The effect of 1-furan-2-yl-3-pyridine-2-yl-propenone on pharmacokinetic parameters of theophylline

The pharmacokinetic parameters of theophylline in rats did not change significantly when the drug was intravenously administered after three consecutive days of pretreatment with 17 mg/kg, orally, of 1-furan-2-yl-3-pyridine-2-yl-propenone (FPP-3), an investigatory drug having dual inhibitory action on cyclooxygenase (COX) and 5-lipoxygenase (5-LOX). However, significant changes were found in the pharmacokinetic parameters of the drug at doses of 34 mg/kg and more of FPP-3. Results of cytochrome P450 activity test indicated that the alteration in pharmacokinetic parameters of the drug appears to be due to the inhibitory effect of FPP-3 on cytochrome P450 1A which is responsible for the metabolism of theophylline. Methoxyresorufin-O-demethylase (MROD) and ethoxyresorufin-O-deethylase (EROD) activity assays revealed that the relative activities of cytochrome P450 1A1 and 1A2 were dose-dependently reduced in the presence of 1, 5, and 10 microM FPP-3 concentrations. Taking into consideration that FPP-3 is intended to be primarily used by geriatric patients with chronic diseases and therefore may be used in long-term basis, the investigatory drug needs to be assessed thoroughly in terms of drug interaction with other commonly prescribed medications.

Drug metabolizing enzyme CYP1A2 status in pediatric patients with hemoglobin E-beta thalassemia

OBJECTIVE

To evaluate the drug metabolizing enzyme CYP1A2 activity in pediatric hemoglobin E-beta-thalassemia patients, since CYP1A2 is responsible for the metabolism of a number of drugs. Alteration of its activity may have clinical consequences.

MATERIAL AND METHOD

Twenty-three hemoglobin E-beta thalassemia pediatric patients and 24 age-matched controls were recruited in the present study. Caffeine in the form of a soft drink was orally administered as a test probe for CYP1A2 activity. Plasma collected at pre-dose and 6 hr after intake was analyzed for the levels of caffeine and paraxanthine, its major metabolite to represent the activity of CYPIA2.

RESULTS

Biochemical markers, including blood glutathione and urinary lipid hydroperoxides indicated that patients were in an oxidant stress state. The plasma ratio of paraxanthine to caffeine was unchanged between patients and controls. Multiple regression analysis revealed that gender and the liver enzyme were the significant determinants of CYP1A2 activity (adjusted r2 = 0.48, p < 0.001). Male gender was associated with higher activity of CYP1A2 activity.

CONCLUSION

The CYP1A2 activity is not apparently changed in thalassemia patients despite the presence of an oxidative stress state.

On-line hemodialysis and hemoperfusion in a girl intoxicated by theophylline

In a suicidal attempt, a 15-year-old girl had ingested about 40 g of theophylline from sustained-release preparations. Symptoms of intoxication increased and serum concentrations of theophylline rose from 438 to 1,000 mumol/l. Conservative therapy was also combined by the use of hemodialysis as well as charcoal hemoperfusion on line. Treatment successfully reduced side-effects and S-theophylline within 12 hours and the patient could leave the hospital without residual sequelae. The combination of hemodialysis and hemoperfusion may reduce the risk of hypopotassiemia and hypocalcemia as well as increase in the clearance of the drug.

Chitosan and Sodium Sulfate as Excipients in the Preparation of Prolonged Release Theophylline Tablets

