant, Fetal, Breast-Feeding, and Neonatal Populations.

Perinatal pharmacology is influenced by a myriad of physiological variables that are changing dynamically. The influence of these covariates has not been assessed systemically. The objective of this work was to use theophylline as a model drug and to predict its pharmacokinetics before, during (including prediction of the umbilical cord level), and after pregnancy as well as in milk (after single and multiple doses) and in neonates using a physiological-based pharmacokinetic (PBPK) model. Neonatal theophylline exposure from milk consumption was projected in both normal term and preterm subjects. Predicted infant daily doses were calculated using theophylline average and maximum concentration in the milk as well as an estimate of milk consumption. Predicted concentrations and parameters from the PBPK model were compared to the observed data. PBPK predicted theophylline concentrations in non-pregnant and pregnant populations at different gestational weeks were within 2-fold of the observations and the observed concentrations fell within the 5th−95th prediction interval from the PBPK simulations. The PBPK model predicted an average cord-to-maternal plasma ratio of 1.0, which also agrees well with experimental observations. Predicted postpartum theophylline concentration profiles in milk were also in good agreement with observations with a predicted milk-to-plasma ratio of 0.68. For an infant of 2 kg consuming 150 ml of milk per day, the lactation model predicted a relative infant dose (RID) of 12 and 17% using predicted average (Cavg,ss) and maximum (Cmax,ss) concentration in milk at steady state. The maximum RID of 17% corresponds to an absolute infant daily dose of 1.4 ± 0.5 mg/kg/day. This dose, when administered as 0.233 mg/kg every 4 h, to resemble breastfeeding frequency, resulted in plasma concentrations as high as 3.9 (1.9–6.8) mg/L and 2.8 (1.3–5.3) (5th−95th percentiles) on day 7 in preterm (32 GW) and full-term neonatal populations.

Pharmacokinetics of a 503B outsourcing facility-produced theophylline in dogs.

Theophylline is an important drug for treatment of canine chronic bronchitis and bradyarrhythmias, but new products require validation since pharmacokinetics in dogs can vary by formulation. A new, 503B outsourcing facility-produced theophylline product (OFT) is available for veterinary use. Outsourcing facilities have many advantages over traditional compounding sources including current good manufacturing practice compliance. The purpose of this study was to establish the pharmacokinetics of OFT in dogs. Eight healthy dogs received 11 mg/kg intravenous aminophylline and 10 mg/kg oral OFT followed by serial blood sampling in a two-way, randomized, crossover design with 7-day washout. Plasma theophylline concentrations were quantified by liquid chromatography-mass spectrometry. Bioavailability, maximum concentration, time to maximum concentration, half-life and area under the curve were: 97 ± 10%, 7.13 ± 0.71 μg/mL, 10.50 ± 2.07 h, 9.20 ± 2.87 h, and 141 ± 37.6 μg*h/mL, respectively. Steady-state predictions supported twice daily dosing of the OFT, but specific dosage recommendations are hindered by lack of a canine-specific therapeutic range for plasma theophylline concentration. These findings suggest that the OFT is well absorbed and can likely be dosed twice daily in dogs, but future pharmacodynamic and clinical studies are needed to establish a definitive therapeutic range for theophylline in this species.

Alteration of the Pharmacokinetics of Theophylline by Paullinia cupana Kunth in Rats

Aims: Paullinia cupana Kunth has been popularly used to prepare different beverages by the Amazonian inhabitants for a long time ago mainly due to its stimulant properties. Although the utilization of this herbal drug has been increasing lately, little is known regarding the possibility of drug interactions. Therefore, this research tried to investigate the effects of the aqueous extract of P. cupana on the pharmacokinetics of theophylline (TPH), a CYP1A marker in rats.
 Methodology: The extract was prepared according to the popular recipe and subjects received different once daily doses of extract (vehicle, 82.1 mg/Kg and 821 mg/Kg) by oral gavage during two weeks. Non-compartimental analysis was carried out to obtain the pharmacokinetic parameters.
 Results: Animals treated with P. cupana (AUC: 1,197.2 ± 284.4 and 346.6 ± 37.0 µg.h/mL for 82.1 and 821 mg/Kg, respectively) had lower exposition to TPH than controls (3,539.48 ± 278.4 µg.h/mL). On the other hand, drug clearance was higher in treated subjects (2.44 ± 0.4 and 7.27 ± 0.7 L/h/kg for 82.1 and 821 mg/Kg, respectively) than controls (0.71 ± 0.0 L/h/kg).
 Conclusion: Therefore, the multiple oral administration of an aqueous extract of P. cupana caused a significant effect on the pharmacokinetics of TPH in rats.

