Circadian variation in plasma theophylline concentrations during maintenance therapy with a sustained-release preparation in patients with obstructive airways disease

Plasma theophylline concentrations and airway function in asthmatic children receiving standard and modified RTC therapy

The effects of three different dosage schedules for sustained-release theophylline (Theolong) were investigated in children with asthma. With regimen II (unequal doses at 0800 h and 2000 h), the maximum plasma theophylline concentration following the evening dose was significantly higher than that following the morning dose, and also was larger than that following the evening dose with regimen I (equal doses at 0800 and 2000 h). With regimen III (equal doses at 0600 h and 2100 h), the mean theophylline concentration-time curve showed a single large peak at 1100 h, whereas with regimen I, there were two peaks at 2300 and at 1400 h. Knowledge that a change of the dosage schedule can affect the pharmacokinetics of theophylline in this way should aid physicians in its safe and effective use.

Bayesian derived predictions for twice daily theophylline under outpatient conditions and an assessment of optimal sampling times

1. The accuracy of a computerised method of pharmacokinetic interpretation of a single serum theophylline concentration, employing the statistical technique of Bayesian analysis, has been evaluated for an oral slow release form of theophylline using twice daily dosing. 2. Twenty-four hour steady state serum theophylline concentration-time profiles of one Uniphyllin Continus 400 mg tablet (Napp Laboratories) every 12 h were measured in 15 patients. These profiles demonstrated a diurnal variation of theophylline absorption which was faster during the day. 3. Revised predictions of the profiles were generated by Bayesian analysis using a single serum theophylline concentration taken during a previous outpatient appointment. Comparing the predicted and measured profiles, the accuracy of the Bayesian method is considered more than adequate for clinical purposes. 4. The predictions produced by the revised estimates were statistically less biased and more precise than those derived by a theophylline algorithm using population data. 5. The mean prediction errors of the revised estimates of the day and night-peak drug concentrations were -0.55 mg l-1 and -0.21 mg l-1 whilst those of the evening and morning troughs were 1.17 mg l-1 and 0.41 mg l-1, respectively. 6. Analysis of the predictive and relative performance of the samples drawn during the profile revealed that the sample taken prior to a morning dose produced the most accurate predictions. 7. There was no statistical difference in the relative predictive performance of samples drawn up to 4 h before or 2 h after the morning dose. It is, therefore, recommended that all serum theophylline concentrations to be used in Bayesian analysis, should be drawn within this period.

Improved control of asthma in the office setting. A large-scale study of once-daily evening doses of theophylline

A large-scale, multi-investigator open evaluation compared a once-daily regimen of controlled-release theophylline (Uniphyl tablets) with previous twice- or thrice-daily methylxanthine regimens. Three hundred asthmatic patients, 78 percent prone to nocturnal episodes during prior therapy, completed the investigation. Eighty-two percent of the patients were treated for moderate or severe disease. After a one-week evaluation of baseline theophylline therapy (with adjunctive medication), the patients substituted evening doses of the once-daily drug in approximate milligram-for-milligram equivalent doses. Concomitant medications were allowed as before. Nighttime and morning asthma control improved significantly without deterioration in the evening, and without increased side effects. Once-daily therapy resulted in markedly fewer night awakenings involving inhaler use (p less than 0.01), and near 60 percent reductions in the number of patients with nighttime or early morning exacerbations (p less than 0.01). Control of morning chest tightness, wheeze, and dyspnea improved significantly (p less than 0.01), and patients' as well as investigators' global evaluations favored once-daily treatment (p less than 0.01). Morning peak expiratory flow rates improved both at home (p less than 0.01) and at the office (p = 0.05). The forced expiratory volume in one second at the office increased modestly in the entire group. It is concluded that Uniphyl is effective and well tolerated when administered in once-daily evening doses.