The major objectives of this study were to monitor the effect of cross-linking of cationic chitosan in acidic media with sulfate anion during granules preparation by wet granulation method prior to tableting using theophylline (TPH) as a model drug. The prepared granules and the compressed tablets were subjected to in vitro evaluation. The properties of the prepared matrix granules and the compressed tablets were dependent on chitosan:sodium sulfate weight ratios, chitosan content, and molecular weight of chitosan. The prepared granules of all batches showed excellent to passable flowability and were suitable for compression into tablets. Most of the granules were hard and expected to withstand handling during the subsequent compression into tablets. Granules with high friabilities were only those prepared with a high amount of sodium sulfate or low amount of chitosan. Compression of granule batches yield nondisintegrating tablets that showed a decrease in tensile strength with the increase of sodium sulfate content at high chitosan:sodium sulfate weight ratio or with decrease of chitosan content. On the other hand, friability of tablets was increased in the presence of an excessive amount of sodium sulfate and low chitosan content as observed with granules. Slow TPH release from the formulated tablets was achieved at 1:0.5 and 1:1 chitosan:sodium sulfate weight ratios where all or most of the cationic chitosan and sulfate anions were used in a cross-linking reaction during wet granulation. Ratios of 1:2 and 1:3 showed fast drug release, which support the hypothesis that excessive unreacted water-soluble sodium sulfate might increase the porosity of the nondesintegrating tablets during dissolution. Slow drug release was also obtained with high molecular weight chitosan, whereas changing the hardness of the tablets did not significantly change the release profile of the drug as long as the tablets are intact during dissolution. Furthermore, slow drug release was observed as the total amount of chitosan was increased in the formulated tablets. A comparative in vivo study between the chosen formulated tablets (1:1 chitosan:sodium sulfate ratio that contains 10% high molecular weight chitosan) and the commercial Quibron tablets indicated prolonged appearance of the drug in dogs' plasma for both formulations with no significant differences (p > 0.05) in rate and extent of drug absorption. The formulated tablets showed 103.16% bioavailability relative to that of the commercial tablets.

[Clinical review of patients with seizures that developed during theophylline administration--(III) Safety of theophylline examined in patients who had sequelae or died]

OBJECTIVE

To examine the causes of sequelae or death of patients who presented them subsequently to seizures that developed during theophylline administration.

METHODS

Among 334 patients who had been examined in Study (I), we extracted 56 who had sequelae or died subsequently to the onset of seizures and examined their causes.

RESULTS

Many patients had fever at the onset of seizures, many patients had neurologic predispositions prior to seizure onset, and only one patient was found to be free from fever and neurologic findings. At the onset of seizures, most of these patients had blood theophylline concentrations that were within or inferior to the target range (5-15 microg/mL).

CONCLUSIONS

We presume it necessary to pay heed to fever and neurologic predispositions in order to prevent sequelae or death that may occur subsequently to seizures that developed during theophylline administration.

Comparative bioavailability and in vitro in vivo correlation of two sustained release brands of theophylline: tablets and pellets

To investigate the influence of dosage forms on bioavailability, a randomized single-dose crossover study under fasting conditions was conducted using two commercially available sustained release products, Quibron SR tablets and Respro-SR pellets filled Capsules containing 300mg theophylline. A group of 12 healthy, male human subjects participated in this study. Serial blood samples were collected at 0, 1, 2, 3, 4, 6, 8, 10, 12 and 24 h. Theophylline was measured by high-performance liquid chromatography while absorption profiles were derived using Wagner-Nelson equation. The bioavailability of Quibron SR tablets was compared with Respro-SR pellets filled Capsules 300 mg using pharmacokinetic parameters Cmax, Tmax, AUC(0-t), and AUC(0-alpha). In addition, the 90% confidence interval (CI) for the ratio of logarithmic transformed C(max) and AUC(0-alpha) was also used to determine bioequivalence. The T/R (test/reference) ratio of Quibron SR tablets was quite close to the prescribed limits of bioequivalence i.e. 80-125%. No statistically difference was observed between the log transformed AUC(0-agr;) (P=0.971) values as well as log transformed C(max) values (P=0.854) indicating bio-availability and the extent of absorption of two brands were comparable. Moreover, the value of correlation coefficients for % in vivo absorption versus % in vitro dissolution of the two products was calculated to be 0.9533 for Respro-SR capsule and 0.9789 for Quibron-SR tablets.