Herb–drug interaction studies of ethanolic extract of Cassia occidentalis L. coadministered with acetaminophen, theophylline, omeprazole, methotrexate and methylprednisolone

BackgroundTraditionally Cassia occidentalis L. extract is used for the treatment of several diseases including fever, bone diseases, fracture, kidney and digestive diseases. Ethanolic extract of Cassia occidentalis L. (EECO) is being developed as a phytopharmaceutical for corticosteroid-induced osteoporosis. PurposeThis study was aimed to investigate the effect of EECO on the pharmacokinetics of acetaminophen (ACET), theophylline (THEO), omeprazole (OMEP), methotrexate (MTX), and methylprednisolone (MP). MethodsInteraction studies were performed in Sprague Dawley (SD) rats. ACET (100 mg/kg), THEO (25 mg/kg), OMEP (40 mg/kg), MTX (5 mg/kg), or MP (5 mg/kg) was administered with and without EECO (250 mg/kg) separately. ResultsThe LLOQ of all analytes was 10 ng/mL except for OMEP (1 ng/mL) and r2 > 0.994. The intra-day and inter-day RSD (%) were ≤12.13 and accuracy (%) was between 89.19 and 112.67 at four QC levels. Our results suggested that EECO caused interaction when coadministered with ACET, MTX and MP. No changes were found in the bioavailability of THEO and OMEP. EECO had inhibitory effects on CYP1A2, CYP2C9 and CYP3A4. ConclusionsBased on these results, dose adjustment may be required when ACET, MP and MTX are coadministered with EECO. These results would be useful for phase 1 clinical trial of EECO.

Investigating the Role of Altered Systemic Albumin Concentration on the Disposition of Theophylline in Adult and Pediatric Patients with Asthma by Using the Physiologically Based Pharmacokinetic Approach.

Theophylline is commonly used for the treatment of asthma and has a low hepatic clearance. The changes in plasma albumin concentration occurring in asthma may affect the exposure of theophylline. The aim of the presented work was to predict theophylline pharmacokinetics (PK) after incorporating the changes in plasma albumin concentration occurring in patients with asthma into a physiologically based pharmacokinetic (PBPK) model to see whether these changes can affect the systemic theophylline concentrations in asthma. The PBPK model was developed following a systematic model building approach using Simcyp. The predictions were performed initially in healthy adults after intravenous and oral drug administration. Only when the developed adult PBPK model had adequately predicted theophylline PK in healthy adults, the changes in plasma albumin concentrations were incorporated into the model for predicting drug exposure in patients with asthma. After evaluation of the developed model in the adult population, it was scaled to children on physiologic basis. The model evaluation was performed by using visual predictive checks and comparison of ratio of observed and predicted (Robs/Pre) PK parameters along with their 2-fold error range. The developed PBPK model has effectively described theophylline PK in both healthy and diseased populations, as Robs/Pre for all the PK parameters were within the 2-fold error limit. The predictions in patients with asthma showed that there were no significant changes in PK parameters after incorporating the changes in serum albumin concentration. The mechanistic nature of the developed asthma-PBPK model can facilitate its extension to other drugs. SIGNIFICANCE STATEMENT: Exposure of a low hepatic clearance drug like theophylline may be susceptible to plasma albumin concentration changes that occur in asthma. These changes in systemic albumin concentrations can be incorporated into a physiologically based pharmacokinetic model to predict theophylline pharmacokinetics in adult and pediatric asthma populations. The presented work is focused on predicting theophylline absorption, distribution, metabolism, and elimination in adult and pediatric asthma populations after incorporating reported changes in serum albumin concentrations to see their impact on the systemic theophylline concentrations.