A double-blind, placebo-controlled comparison of the efficacy of standard and individually titrated doses of theophylline in patients with chronic asthma

Forty adult patients with chronic asthma completed a 3-month double-blind crossover study to compare the effect of sustained-release theophylline given both as a fixed 300 mg twice daily dose (standard) and an individually titrated dose (titrated) with placebo. Theophylline was given in addition to other usual therapy, inhaled bronchodilators, inhaled steroids and, in 12 patients, oral steroids. The 3-month period was preceded by a run-in phase to determine the dose of theophylline which each subject required to achieve peak serum levels of 12-20 mg/litre and trough levels of 8-12 mg/litre. Doses ranged from 300 mg to 700 mg twice daily. Twenty-one patients needed more than the standard dose to achieve satisfactory serum levels. Patients recorded daily peak flow rates and symptom scores and were seen at monthly intervals to measure lung function, check serum theophylline levels and change treatments, which were given in random order. FEV1 was significantly higher for the whole group after standard (2.11 litres) and titrated (2.15 litres) theophylline therapy than after placebo (1.89 litres), as was FVC, but in the large subgroup whose titrated dose was greater than the standard dose, the FEV1 only improved with the titrated dose. Peak flow measurements at home showed the same pattern. Patients taking oral steroids appeared to derive less benefit from theophylline than others. It is concluded that theophylline can usefully be added as a third-line drug in chronic asthma, but that since half the patients are likely only to benefit from a dose greater than 300 mg twice daily, while the other half may have high serum levels above this dose, it is essential to measure serum levels in order to use the drug effectively and safely.

The pharmacokinetics and efficacy of slow-release theophylline with asymmetric dosing in asthmatic Chinese

Fifteen Chinese subjects with stable asthma were given asymmetric doses of slow-release choline theophyllinate (Theobret) according to body weight; patients under 60 kg (132 lb) received 180 mg at 9 AM and 360 mg at 9 PM for six days (period 1), followed by 180 mg at 1 PM and 360 mg at 9 PM for six days (period 2); for those over 60 kg, the regimen was the same, except that they received 270 mg during the daytime and 540 mg at night. At the end of each period of treatment, concentration of theophylline was measured over 24 hours. Five patients experienced side effects, and two of these were withdrawn from the study. In the remaining 13 patients, optimal concentrations of the drug were attained during most of the 24 hours, and there were only minor pharmacokinetic differences between the two periods of treatment. Compared with observations before treatment, the total symptom score was unchanged, but the peak expiratory flow rate in the morning and evening improved, and the use of inhaled bronchodilator drugs decreased significantly. There was a trend towards progressive improvement as the duration of treatment increased, suggesting that the therapeutic effect of theophylline may lag behind the attainment of optimal concentrations. We conclude that asymmetric dosing regimens of slow-release theophylline are effective and rational in maintenance therapy for asthma and that lower total daily dosages may be more appropriate in Chinese patients when compared to those recommended for white subjects.

Is diurnal variation in absorption of slow-release aminophylline an age-related phenomenon?

To specifically assess the possible influence of ageing on the changes in theophylline absorption, the plasma concentration-time profiles of sustained-release aminophylline were studied in 8 young and 8 elderly subjects after 9 a.m. and 9 p.m. administration. After 9 p.m. administration, in elderly subjects, maximum plasma theophylline concentrations (Cmax) were decreased, time to maximum concentration (tmax) was increased, and area under plasma concentration-time curve (AUC) was decreased compared to 9 a.m. dosing. This was true for single dose and at steady-state and suggests delayed and diminished absorption at night. No statistically significant changes were seen in the young subjects. This study therefore suggests that time related changes in absorption may be more significant in elderly subjects, possibly due to postural differences after 9 p.m. dosing, and this should be borne in mind when prescribing.

The effect of dosing time on the pharmacokinetics and pharmacodynamics of a 'once-a-day' sustained release theophylline preparation

1. The pharmacokinetics and the bronchodilating effect of theophylline were studied during 1 week of morning dosing and 1 week of evening dosing in a randomized cross-over design in thirteen patients with reversible airways obstruction, treated with a new 'once-a-day' theophylline capsule formulation. 2. There were no differences between the mean pre-dose trough plasma concentration, maximal plasma concentration, trough-to-peak variation, tmax, area under the plasma drug concentration time-curve after morning or evening dosage. There was only a slightly but significantly higher plasma theophylline concentration between 16 and 20 h after evening dosing. 3. The mean plasma drug concentration time-curves were relatively flat with a mean trough to peak variation of 73.9% after morning dosing and 66.7% after evening dosing. Both sets of mean data were within the 10-20 mg l-1 therapeutic range. 4. The variations in FEV1 and PEFR throughout the 24 h after either morning or evening dosing were similar and followed the normal pattern of diurnal variation. 5. Adverse effects were mild and occurred in three patients without causing discontinuation of the study. 6. The theophylline preparation used appears suitable for once a day administration either in the morning or in the evening.