Severe metabolic complications from theophylline intoxication

Theophylline is commonly used in the treatment of bronchospastic lung disease. In addition to gastrointestinal and cardiac dysfunction, hypokalaemia, lactic and ketoacidosis can complicate theophylline overdose. Clinicians frequently fail to identify theophylline's role when complications develop. A case of an 80-year-old man who developed profound metabolic disturbances while hospitalized is presented. The typical causes of these abnormalities were absent, theophylline levels were elevated, and the patient recovered after theophylline was held. Based on our case and review of the literature, we discuss the reasons why theophylline toxicity is under-recognized, and propose mechanisms for the rare metabolic abnormalities identified in this case. A high index of suspicion for theophylline toxicity should be maintained and it should be considered when unexplained acidosis or hypokalaemia occur.

Perinatal dioxin exposure, cytochrome P-450 activity, liver functions and thyroid hormones at follow-up after 7-12 years

OBJECTIVES

Prenatal and lactational exposure to Dutch "background" dioxin levels may cause health effects spanning many years. In addition, perinatal studies have shown a relationship between dioxin exposure and thyroid disturbance. To assess the later health effects of prenatal and lactational dioxin exposure on liver function we measured plasma ALAT and ASAT levels amongst our longitudinal cohort, as was done perinatally and at 2(1/2) years. The children underwent a caffeine loading test to determine CYP1A2 activity. To assess the later effects on thyroid function we measured plasma TSH and FT4.

STUDY DESIGN

A longitudinal cohort of 37 healthy children (age 7-12, mean 8.2 years), with documented prenatal and lactational dioxin exposure, ingested 3mg caffeine/kg BW 6h prior to blood withdrawal. Paraxanthine/caffeine molar ratio, ALAT, ASAT, TSH and FT4 were determined in venous blood.

RESULTS

Linear regression of ASAT and ALAT revealed no relation with prenatal and lactational dioxin exposure. No correlation was found between the paraxanthine/caffeine molar ratio and prenatal and lactational dioxin exposure. Linear regression of TSH and FT4 revealed no relation with prenatal and lactational dioxin exposure.

CONCLUSION

This follow-up has shown a normalisation of previously abnormal ALAT and ASAT levels, indicating a transient effect. CYP1A2 activity, measured by means of a caffeine-loading test, revealed no correlation with the prenatal and lactational exposures. A normalisation of previously abnormal thyroid hormone homeostasis was seen, also possibly indicating a transient effect. This study provides new data on long-term follow-up after perinatal dioxin exposure to background levels of dioxins.

In-vitro/in-vivo correlation of pulsatile drug release from press-coated tablet formulations: A pharmacoscintigraphic study in the beagle dog

The aim of the current study was to investigate the in-vitro and in-vivo performance of a press-coated tablet (PCT) intended for time delayed drug release, consisting of a rapidly disintegrating theophylline core tablet, press-coated with barrier granules containing glyceryl behenate (GB) and low-substituted hydroxypropylcellulose (L-HPC). The PCTs showed pulsatile release with a lag time dependent upon the GB and L-HPC composition of the barrier layer. In-vivo gamma-scintigraphic studies were carried out for PCTs containing GB:L-HPC at 65:35 w/w and 75:25 w/w in the barrier layer in four beagle dogs, in either the fed or fasted state. The in-vivo lag time in both the fed and fasted states did not differ significantly (p>0.05) from the in-vitro lag time. Additionally, no significant difference (p<0.05) between in-vivo fed and fasted disintegration times was observed, demonstrating that in-vivo performance of the PCT was not influenced by the presence or absence of food in the gastrointestinal tract. A distinct lag time was obtained prior to the appearance of drug in plasma and correlated (R2=0.98) with disintegration time observed from scintigraphic images. However, following disintegration, no difference in pharmacokinetic parameters (AUC(0-6 dis), K(el), Cmax) was observed. The current study highlighted the potential use of these formulations for chronopharmaceutical drug delivery.