Bioanalytical Study of the Effect of Lycopene on the Pharmacokinetics of Theophylline in Rats

Lycopene, a natural pigment, was reported to have a modulatory effect on cytochrome P450, hence, metabolic clearance of some drugs. This research is concerned with studying the influence of lycopene on the pharmacokinetics of theophylline, a drug with a narrow therapeutic index. Lycopene (10 mg/kg) was intraperitoneally given to rats for eight consecutive days and on the eighth day of treatment, theophylline (5 mg/kg) was intravenously administered. Blood samples were withdrawn from rats at various time periods, treated and analyzed using HPLC. The HPLC method was based on isocratic elution of theophylline and caffeine as internal standard on ZORBAX Eclipse plus C8 column using a mobile phase consisting of water and methanol (80:20, v/v) at a flow rate of 1 mL min-1. Statistical analysis of the pharmacokinetic data using Paired t-test showed a significant decrease in AUC0–t and AUC0-∞ (about 22.140 and 23.824%, respectively,P < 0.05) and a significant increase in Vd and CL (1.28- and 1.40-fold, respectively, P < 0.05) of theophylline administered to rats pretreated with lycopene. Treatment with lycopene has a significant effect on the metabolic clearance and pharmacokinetics of theophylline in rats.

Inhibition of Rat CYP1A2 and CYP2C11 by Honokiol, a Component of Traditional Chinese Medicine.

Honokiol, a major constituent isolated from Magnolia officinalis, is regarded as a phytochemical marker and bioactive substance present in many traditional Chinese medicines. However, the effect of honokiol on cytochrome P450 (CYP) has not been thoroughly investigated. The aim of this study was to investigate the effect of honokiol on CYP1A2 and CYP2C11 in vitro and in vivo. The effect of honokiol on CYP1A2 and CYP2C11 was investigated with rat liver microsomes (RLMs) by measuring phenacetin and tolbutamide metabolism (probe drugs for CYP1A2 and CYP2C11, respectively), and then explored in vivo by measuring the effect of honokiol (2.5 and 5mg/kg, intravenous injection) on the pharmacokinetics of theophylline and tolbutamide (probe drugs for CYP1A2 and CYP2C11, respectively) in rats in vivo. Honokiol inhibited the formation of acetaminophen from phenacetin and 4-hydroxytolbutamide from tolbutamide in RLMs, with inhibition constant (Ki) values of 1.6μM and 16.5μM, respectively. In vivo, honokiol (2.5 or 5.0mg/kg) increased the half-life (t1/2) of theophylline by 40.9% and 119.9%, decreased the clearance (CL) by 23.8% and 42.9%, and increased the area under the curve (AUC) by 41.3% and 83.4%, respectively. Similarly, the t1/2 of tolbutamide increased by 25.5% and 33.8%, the CL decreased by 14.3% and 19.1%, and the AUC increased by 19.2% and 25.7%, respectively. The inhibition of CYP1A2 by honokiol is greater than the inhibition of CYP2C11. The changes in the pharmacokinetics of theophylline and tolbutamide in rats treated with honokiol are due to the inhibition of CYP1A2 and CYP2C11 activity in a dose-dependent manner.

Impact of Ethnicity-Specific Hepatic Microsomal Scaling Factor, Liver Weight, and Cytochrome P450 (CYP) 1A2 Content on Physiologically Based Prediction of CYP1A2-Mediated Pharmacokinetics in Young and Elderly Chinese Adults.

