Single-dose slow-release aminophylline at night prevents nocturnal asthma

Controlled release salbutamol tablets versus sustained release theophylline tablets in the control of reversible obstructive airways disease

A crossover pilot study was undertaken to compare the acceptability of controlled release salbutamol tablets (8 mg twice daily) with a sustained release theophylline preparation (400-800 mg given once each night) in patients with reversible obstructive airways disease. A 2-week run-in period was used to titrate the theophylline dosage. Patients were then allocated at random to one of the treatments before being immediately crossed over to the other for a further 4 weeks. Thirty-two patients, aged 17-66 years, entered the trial. Seventeen patients (53%) were withdrawn. The majority of the 13 withdrawals due to side-effects of theophylline occurred during the run-in period. There were no statistically significant differences between treatments for either lung function tests performed at the clinic or for peak expiratory flow rate recorded by the patients. The non-asthma symptom score was significantly higher with theophylline than with the salbutamol preparation. A preference for treatment with the controlled release salbutamol tablets was expressed by 11/15 patients.

How much theophylline is enough?

Theophylline not only is a bronchodilator but also has other effects (inhibition of mediator release, enhancement of mucociliary clearance, enhancement of diaphragmatic contractility) that are potentially beneficial to asthmatic patients. Recent studies suggest that theophylline pharmacodynamics vary among asthmatic patients. However, on average, most of the total bronchodilatory response occurs at serum theophylline concentrations of 0 to 10 mg/liter. Additional (but less) bronchodilatation occurs at serum theophylline levels between 10 and 20 mg/liter. Pharmacodynamic relationships are not well established for other therapeutic effects of theophylline, such as attenuation of pharmacologically induced bronchoconstriction. An important feature of oral controlled-release theophylline therapy is timing of drug administration. Because airway reactivity increases and airway caliber decreases at night, it has been suggested that the greatest benefit is derived from theophylline when peak serum concentration is reached during the night or the early morning.

Inflammatory mechanisms and nocturnal asthma

The results of recent research strongly suggest that airway inflammation, which may increase at night as a result of circadian troughs in blood epinephrine and cortisol concentrations, underlies the bronchial hyperresponsiveness that is almost certainly a major contributor to the pathogenesis of nocturnal asthma. This article reviews what is known about the nature and complex interactions of the inflammatory cells and mediators that may be involved in asthma, with particular emphasis on nocturnal asthma. The roles of platelet-activating factor antagonists, corticosteroids, and theophylline in suppressing this response also are discussed.

Terbutaline sustained-release tablets in nocturnal asthma--a placebo-controlled comparison between a high and a low evening dose

The effects of oral treatment with terbutaline sustained-release (SR) tablets (Bricanyl Depot) were studied in nine patients who had bronchial asthma and marked diurnal variation in ventilatory function. In a randomized and double-blind study, the patients were treated with terbutaline SR 7.5 mg b.i.d., terbutaline SR 7.5 mg in the morning and 15 mg in the evening and terbutaline SR placebo b.i.d. Each treatment was given for 1 week. The nocturnal decline in the peak expiratory flow rate (PEFR) was 45% during the placebo period, 27% after the lower and 22% after the higher terbutaline SR evening dose (P less than 0.01 for both treatments compared to placebo). The mean morning PEFR was significantly higher with the high evening dose than with the low evening dose (P less than 0.01). Mild to moderate side effects were noted. The sustained-release preparation of terbutaline seems to be of clinical value in preventing or relieving nocturnal asthma and early morning dipping. The flexible dose technique, with a higher evening dose, results in further improvements in these patients.

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.