Pharmacokinetics of an extended-release theophylline product in cats

OBJECTIVE

To evaluate the pharmacokinetics of a brand of extended-release theophylline tablets and capsules in healthy cats.

DESIGN

Randomized 3-way crossover study.

ANIMALS

6 healthy cats.

PROCEDURES

A single dose of aminophylline (10 mg/kg [4.5 mg/lb], IV), a 100-mg extended-release theophylline tablet, or a 125-mg extended-release theophylline capsule was administered to all cats. Plasma samples were collected via preplaced central catheters throughout a 36-hour period. Plasma samples were frozen until analyzed by use of a fluorescence polarization monoclonal immunoassay.

RESULTS

All cats tolerated drug administration and plasma collection with no adverse effects. Peak concentrations were reached for both orally administered products between 8 and 12 hours after administration. Bioavailability was excellent. Plasma concentrations were within the human therapeutic concentration of 5 to 20 microg/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Daily administration of the brand of theophylline tablets and capsules used in this study at 15 mg/kg (6.8 mg/lb) and 19 mg/kg (8.6 mg/lb), respectively, maintained plasma concentrations within the desired therapeutic range in healthy cats.

In vitro and in vivo sustained-release characteristics of theophylline matrix tablets and novel cluster tablets

We compared the in vitro/in vivo properties of theophylline between two sustained-release preparations, which are administered once a day. Tablet A is a swelling/disintegration-type matrix tablet consisting of hydrophobic wax granules and hydrophilic polymer granules (cluster tablets). Tablet B is a matrix tablet consisting of hydrophilic polymer granules. We conducted a dissolution test with JPXIV in vitro, and compared the results between the two preparations. Neither pH nor agitation intensity influenced these preparations. After they were immersed in oleic acid, there were no marked changes in the dissolution properties in the dissolution test. After administration of Tablets A and B containing theophylline at 200mg to fasted dogs, we compared plasma level profiles of theophylline. The mean plasma level of theophylline gradually increased to a maximum (7.17microg/mL) 4h after administration of Tablet A. After administration of Tablet B, a similar finding was noted, with a maximum of 6.09microg/mL. Tablet B showed a higher coefficient of variation (CV) for the plasma level at each point. Subsequently, we administered two tablets of preparations A and B containing theophylline at 200mg to healthy volunteers who had not been fasted, and compared plasma level concentration of theophylline. The mean plasma level of theophylline gradually increased to a maximum (6.09microg/mL) 12h after administration of Tablet A, but then decreased, with a half-life of 9.10h. After administration of Tablet B, a similar finding was noted, with a maximum of 7.87microg/mL and a half-life of 7.76h. Tablet A showed a significantly higher plasma concentration 1 and 2h after administration; however, there were no significant differences at other points. The C(max) of Tablet B was significantly higher than that of Tablet A. However, there were no significant differences in other pharmacokinetic parameters between the two preparations. The T(max) of Tablet A was 10-12h after administration, relatively constant. However, that of Tablet B was 10-18h after administration. The CV for T(max) was 9.8% for Tablet A and 22.0% for Tablet B. After administration of Tablet B, the plasma level of theophylline varied at each point. Based on these results, inter-subject variations after administration of Tablet A may be less marked than those after administration of Tablet B. It is concluded that, the cluster tablets A developed in this study showed significantly less inter-subject variation of theophylline plasma levels than the conventional matrix tablets B.

[A clinical review of patients with convulsions during theophylline administration II: points to consider in administration and prognosis as determined in patients with theophyline toxicosis]

OBJECTIVES

To discover features of patients with theophylline toxicosis among patients who developed convulsions during theophylline administration.