The vast majority of physiological and biological data required for physiologically based predictions are primarily available in Caucasians rather than other ethnic populations, which leads to a lack of confidence in the application of physiologically based pharmacokinetic (PBPK) modeling for ethnicity-specific prediction of pharmacokinetics in the Chinese population. In this study we recalibrate the system parameters of Chinese-specific PBPK modeling and explore for the first time the relative importance of ethnicity-specific microsomal protein per gram of liver (MPPGL), liver weight, and cytochrome P450 (CYP) 1A2 abundance to the projection of drug disposition mediated by CYP1A2 in young and elderly Chinese adults. Chinese MPPGL levels and associated variability were parameterized and incorporated for the first time into ethnicity-specific PBPK models for the Chinese adults. Parameterization of Chinese liver weights was also recalibrated on the basis of autopsy data from Chinese individuals (n = 4081) across the entire adult age range. Uncertainty surrounding the Chinese-specific CYP1A2 content has also been explored and clarified by conducting ethnicity-related PBPK simulations under different scenarios. Various ethnicity-related or 'what-if' scenarios for PBPK modeling were implemented to assess the predictive performance and explore the relative importance of ethnicity-specific MPPGL and liver weight to the projection of drug disposition mediated by CYP1A2 in terms of two typical CYP1A2 substrates, caffeine and theophylline, in young and elderly Chinese adults by comparing the predicted concentration-time data and associated pharmacokinetic parameter estimates with observations. Compared with 0.85, the liver scalar of 0.9 generally produced more accurate liver weight levels in virtual Chinese peers. Additionally, simulated MPPGL levels on the basis of Caucasian data were not able to reflect the age-independent pattern observed in Chinese adults, dissimilar to that on the basis of Chinese-specific adult MPPGL data. The modeling Scenarios A and B provided similar predictions for theophylline pharmacokinetics in young Chinese adults across different age groups, while Scenario B provided the most accurate prediction for theophylline pharmacokinetics in elderly Chinese adults. However, the use of a stratified value of CYP1A2 content derived from a Han Chinese cohort with a small sample size instead of the pooled value of all Chinese cohorts involved regardless of Chinese sub-ethnicity resulted in inadequate prediction of CYP1A2-mediated pharmacokinetics in terms of caffeine and theophylline in either young or elderly Chinese subjects. Additionally, the impact of ethnic-specific MPPGL on predictive accuracy of theophylline pharmacokinetics in elderly Chinese subjects is more evident than that of liver weight. We provided quantitative information pertaining to Chinese-specific levels of liver weight and MPPGL, and recalibrated these system parameters for PBPK modeling for young and elderly Chinese subjects. Uncertainty surrounding the Chinese-specific CYP1A2 content has also been clarified. PBPK modeling based on the recalibrated system parameters can accurately simulate CYP1A2-mediated pharmacokinetics in both young and elderly Chinese adults, particularly in elderly individuals.

Population pharmacokinetics of theophylline in adult Chinese patients with asthma and chronic obstructive pulmonary disease.

Background Theophylline has a narrow therapeutic range and large interindividual variabilityin blood levels, so a thorough understanding of its pharmacokinetic characteristics is essential. Population pharmacokinetic (PPK) approaches could achieve it and many PPK studies of theophylline have been reported in infants. However, none was conducted in Chinese adults and none has explored the effect of CYP1A2 genotypes on the PPK characteristics of theophylline in adults. Objective To evaluate the PPK characteristics of theophylline and to assess the possible influence of covariates, including CYP1A2 genotypes, on theophylline clearance in Chinese adult patients. Setting The study is conducted at the department of respiration in Zhujiang Hospital, Guangzhou, China. Methods Theophylline concentrations were obtained from eligible patients and were measured by high performance liquid chromatography. The polymorphisms of - 3860G > A, - 163C > A, C5347T (CYP1A2*1B) and G-3113A were genotyped using a direct sequencing method. Then, CYP1A2 genotypes, age, fat-free mass (FFM) and other covariates were used to develop a PPK model by NONMEM software. Bootstrap analysis was used to asses the accuracy and prediction of the PPK model. Main outcome measure The concentration and clearance of theophylline. Results A total of 134 theophylline concentrations from 95 patients were obtained. The final model was as follows: CL/F(L/h) = 4.530 × (FFM/56.1)0.75× 0.713CYP1A2*1B, the inter-individual variability in clearance/bioavailability (CL/F) was 44.0%, and the residual variability was 9.8%. The final model was proved to be reliable by bootstrap analysis. Conclusion Theophylline clearance was significantly associated with FFM and CYP1A2*1B genotypes in Chinese adult patients.

Dr Elliot F. Ellis: Initiating personalized asthma management in children

Abstract Elliot F. Ellis is indeed a giant in the field of allergy and immunology. From his leadership role in developing a pediatric allergy and immunology fellowship at National Jewish Health and his seminal work in theophylline pharmacokinetics, he trained many excellent clinicians and researchers. He assumed the role of Chair of Pediatrics at the Children's Hospital of Buffalo in 1974 and transformed that training program in pediatrics to a top-rated program in the country along with his own training program in allergy and immunology. He co-edited the first edition of Allergy Principles and Practice with Elliott Middleton, Jr., MD and Charles E. Reed, MD. His clinical research provided the building blocks for personalized medicine in asthma, especially as it pertains to children.

Predictive Performance of Physiologically Based Pharmacokinetic (PBPK) Modeling of Drugs Extensively Metabolized by Major Cytochrome P450s in Children.