Effects of time of dosing and age on intravenous aminophylline pharmacokinetics

The elimination kinetics of theophylline were investigated following intravenous administration of aminophylline in 12 subjects (six fit young, and six healthy hospitalised elderly volunteers) at 09.00 h and 21.00 h on separate occasions at least 5 days apart to determine whether time of administration had significant effects on clearance in young and elderly subjects. We were unable to demonstrate a significant change in kinetic parameters between morning and evening administration in either young or elderly subjects. Our results also demonstrated no difference in kinetics between young and elderly subjects. We conclude that neither time of dosing nor age are important determinants of theophylline elimination kinetics in healthy subjects.

Food induced changes in theophylline absorption from a once-a-day theophylline product

Bioavailability and the absorption pattern of theophylline from the sustained release theophylline (SRT) product, Uniphyllin, were studied in eight adults and eight children under fasting conditions in the morning, after a standardised breakfast in the morning, and under fasting conditions in the evening (adults only). Theophylline given intravenously was used as a reference. The extent of absorption of theophylline was complete for all administrations of SRT both in adults and children. In adults the absorption profiles after the three administrations of SRT were very similar and at no time point was there any difference in serum theophylline concentration or fraction absorbed between the three regimens. In addition, inter and intra individual variations in absorption were small. In children food caused a substantial change in the absorption pattern of theophylline so that the profiles became rather unpredictable with delays in absorption and periods of rapidly increasing serum drug concentrations. In three of the patients the dose dumping phenomenon resulted in toxic serum drug concentrations. Dumping of the dose could take place at any time interval between 3 and 15 h post dosing. Cmax was about 50% higher after fed than after fasting medication (P less than 0.01). It is concluded that children should not take SRT in large doses in combination with food.

Acute and chronic pharmacokinetics of asymmetrical doses of slow release choline theophyllinate in asthma

The day and night pharmacokinetics of assymetrical doses of slow release choline theophyllinate (Sabidal SR 270) were compared at day 1 and at day 4 of treatment when steady state had been achieved. Ten patients with chronic asthma were given oral choline theophyllinate 424 mg at 09.00 h and 848 mg at 21.00 h for 4 days. At regular intervals during day 1 and day 4 of treatment theophylline concentrations were measured in plasma and dried blood spots by fluorimmunoassay. Theophylline concentrations measured from dried blood spots were slightly lower than those in plasma, the difference remaining constant at all time points during day 1 and day 4 of treatment. On day 1 the mean peak plasma theophylline concentration was 5.4 +/- 1.0 (+/- s.e. mean) micrograms ml-1 4 h after the morning dose and 11.2 +/- 1.6 micrograms ml-1 4 h after the evening dose which were significantly (P less than 0.01) different. Similarly the areas under the plasma theophylline concentration-time curves at night were significantly (P less than 0.001) greater than those observed during the day. During day 4 mean peak plasma concentrations of theophylline after the morning and larger evening dose were 13.2 +/- 1.3 and 12.1 +/- 1.4 micrograms ml-1 respectively, which were not significantly different. No significant difference was observed between the areas under the plasma theophylline concentration-time curves during the day and at night. However the post-dose time to peak was significantly delayed at night (6 h) compared to the morning (2 h, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics of uniphyllin in nocturnal asthma

Three consecutive doses of approximately 10 mg/kg of a once daily slow-release theophylline preparation (Uniphyllin) were given at 22.00 hours to 15 patients with nocturnal asthma who were recovering from an acute exacerbation of their asthma. Twenty-four hour plasma theophylline profiles were obtained after the first and third doses. Following the first dose, the mean peak level was 12.5 mg/litre, mean time to peak was 8.1 hours and mean apparent elimination half-life was 6.6 hours. Pharmacokinetic data were similar following the third dose. In nocturnal asthma, Uniphyllin should be given at about 20.00 hours to coincide peak levels with the time of maximum airflow obstruction.