METHODS

Fifteen patients, whose measured or estimated blood theophylline concentration at the time of convulsion development was >/=40 microg/mL, were extracted out of 334 patients who were reported between October 1987 and April 2004 and who developed convulsions during theophylline administration (oral theophylline: 255 patients; intravenous theophylline: 79 patients). Patient background, state of drug administration, blood theophylline concentration, presence or absence of status epilepticus, and outcome were examined.

RESULTS

Young children and children with fever were predominant, and eight of 15 patients had both features. Furthermore, the dose exceeded the currently recommended target dose in most of patients whose given dose is known. Patients with misdispensing and patients having problems with administration and ingestion methods were included in them. Outcomes included one case of death, two cases of sequelae, 11 cases of recovery or alleviation, and 1 case of unknown. The patient who died took large doses of theophylline, and both of two patients who had sequelae had fever associated with an infection.

CONCLUSIONS

Our study revealed 1) heed should be given to the age of the affected child and to theophylline administration when fever is present in order to avoid theophylline toxicosis and 2) many patients with the toxicosis (11/15) present a relatively favorable prognosis.

Herb-drug interactions: Effect of Ginkgo biloba extract on the pharmacokinetics of theophylline in rats

Herbal medicines have received great attention as alternative medicines in recent years and are also referred to as a dietary supplement or health food. Ginkgo biloba extract (GBE) is one of the most popular herbal medicines. However, little is known about the metabolic interactions between GBE and clinically used drugs. This study attempted to investigate the effect of GBE on the pharmacokinetics of theophylline, a cytochrome P450 (CYP) 1A2 substrate and an important therapeutic agent with narrow therapeutic window used for the treatment of asthma. Commercial GBE (10 or 100 mg/kg, p.o.) or water (control group) was given to rats (6 rats for each group) for 5 consecutive days and on the sixth day theophylline (10 mg/kg) was administered either orally or intravenously. The results showed that pretreatment of rats with GBE resulted in an increase in the total clearance of theophylline of about 30% (GBE 10 mg/kg, P<0.05) and 70% (GBE 100 mg/kg, P<0.01) compared with the control group after intravenous administration of theophylline (10 mg/kg). After oral administration of theophylline (10 mg/kg), the AUC(0-24h) of theophylline was reduced by 40% following pretreatment with GBE (100 mg/kg, P<0.01). These results demonstrate that GBE pretreatment increased CYP1A2 metabolic activity and the clearance of theophylline in rats.

Weighted target interval stochastic control methods with global optimization and their applications in individualizing therapy

Several improvements on the target interval stochastic control (TISC) method are addressed for individualizing therapy. In particular, a global optimization control strategy is implemented to obtain the optimal dosage regimen, and weighting functions are introduced to balance the drug efficacy and the risk of toxicity. Since general guidance is often lacking in the determination of a weighting function, we introduce a systematic approach, i.e., the standard reference gamble method of medical decision theory, for the determination of the weighting function. The population model for the individualization of theophylline therapy reported by D'Argenio and Katz is applied in this research. The present method of the integration of weighting functions and global optimal strategy offer an effective and safe means to balance the drug efficacy and risk of toxicity. In addition, it also achieves better accuracy than the existing TISC method which uses a local optimal strategy.

Appropriate phenotyping procedures for drug metabolizing enzymes and transporters in humans and their simultaneous use in the "cocktail" approach

Phenotyping for drug metabolizing enzymes and transporters is used to assess quantitatively the effect of an intervention (e.g., drug therapy, diet) or a condition (e.g., genetic polymorphism, disease) on their activity. Appropriate selection of test drug and metric is essential to obtain results applicable for other substrates of the respective enzyme/transporter. The following phenotyping metrics are recommended based on the level of validation and on practicability: CYP1A2, paraxanthine/caffeine in plasma 6 h after 150 mg caffeine; CYP2C9, tolbutamide plasma concentration 24 h after 125 mg tolbutamide; CYP2C19, urinary excretion of 4'-OH-mephenytoin 0-12 h after 50 mg mephenytoin; CYP2D6, urinary molar ratio debrisoquine/4-OH-debrisoquine 0-8 h after 10 mg debrisoquine; and CYP3A4, plasma clearance of midazolam after 2 mg midazolam (all drugs given orally).