The accuracy of physiologically based pharmacokinetic (PBPK) model prediction in children, especially those younger than 2 years old, has not been systematically evaluated. The aim of this study was to characterize the pediatric predictive performance of the PBPK approach for 10 drugs extensively metabolized by CYP1A2 (theophylline), CYP2C8 (desloratidine, montelukast), CYP2C9 (diclofenac), CYP2C19 (esomeprazole, lansoprazole), CYP2D6 (tramadol), and CYP3A4 (itraconazole, ondansetron, sufentanil). Model performance in children was evaluated by comparing simulated plasma concentration-time profiles with observed clinical results for each drug and age group. PBPK models reasonably predicted the pharmacokinetics of desloratadine, diclofenac, itraconazole, lansoprazole, montelukast, ondansetron, sufentanil, theophylline, and tramadol across all age groups. Collectively, 58 out of 67 predictions were within 2-fold and 43 out of 67 predictions within 1.5-fold of observed values. Developed PBPK models can reasonably predict exposure in children age 1 month and older for an array of predominantly CYP metabolized drugs.

Theophylline: a review of population pharmacokinetic analyses.

Numerous population pharmacokinetic studies of theophylline have been conducted in paediatric and adult patients. The purpose of this review was to summarize the published studies concerning population pharmacokinetics of theophylline in patients of different ages and discuss factors that might cause the large variability in the pharmacokinetics of theophylline. A literature search was conducted in PubMed using the following keywords: 'theophylline', 'population pharmacokinetic(s)' and 'nonlinear mixed effect model'. Additionally, the relevant references listed in the retrieved articles were manually reviewed. All of the studies that reported the population pharmacokinetics of theophylline in humans were included in this review. However, articles were excluded if they were not written in English. Sixteen articles were included in this review. Among them, 11 were conducted on paediatric patients, and five were conducted on adults. A one-compartment model with first-order elimination was employed in most of the included articles. A nonlinear mixed effect modelling approach (NONMEM) was the most commonly used software to develop a population pharmacokinetic model. Body weight and age (post-conceptional age and post-natal age) were the most important factors associated with the clearance (CL) of theophylline in paediatric patients. Body weight (ideal body weight and lean body mass), age and smoking status were most frequently used to estimate the CL of theophylline in adults. The median (range) estimate values of CL for paediatric and adult patients were 0·062 (0·0056-0·0949) L/h/kg and 0·053 (0·0493-0·0517) L/h/kg, respectively. The median values of the interindividual variability of CL were 33·5% in adults and 25·8% in paediatric patients. The mean values of the residual variability were 21% in paediatric patients and 14·3% in adults. This review concludes that body weight and age were the most important factors associated with the clearance of theophylline in paediatric patients. Body weight, age and smoking were most frequently used to estimate the clearance of theophylline in adults. Future studies are warranted to detect the influence of new factors, such as cytochrome P450 (CYP) 1A2 gene polymorphisms, on the pharmacokinetics of theophylline because some pharmacokinetic variability was not fully explained.

Theophylline Population Pharmacokinetics and Dosing in Children Following Congenital Heart Surgery With Cardiopulmonary Bypass.

Children undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) frequently develop acute kidney injury due to renal ischemia. Theophylline, which improves renal perfusion via adenosine receptor inhibition, is a potential targeted therapy. However, children undergoing cardiac surgery and CPB commonly have alterations in drug pharmacokinetics. To help understand optimal aminophylline (salt formulation of theophylline) dosing strategies in this population, a population-based pharmacokinetic model was developed using nonlinear mixed-effects modeling (NONMEM) from 71 children (median age 5 months; 90% range 1 week to 10 years) who underwent cardiac surgery requiring CPB and received aminophylline as part of a previous randomized controlled trial. A 1-compartment model with linear elimination adequately described the pharmacokinetics of theophylline. Weight scaled via allometry was a significant predictor of clearance and volume. In addition, allometric scaled clearance increased with age implemented as a power maturation function. Compared to prior reports in noncardiac children, theophylline clearance was markedly reduced across age. In the final population pharmacokinetic model, optimized empiric dosing regimens were developed via Monte Carlo simulations. Doses 50% to 75% lower than those recommended in noncardiac children were needed to achieve target serum concentrations of 5 to 10 mg/L.