The utility of a long-acting sympathomimetic agent, procaterol, for nocturnal asthma

Patients with nocturnal asthma have their lowest pulmonary function and lowest serum epinephrine level at 4 to 6 AM. We studied a new long-acting beta-adrenergic agonist, procaterol, in ten patients with nocturnal asthma. The patients received 0.1 mg of procaterol one night and a placebo the other night in random order. Pulmonary function tests were performed every two hours from 10 PM to 8 AM. Pulmonary sounds were recorded using a modified stethoscope and were subsequently analyzed to estimate the proportion of time occupied by wheezing (est Tw/Ttot). The forced expiratory volume in one second (FEV1) while receiving the placebo and procaterol were similar at 10 PM (placebo, 1.35 +/- 0.18 L [mean +/- SE]; procaterol, 1.48 +/- 0.20 L); however, by 4 AM, the FEV1 had dropped significantly lower on the night with the placebo (1.01 +/- 0.14 L) than the night with procaterol (1.30 +/- 0.19 L; p less than 0.05). The est Tw/Ttot was similar at 12 AM for both nights, but at 4 AM, there was a significant increase in the est Tw/Ttot for the group with placebo but not the group with procaterol. The use of a long-acting beta-adrenergic sympathomimetic agent reversed the obstruction of the airways seen with nocturnal asthma.

Xanthines--symptomatic or prophylactic in asthma?

Perhaps xanthines should not be classified as bronchodilators because their clinical efficacy may reflect their antiinflammatory properties more than smooth muscle relaxation. Xanthines inhibit late phase airway reactions induced by allergen or chemical sensitizers. But, they offer little protection against methacholine-, histamine, or allergen-induced immediate bronchoconstriction and any protection seen is unrelated to the extent of the initial bronchodilatation. The antiinflammatory effects of xanthines include stabilization of a variety of inflammatory cells that are present in asthmatic airways. Another potentially important effect is the increase in number, and activity, of "suppressor" T-lymphocytes. Xanthines may also stabilize the barrier functions of both the airway epithelium and the airway microvessel (venular) wall. As a result less cellular and plasma-derived mediators are released, less plasma is exuded into the airway wall and less plasma enters the airway lumen. Penetration of inhaled macromolecules across the epithelium and into the airway wall may also be reduced. Future prospects for xanthines are interesting. A novel xanthine which lacks adenosine antagonist activity, enprofylline, has been shown to exert potent antiasthma actions without producing several of the excitatory, extrapulmonary, theophylline-like effects. We are only now starting to learn how xanthines actually work in the inflamed asthmatic and bronchitic airway. Nevertheless, the currently available data show that xanthines are likely to be more prophylactic than symptomatic in the treatment of asthma and chronic obstructive airway disease.

The drug therapy of asthma: directions for the 21st century

There are several novel pharmacological approaches to asthma therapy which have resulted from a further understanding of airway smooth muscle function and inflammatory mechanisms involved in asthma. The most effective bronchodilators currently available are beta 2-adrenoceptor agonists and drugs with a prolonged duration of action after inhalation will be useful. Other possible bronchodilator approaches include vasoactive intestinal peptide, prostaglandins, novel xanthines, selective muscarinic antagonists, drugs interfering with intracellular calcium release and K+-channel activators. The most effective anti-inflammatory treatment is corticosteroids and efforts are being made to improve the topical potency of these drugs. Many other ways of reducing inflammatory effects in asthma are being explored, such as mediator antagonists (especially thromboxane and PAF antagonists), inhibitors of inflammatory cell activation (especially of eosinophils) and inhibition of neurogenic inflammation. Use of anti-inflammatory therapies earlier in the disease should become more widespread.

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.

The accuracy of a pharmacokinetic theophylline predictor using once daily dosing

1. The accuracy of a computer based pharmacokinetic prediction method based on Bayesian analysis has been evaluated for an oral show release form of theophylline. 2. In 83 patients from seven centres 24 h serum theophylline concentration-time profiles were measured under a variety of circumstances. 3. Revised predictions of 24 h serum theophylline concentration profiles were generated by Bayesian analysis using single serum drug concentrations taken before, during and after the study days in different subgroups of those patients. Comparing the predicted and measured profiles the mean prediction error (bias) was 0.05 mg l-1 for peak concentrations and 0.04 mg l-1 for trough concentrations during once daily dosing. The corresponding root mean squared prediction errors (precision) were 2.59 and 1.17 mg l-1, respectively. 4. This accuracy is considered more than adequate for clinical purposes. 5. The technique can be used with a variety of other drugs and can form a valuable part of a routine therapeutic drug monitoring service.

Is there a circadian variation in respiratory morbidity?