A simple and rapid HPLC/UV method for the simultaneous quantification of theophylline and etofylline in human plasma

A simple, sensitive and selective high performance liquid chromatography (HPLC) method with ultraviolet detection (272 nm) was developed and validated for the simultaneous quantification of theophylline and etofylline in human plasma. Following rapid sample preparation, the analytes and internal standard (hydrochlorothiazide) were separated using an isocratic mobile phase on a reverse phase C18 column. The lower limit of quantification was 100 ng/mL for both theophylline and etofylline with a relative standard deviation of less than 6%. A linear dynamic range of 100-10,000 ng/mL for both theophylline and etofylline was established. This HPLC method was validated with between-batch precision of 2.2-6.0 and 1.4-3.7% for theophylline and etofylline, respectively. The between-batch accuracy was 94.3-98.0 and 95.4-98.2%, respectively. Stability of theophylline and etofylline in plasma was excellent, with no evidence of degradation during sample processing (autosampler) and 30 days storage in a freezer. This validated method is simple and rugged enough to be used in pharmacokinetic studies.

First-line therapy for theophylline-associated seizures

Theophylline-associated seizures (TAS) are considered a neurologic emergency, as they can sometimes be intractable and difficult to stop with standard treatments such as intravenous administration of diazepam. As a consequence, a proportion of patients who experience status epilepticus while receiving theophylline will require endotracheal intubation. The optimal first-line therapy for TAS has not yet been fully investigated. We compared 54 cases of TAS with 779 cases of non-TAS, that had presented at a single institution between 1991 and 2002. Among the 54 cases of TAS, 36 experienced generalized tonic-clonic seizures, with the remainder experiencing partial seizures. TAS occurred mainly in children under 3 years of age, and serum theophylline levels were within the therapeutic range in 78% of the cases. The duration of TAS tended to be longer than for non-TAS, and intravenous administration of diazepam was less effective in controlling TAS (45%), compared with non-TAS (68%). Many cases required repeated injections of diazepam, and 15 cases (27%) eventually required endotracheal intubation. Reports concerning the therapy for TAS were also reviewed. Theophylline is known to antagonize the effects of benzodiazepines, and this may explain why drugs such as diazepam are relatively ineffective in treating TAS. In TAS, the prompt use of barbiturates is recommended when diazepam is not effective, to avoid potential brain injury secondary to status epilepticus.

Theophylline granule formulation prepared by the wet granulation method: comparison of in vitro dissolution profiles and estimation of in vivo plasma concentrations

The primary and secondary objectives of this study were to develop and evaluate the predictability of in vitro-in vivo correlation models for theophylline sustained release (SR) granules. Theophylline SR granules meeting the USP Drug Release Test criteria were prepared using ethyl cellulose (EC) and/or stearyl alcohol (SA) and the wet granulation method. In vitro dissolution studies of granule formulation were performed, and a commercial dosage form was prepared using USP XXIII apparatus II at pH 4.5. Differences and similarities between in vitro dissolution curves were compared using both model-dependent (t-test) and -independent (f1, f2 test) statistical techniques, and it was shown that the three dissolution profiles i.e model-dependent, model-independent, and methods based on ANOVA were very similar. The in vivo performance of the commercial dosage form was tested by oral route using male rabbits and in vitro-in vivo correlations were established. This study indicates that the dosage forms with similar in vitro dissolution profiles may have a similar in vivo performance, and that this performance could be estimated using appropriate correlation equations.

Frequent toxicity from IV aminophylline infusions in critically ill patients. 1977

Use of recommended IV aminophylline dosage regimens in 48 older, acutely ill, hospitalized patients with chronic obstructive pulmonary disease (COPD) resulted in excessive plasma theophylline concentrations in 29 percent of these patients.