Application of a Physiologically Based Pharmacokinetic Model to Study Theophylline Metabolism and Its Interactions With Ciprofloxacin and Caffeine

Theophylline is a commonly used bronchodilator. However, due to its narrow therapeutic range, moderate elevation of serum concentration can result in adverse drug reactions (ADRs). ADRs occur because of interhuman pharmacokinetic variability and interactions with coprescribed medicines. We developed a physiologically based pharmacokinetic (PBPK) model of theophylline, caffeine, and ciprofloxacin metabolisms to: examine theophylline pharmacokinetic variability, and predict population-level outcomes of drug-drug interactions (DDIs). A simulation-based equation for personalized dosing of theophylline was derived. Simulations of DDI show that calculated personalized doses are safe even after cotreatment with large doses of strong inhibitors. Simulations of adult populations indicate that the elderly are most susceptible to ADRs stemming from theophylline-ciprofloxacin and theophylline-caffeine interactions. Females, especially Asians, due to their smaller average size, are more susceptible to DDI-induced ADRs following typical dosing practices. Our simulations also show that the higher adipose and lower muscle fractions in females significantly alter the pharmacokinetics of theophylline or ciprofloxacin.

Pharmacokinetic interaction of Acacia catechu with CYP1A substrate theophylline in rabbits

ObjectiveTo investigate the effect of black catechu (BC) on the pharmacokinetics of theophylline (CYP1A2 substrate, with narrow therapeutic index) in rabbits. MethodsIn the present investigation the effect of BC on the pharmacokinetics of theophylline, a CYP1A2 substrate was determined. In the study, BC (264 mg/kg, p. o.) or saline (control group) was given to rabbits for 7 consecutive days and on the 8th day theophylline (16 mg/kg) was administered orally one hour after BC or saline treatment. Blood samples were withdrawn at different time intervals (0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24 and 36 h) from the marginal ear vein. ResultsThe pretreatment of rabbits with BC resulted in a significant increase in maximum blood concentration, time of peak concentration and area under the concentration time profile curve until last observation which was about 41.32%, 35.71% and 15.03%, respectively. While decreases in clearance, volume of distribution, and half-life were observed. It is suggested that BC pretreatment decreases the CYP1A metabolic activity leading to increase in bioavailability and decrease in oral clearance of theophylline, which may be due to inhibition of CYP1A. ConclusionBC can significantly alter theophylline pharmacokinetics in vivo possibly due to inhibition of CYP1A and P-glycoprotein activity. Based on these results, precaution should be exercised when administering BC with CYP1A substrate.

A simple HPLC-UV method for the quantification of theophylline in rabbit plasma and its pharmacokinetic application.

A simple, precise and accurate high-performance liquid chromatography-ultraviolet method was developed and validated for the quantification of theophylline in rabbit plasma using hydroxyethyl theophylline as an internal standard. Separation was performed on Waters(®) C18 column (µBondapak™ 5 µm, 150 × 3.9 mm) using a mobile phase consisting of water-acetonitrile (96:4 v/v) at a flow rate of 1 mL/min. Validation of the method was performed in order to demonstrate its selectivity, linearity, precision, accuracy and stability. The calibration curves of theophylline were linear over a concentration range of 0.1-25 µg/mL. The within- and between-day coefficient of variation (CV) were <10%. The extraction recoveries of theophylline at the three levels of quality control samples were 63.1, 69.4 and 69.7%. The method was rapid with retention time of theophylline and the internal standard observed at ∼5.2 and 6.5 min, respectively. The developed method was applied successfully for studying the pharmacokinetics of theophylline in rabbits.

Theophylline Pharmacokinetics in Foetal Sheep: Maternal Metabolic Capacity is the Principal Driver.