In a retrospective study of the time of presentation to an accident and emergency department patients with acute respiratory symptoms presented more commonly at night compared to a control group with abdominal pain. In a subsequent prospective study doctors from a GP deputizing service were called much more frequently at night by patients with asthma than by those with other symptoms. These findings refute the suggestion that the observed increased mortality from respiratory diseases at night results from reduced medical care as a consequence of a reluctance of patients to present during the night.

Diurnal rhythm of asthma

A diurnal rhythm in the occurrence and severity of asthma symptoms is almost universal with disturbed sleep due to enhanced symptoms at night paralleled by a change in lung function. The mechanisms involved are not completely understood. However, it appears to be related to an exaggerated response to a circadian rhythm in lung function observed in healthy individuals. The circadian nature of asthma must be considered in diagnosis and evaluating the adequacy of therapy. Inhaled therapy with additional suppressive and anti-inflammatory treatment as required should be effective in treating most patients with nocturnal asthma.

Unequal twice-daily, sustained-release theophylline dosing in chronic obstructive pulmonary disease

Three regimens of sustained-release theophylline (SRT), Theostat were administered to 12 male patients with chronic obstructive pulmonary disease in a randomized cross-over trial. Each 7-day treatment consisted of: treatment A--8 mg/kg at 0700 hr and 4 mg/kg at 1900 hr, treatment B--6 mg/kg at 0700 hr and 6 mg/kg at 1900 hr, treatment C--4 mg/kg at 0700 hr and 8 mg/kg at 1900 hr. Peak expiratory flow (PEF) was recorded each day at 0700, 1100, 1500, 1900 and 2300 hr and theophylline plasma levels were determined on the 7th day of each treatment sequence. Cosinor analysis of the data revealed significant circadian rhythms in PEF for each treatment: the mesor (24-hr average) was significantly higher with C and acrophases (phi, peak time of PEF rhythm) were located at 1426 hr for A and 1425 hr for C; a shift of the acrophase to an earlier timing was detected for B (phi = 0958 hr. These findings suggest that an unequal, twice-daily SRT dosing with the greater amount of drug at night may be beneficial in the treatment of COPD.

Comparison of sustained-release theophylline scheduled conventionally (twice-daily, equal interval in equal amount) versus once-daily mornings or evenings on circadian pattern of bronchial patency in asthmatics

The effects of differently timed, but equivalent TheoDur (Key Pharmaceutical Co.) dosage schedules--twice-daily equally divided 12 hr (BID), once-daily evening (OD-PM) and once-daily morning (OD-AM)--were compared under steady-state conditions in 10 adult asthmatics with a documented history of nocturnal dyspnea. Assessments of airways function by spirometry were done every 3-hr over one complete 24-hr dosing interval for each dosage schedule under carefully controlled conditions. The different TheoDur regimens did not affect the 24-hr group average FEV1.0, PEF, MMEF or FVC. However, statistically significant circadian variation in airways function existed irrespective of the drug dosing schedule. Airways patency and FVC were least overnight (0200-0500 hr) and best during the morning or afternoon. With regard to FEV1.0 and PEF, which evidenced group circadian change for BID and OD-PM regimen by Cosinor analysis, the peak-to-trough (double amplitude) difference expressed as a percentage of the 24-hr average was rather large, being greatest for the OD-PM schedule (20.5% for FEV1.0 and 24.3% for PEF). The data for the 10 participants revealed individual differences in the effectiveness of the 3 studied theophylline dosing regimens when assessed in terms of the mean level and stability of airways function over the 24 hr. Based on the findings, neither the BID, OD-PM nor the OD-AM regimen effectively moderated the nocturnal deterioration of pulmonary function suggesting theophylline as dosed and timed may not be as efficacious as desired for patients with a history of strictly nighttime dyspnea. Thus, the schedule and prescription of TheoDur must take into account differences between patients, including the time when asthma symptoms are most likely to be experienced by each.