A mean dose of 0.89 mg/kg/hr produced a plasma concentration which ranged from 7 to 52 mcg/ml with a mean of 21.9 mcg/ml. Plasma theophylline concentration was determined spectrophotometrically from plasma samples drawn at least 12 hours after a loading dose and initiation of a constant infusion. Severity of toxicity strongly correlated with the plasma theophylline concentration in 18 patients. Nausea and/or vomiting preceded life-threatening drug-induced arrhythmias and seizures less than half the time. Tachycardia was found to be the most consistent symptom associated with toxicity. These patients had lower plasma clearances than otherwise healthy younger adult asthmatics and healthy volunteers. Toxicity and identifiable risk factors for excessive plasma levels strongly correlated with reduced plasma clearance. Dosage modifications based upon plasma clearances from COPD patients without concurrent functional abnormalities and those with liver dysfunction and cardiac decompensation ranged from 0.7 to 0.12 mg/kg/hr. This study clearly demonstrates the poor correlation between dose and plasma concentration and the strong relationship between toxicity and plasma concentration. These results as well as those previously reported mandate that the relatively simple, rapid and inexpensive theophylline plasma measurement be used in all patients receiving IV aminophylline for longer than 24 hours in order to prevent toxicity.

Awareness and use of caffeine by athletes competing at the 2005 Ironman Triathlon World Championships

This study assessed the knowledge, prevalence, and quantity of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Caffeine-related questionnaires were self-administered to 140 (105 male and 35 female, 40.3 +/- 10.7 y) athletes representing 16 countries. Fifty of these athletes further consented to immediate post-race blood samples for analysis of plasma caffeine and paraxanthine using high-performance liquid chromatography (HPLC). Seventy-two percent of 70 athletes correctly identified caffeine as being an unrestricted substance in triathlon. The majority of athletes [125 (89%)] were planning on using a caffeinated substance immediately prior to or throughout the race. Cola drinks (78%), caffeinated gels (42%), coffee (usually pre-race) (37%), energy drinks (13%), and NoDoz tablets (9%) were the most popular caffeinated choices. Mean +/- standard deviation (and range) post race plasma caffeine and paraxanthine levels were 22.3 +/- 20 micromol/L (1.7 to 98.4) and 9.4 +/- 6 micromol/L (1.8 to 28.9), respectively. Seven athletes (14%) finished with plasma caffeine levels > or = 40 micromol/L. Plasma values from elite athletes did not differ from age group competitors. Despite the prevalence of its consumption and the training experience of this athletic group, over one quarter of athletes remained either confused or uninformed about caffeine's legality. Levels of plasma caffeine taken immediately post race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e., approximately 20 micromol/L or a dose of > or = 3 mg/kg body weight).

Acetic acid improves the sensitivity of theophylline analysis by gas chromatography–mass spectrometry

In the analysis of theophylline by gas chromatography-mass spectrometry (GC-MS), we found that the addition of acetic acid to the solvent (ethyl acetate) decreased the adsorption of theophylline to the glass wool packed into the inlet liner. The addition of acetic acid to ethyl acetate improved the sensitivity for theophylline (optimum concentration of 3%). This simple and sensitive method without derivatization can be applied to the quantification of theophylline in serum samples in clinical and toxicological practice.