Timing of once-a-day theophylline dose to match peak blood level with diurnal variation in severity of asthma

To test the hypothesis that nighttime and early morning signs and symptoms of air flow obstruction in patients with moderately severe asthma would be better controlled by theophylline given on a once-a-day evening dosing schedule chosen to provide a peak blood level in the early morning than by the traditional twice-a-day dosing schedule designed to maintain levels more constant throughout the 24-hour period, the effects on nocturnal asthma of Uniphyl once a day and Theo-Dur twice a day were studied in 14 patients with moderately severe asthma. Although both regimens were effective, more patients preferred the Uniphyl dosing schedule. Nighttime symptoms were better controlled, without an increase in daytime symptoms or significant side effects. Optimal timing of theophylline dosing is an important consideration in the management of asthma.

Comparison of single and multiple dose pharmacokinetics of theophylline using stable isotopes

Theophylline, enriched with the stable isotopes 13C and 15N, was administered intravenously in a dose of 10 mg to 8 healthy men following single (200 mg) and multiple (200 mg 8-hourly for 5 days) oral dose administration of aminophylline. Total plasma clearance, volume of distribution, and half-time determined from the intravenous data were similar, demonstrating that the pharmacokinetics of theophylline after chronic dosing can be predicted from the pharmacokinetics of a single dose. With chronic oral dosing, however, the mean trough concentration was 12% higher at 9 a.m. than at 5 p.m., the end of the dose interval (3.94 +/- 0.55 vs. 3.50 +/- 0.45 micrograms X ml-1). The AUC following oral dosing was 25% higher in the multiple dose study than in the single dose study. Simulation analysis suggested that these results could be explained by diurnal variation in the clearance or absorption rate or a combination of both. Thus, the systemic availability of theophylline measured during a single dosage interval after chronic oral dosing to steady state would be overestimated in comparison with that measured after a single oral dose.

Circadian changes in the absorption and elimination of theophylline in patients with bronchial obstruction

Circadian variation in the serum concentration of theophylline has been reported in most patients receiving slow release oral preparations. To examine further the mechanism and clinical relevance of this change, an investigation has been made into the diurnal fluctuation in elimination kinetics during i.v. administration of theophylline and its serum concentration profile on oral treatment with a slow release preparation, in 8 hospitalized patients receiving it for bronchial obstruction. After reaching steady-state on a constant intravenous infusion, the total body clearance of theophylline (CL) was determined every 4-6 h from the steady-state concentration and the infusion rate. No systematic trend indicative of circadian changes in elimination kinetics was observed. The intraindividual fluctuation in CL during the observation period was small (coefficient of variation 4-11%). In contrast, on oral dosing a smaller area under the serum concentration-time curve was found during the night time (22.00-06.00). The results show that the circadian variation described in serum theophylline concentrations is due to delayed absorption at night. The elimination kinetics of theophylline do not change.

The rise and fall of serum theophylline concentration: a comparison of sustained-release formulations in volunteers with rapid theophylline clearance

The pharmacokinetics of four sustained-release formulations of theophylline have been examined after single doses (Nuelin SA, Phyllocontin, Slo-phyllin and Theo-Dur) and at steady-state (Phyllocontin, Theo-Dur) in six healthy adult volunteers, selected because they all eliminated theophylline rapidly after an intravenous dose of aminophylline. After a single dose of Theo-Dur, the peak concentration of theophylline was smaller and occurred later than after single doses of Nuelin SA, Phyllocontin and Slo-phyllin, suggesting that absorption occurs over a longer period. The systemic availability of theophylline was virtually complete after all four formulations. After repeated 12-hourly dosing to steady-state, and adjustment of dose to achieve trough concentrations of between 5 and 10 mg l-1 (28-55 mumol l-1), theophylline concentration fluctuated to a significantly greater extent within a dose interval when the subjects were taking Phyllocontin than when they were taking Theo-Dur.

Posture and theophylline kinetics

The effect of posture on theophylline kinetics was examined in six healthy men who took 450 mg slow-release aminophylline orally at the same time of day on two separate occasions. On one day they remained standing and on the other supine throughout. Plasma theophylline was measured hourly for 6 h from ingestion. Mean theophylline levels were significantly higher in the standing position at all times (P less than 0.01). We conclude that diurnal variation in theophylline kinetics can be explained, at least in part, by differences in posture.