Comparison of once-daily evening versus morning sustained-release theophylline dosing for nocturnal asthma

Eight diurnally active (approximately 0730-1100 hr) adults (41-61 yr) suffering from nocturnal asthma volunteered for a double-blind, cross-over randomized study of a once-daily dosing (600-900 mg/24 hr) of Armophylline (Rorer s.a., France), a sustained-release theophylline given either at 0800 hr or 2000 hr for 8-day durations. Study variables monitored daily were: (a) self-measured peak expiratory flow (PEF), heart rate, oral temperature and self-rated fatigue checked every 2 hr during the waking span as well as upon spontaneous nocturnal awakenings and (b) duration and subjective characteristics of sleep rated every morning. In addition, serum theophylline concentration (STC) plus the variables in (a) were sampled every 2 hr during the 24 hr of the eighth day of each timed treatment span. Rx at 0800 hr was associated with a nocturnal dip in PEF of 20 +/- 2.8% (X +/- S.E.M.) from the level achieved at the time of the diurnal crest; Rx at 2000 hr moderated the nocturnal fall; it was only 10 +/- 2.1% and within the physiologic limits of non-asthmatic persons. The STC peak height (Cmax) was greater (P less than 0.05) and time-to-peak (Tmax) shorter (P less than 0.005) with Rx at 0800 hr than at 2000 hr. With Rx at 2000 hr an STC plateau of approximately 12 hr resulted. A statistically significant correlation (r = 0.86; P less than 0.01) between PEF and the corresponding-in-time STC was observed with Rx at 2000 hr but not with Rx at 0800 hr. A small, but statistically significant, higher heart rate resulted from 2000 hr dosings in five out of eight subjects relative to the 0800 hr dosing. There were no differences in the sleep characteristics nor in oral temperature between dosing times. Once-daily (600-900 mg) SRT dosing at 2000 hr controlled the nocturnal dip of bronchial patency with no major side-effects in diurnally active adult patients with nocturnal allergic asthma.

Administration-time-dependency of the pharmacokinetic behavior and therapeutic effect of a once-a-day theophylline in asthmatic children

Using a double-blind, placebo-control, crossover study design, 8 asthmatic children (8-15 years) were evaluated for temporal patterns in airways function throughout separate study periods when treatment was placebo or Theo-24 once-daily on separate occasions at 0600, 1500 or 2100 hr. During 39-hr in-hospital observations, pulmonary function and serum theophylline concentrations (STC) were assessed every 3 hr under all treatments. The pharmacokinetics of Theo-24 varied greatly depending on the dosing time. For the afternoon and evening dosings, the Cmax, Tmax, AUC, % swing, % fluctuation, % AUC fluctuation, % nocturnal excess and Cav(2-6 hr) were all statistically significantly greater than for the morning dosing. Compared with the placebo regimen, dosing patients with Theo-24 at 1500 hr disrupted circadian patterns of airways function, especially airways patency, while dosing at 2100 hr, reduced the amplitude and shifted the acrophase of several spirometric measures to a slightly earlier time. Theo-24 treatment irrespective of dosing time resulted in comparable enhancement of the group 24-hr mean, minimum and maximum values of airways patency with reference to placebo baselines. Theo-24 dosing at 1500 or 2100 hr, however, resulted in the best effect on the airways as assessed by the 24-hr mean FEV 1.0 level in 7 of the 8 asthmatic children. When the drug was given at 1500 hr, the time of lowest FEV 1.0 was shifted from the nighttime hours in 5 of 8 patients. These findings suggest that clinicians need to individualize the theophylline dosing schedule of patients to best control the symptoms of asthma.

Sustained-release theophylline and nocturnal asthma, once-daily and unequal dosing schedules

Many asthmatic patients experience aggravation of symptoms overnight resulting in disruption of their sleep. Sustained-release theophylline represents at this time a major bronchodilator medication which possesses a sufficient duration of activity to avert the nocturnal breathing distress of asthma. Circadian rhythm-adapted theophylline schedules consisting of unequal dosing--more or all the drug taken in the evening--have proven efficacious in clinical investigations for certain patients. Although the kinetic behavior of some formulations is affected by food, the circadian rhythm-adapted schedules represent a significant step forward toward the goal of optimizating sustained-release theophyllines for patients who experience nighttime symptoms.