Pharmacokinetics of Theophylline in Guinea Pig Tears

It is well recognized that the theophylline (TP) concentration in human tears correlates well with the free TP concentration in human plasma. However this correlation was found only in a very narrow range of concentrations of TP, and pharmacokinetic analysis of TP in tears has not been carried out for a wide range of concentrations of TP. The aims of this investigation were to develop a simple kinetic model for TP in guinea pig plasma (total [Cf+b] and free [Cf]), cerebrospinal fluid (CSF) [C](CSF) and tears [C](T), and to examine whether [Cf], [Cf+b] and [C](CSF) can be predicted from [C](T) using the resulting kinetic parameters. [Cf+b], [Cf], [C](CSF) and [C](T) were determined by GC/EI-SIM following bolus i.v. injection of TP in doses of 10, 50 and 100 mg/kg into guinea pigs. The wide range of concentrations of [Cf+b] could be quantitatively described by a two-compartment model with non-linear elimination kinetics and individual volume distribution of TP at each dose. [C](T) and [C](CSF) were analyzed using passive diffusion models with and without the pH-partition theory, respectively. The value of [Cf] could be predicted from the value of [C](T). Thus, the measurement of [C](T) which can be collected non-invasively would be a useful method for the therapeutic drug monitoring of TP.

[Drug therapy of asthma. Results of the 1998 German National Health Interview and Examination Survey]

The lifetime prevalence of bronchial asthma in adults is approximately 5%. Recommended drug therapy of this condition depends largely on its severity and varies from the on demand use of bronchodilators as a single measure up to the additional and sometimes permanent use of inhaled and/or systemic glucocorticoids. In this study, the prevalence and drug therapy of bronchial asthma were analysed in a representative sample of the resident population in Germany aged 18-79 years. We also report about health care utilization, like hospital stay, emergency treatments and use of ambulant medical care, and its associations with asthma medication. Of those study participants who affirmed a medical diagnosis of asthma, 17.3% used corticoid drugs continuously, 19.1% occasionally and 61.8% never. Use of medical services after an asthma attack was reported most often by those who took corticoid drugs regularly. Older people with asthma mostly used glucocorticoids regularly, while in very young patients the occasional use of corticoids was reported more often. When looking at the actual drug use (7 days before the examination) according to the drug usage questionnaire, anti-asthma drugs were mentioned as follows: 47.8% of persons with asthma, diagnosed during the last 4 weeks, used inhaled adrenergic drugs, 34.8% inhaled glucocorticoids, 2.1% systemic adrenergic drugs and 19.3% systemic theophyllines. The measured serum concentrations of theophylline were below 5 mg/l in 34.4%, between 5 and 8 mg/l in 28.1%, between 8 and 20 mg/l in 35.9% and somewhat over 20 mg/l in 1.6%. Our data suggest that especially young asthmatics may not be sufficiently treated with anti-inflammatory therapy, but further studies are needed. If such a deficit can be confirmed, measures for better adherence of therapy to existing guidelines should be considered. Our results, especially on serum concentrations of theophylline, suggest that therapeutic drug monitoring (TDM) of serum samples is not only an important tool in health surveys, but also suitable for increasing the safety and quality of drug treatment in asthmatics.

[Clinical review on patients who developed seizures during theophylline administration: relationships with seizure-predisposing factors]

OBJECTIVE

In recent years, attempts have been made to broadly deem seizures developing during theophylline administration as theophylline-related seizures. Consequently, a tendency to consider all the seizures attributable to theophylline has occurred. We investigated background factors in pediatric patients with seizures to examine the involvement of theophylline in the event.

METHODS

Of adverse events developing during theophylline administration which were reported by two theophylline preparation manufacturers between October 1987 and April 2004, we investigated underlying disease, regimen, outcome, and other items in 255 patients with seizures provoked by oral preparations and in 79 patients with seizures provoked by intravenous preparations.

RESULTS

The most predominant factors were represented by neurological predispositions, e.g., epilepsy, and by a history of fits prior to the onset of seizures in not less than two-thirds of pediatric patients with seizures who were receiving theophylline. Furthermore, not less than 90% of pediatric patients who remained with sequelae and who died had the factors. Our investigation revealed that the factors developed predominantly when the relevant patients presented fever, aged under 3 years and had history of seizures.

CONCLUSIONS

Therefore, we consider that advertence to this point is most important in administering theophylline safely.