Understanding theophylline pharmacokinetics (PK) in the foetus is essential to prevent in utero toxicity and optimize prophylactic therapies. Previous studies in pregnancy have been obfuscated by maternal dosing and inadequate sampling in the foetus; both render modelling of foetal PK difficult. Six ewes carrying singleton foetuses received theophylline (60mg) into the foetal jugular vein. Blood samples were drawn from the foetus and ewe over 36hr. Serum concentrations were measured. Maternal and foetal pharmacokinetic parameters were estimated. Foetal non-compartmental pharmacokinetic parameters were as follows: half-life 7.37±1.22hr; volume of distribution 44.62±11.45L; area under the curve 14.82±2.71hr/(μg/mL); and clearance 4.15±0.70L/hr. Rapid theophylline distribution across the placenta was observed. Maternal non-compartmental pharmacokinetic parameters were as follows: half-life 6.54±2.44hr; volume of distribution 32.48±9.99L; area under the curve 16.28±4.53hr/(μg/mL); and clearance 3.69±1.47L/hr. Foetal and ewe serum concentration-time profiles were fit together into a 3-compartment population pharmacokinetic model, and parameters were as follows: central volume 1.38±0.11L; 2nd peripheral compartment volume 3.11±0.29L; 3rd peripheral compartment volume 60.14±6.02L; elimination clearance 9.89±0.90L/hr; distribution clearance between central and 2nd compartment 30.87±2.31L/hr; and distribution clearance between 2nd and 3rd compartments 13.89±1.11L/hr. Cytochrome P4501A expression was robust in maternal liver; negligible activities were observed in placenta, foetal liver and foetal kidney. In vitro protein binding of theophylline was 30% lower in foetal serum compared to maternal serum (29.7±4.4 versus 42.0±3.6%-bound). Free concentrations were lower in the foetus than in the ewe, suggesting active transport across placenta. In summary, foetal clearance of theophylline is attributable to rapid distribution into the maternal circulation across the placenta followed by greater maternal protein binding and metabolic activity.

Effects of fenugreek, garden cress, and black seed on theophylline pharmacokinetics in beagle dogs

Context: Herb–drug interactions are a serious problem especially for drugs with a narrow therapeutic index, taking into consideration that herbal medicines are commonly used in various parts of the world.Objective: The present study investigates the effect of fenugreek, garden cress, and black seed on the pharmacokinetics of theophylline in beagle dogs.Materials and methods: Beagle dogs received theophylline (200 mg) orally and blood samples were withdrawn at different time intervals (0.33, 0.66, 1.0, 1.5, 2, 3, 4, 6, 8, 12, 24, and 30 h). After a suitable washout period, each herb was given orally at doses of 25, 7.5, and 2.5 g, twice daily for 7 d. On the eighth day, theophylline was re-administrated orally and blood samples were collected. Plasma concentrations of theophylline were determined using HPLC and pharmacokinetic parameters were calculated using a non-compartmental analysis.Results: Treatment with fenugreek (25 g, orally) lead to a decrease in Cmax and AUC0–t of theophylline of about 28% (p < 0.05) and 22% (p < 0.05), respectively, with no significant changes in T1/2λ compared with the baseline values. Garden cress caused a decrease in Cmax to a lesser extent and delayed Tmax of theophylline (2.10 ± 0.24 h versus 3.40 ± 0.74 h), while AUC0–∞ increased by 37.44%. No significant effect was observed for the black seed treatment on theophylline disposition as measured by Cmax, Tmax, AUC0–∞, and CL/F.Discussion and conclusion: The concurrent use of fenugreek or garden cress alters theophylline pharmacokinetic behavior in an animal model. This could represent a modulation in cytochrome P450 activity, which is responsible for theophylline metabolism in beagle dogs. Further confirmation of these results in humans will warrant changes in theophylline dosing before the co-administration of such herbs.

Investigating the Potential Effect of Commiphora myrrha on the Pharmacokinetics of Theophylline, a Narrow Therapeutic Index Drug.

The present study was conducted to investigate the effect of commonly used herb Commiphora myrrha on the pharmacokinetic profile of theophylline (narrow therapeutic index drug) in rabbits. In the experimental groups, theophylline (16 mg/kg) was given orally to the rabbits. Where aqueous saline suspension of Commiphora myrrha (176 mg/kg, p.o.), was given to the rabbits and the blood samples were withdrawn at different time intervals (0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24 and 36 h) from marginal ear vein after dosing and theophylline in plasma was analyzed by HPLC method. It was observed that there a significant differences in the Cmax, AUC, AUMC, t1/2, and MRT of theophylline when coadministered with Commiphora myrrha which indicate that the herb affect the metabolism and elimination when coadministered with theophylline. Our results suggested that concurrent use of investigated herb alters the pharmacokinetics of theophylline. Confirmation of these results in human studies will warrant changes in theophylline dose or frequency when coadministered with herb under consideration.