Treatment of asthma by a controlled-release theophylline tablet formulation: a review of the North American experience with nocturnal dosing

As many as 80 percent of asthmatics experience nighttime or early-morning episodes, which are difficult to treat and potentially fatal. The greater-than-normal amplitude of circadian airflow variation in many asthmatics contributes heavily to the genesis of the early 'morning dip'. Beta-agonists and corticosteroids are of limited usefulness in nocturnal asthma, and slow-release theophylline drugs, while potentially effective, vary in 24-hr blood profile and hence their influence on nocturnal episodes. Traditional 12-hr 'symmetric' theophylline regimens, instead of meeting increased nocturnal demands, may actually produce lower night- than daytime blood levels. On the other hand, appropriately timed administration of a once-daily theophylline drug might provide maximum blood levels when needed and help stabilize 24-hr airflow. Accumulated data, summarized in this review, demonstrate the chronotherapeutic potential of single-daily evening doses of a controlled-release theophylline preparation (Uniphyl 400-mg tablets) in nocturnal and early morning asthma. Nighttime blood concentrations with this regimen were higher than were those with Theo-Dur tablets, B.I.D., in the same total daily doses, or with once-daily morning Uniphyl administration. In fed and fasted subjects, evening administration of Uniphyl 400-mg tablets was well tolerated and did not lead to 'dose dumping.' Clinically, this treatment demonstrated advantages over B.I.D. theophylline, over single-daily morning regimens, and over prior theophylline therapy. Advantages of the evening regimen included better early-morning airflow (without significant decline later in the day), more effective symptom control, better patient acceptance, fewer night awakenings, and the obvious convenience of once-daily dosing. In addition, lung function showed greater stability, throughout the day, with once-daily evening therapy than with traditional 12 hr dosing. Uniphyl 400-mg tablets may be administered once daily to provide maximum blood levels at the time of peak bronchoconstriction, whether at night or during the day.

Chronobiology and asthma. II. Body-time-dependent differences in the kinetics and effects of bronchodilator medications

Several bronchodilator medications exhibit body-time (i.e., biological rhythm)-dependent changes in their pharmacokinetics and effects. Epinephrine (Adrenalin), metaproterenol (orciprenaline), aminophylline, and ipratropium bromide all have a better effect on the tone of the airways during the night and/or morning, when bronchial patency is low, than during the day, when it is high. The pharmacokinetics of sustained-release theophyllines (SRTs) exhibit administration-time differences. Day-night dosing-time differences in the kinetics of theophylline are especially prominent in children. Generally, in day-active asthmatic children the absorption of SRT is more rapid after a morning than an evening dosing. The administration-time effect on the kinetics of SRTs also is apparent in adult patients, but the magnitude of difference between the day versus evening administrations apparently is more moderate. Initial findings from studies of unequal (morning versus evening) BID dosing schedules--more theophylline or terbutaline before bed-time than arising--reveal a better therapeutic advantage relative to equal BID dosing schedules for those patients with predominantly nocturnal symptoms. Once-daily (OD) SRTs intended for delivery of the entire daily dose at a single time also differ quantitatively in their chronokinetics. Since asthma is mainly a nocturnal disease in many patients, it has been recommended by many that ODSRTs be taken in the evening. If taken in the morning, as is the current practice in the United States, they may not ensure therapeutic theophylline blood levels during the night when most needed. Moreover, not all ODSRTs appear suitable for once-nightly administration because of unacceptable kinetics.

Therapeutic advantage of unequal dosing of theophylline in patients with nocturnal asthma

Two theophylline treatments were compared in a randomized, multiple-dose, crossover study on 20 patients present with nonallergic bronchial asthma. Both products (E = Euphyllin CR, A = Afonilum Retard) were capsules containing micropellets. They were administered according to the recommendations of the manufactures and differed in the total daily theophylline dose (642 mg versus 500 mg), the partition of this dose (1/3 in the morning and 2/3 in the evening versus equal amounts in the morning and evening) and the timing of the evening dose (2200 hr versus 2000 hr). The patients were off oral theophyllines at least 2 days prior to study onset and no other drugs were allowed to be administered during the testing periods. On the 4th day of each study period, serum theophylline concentrations (STC) and peak expiratory flow rate (PEF) were determined every 2 hr. Compared with the 24-hr PEF reference profile taken prior to study onset, both theophylline treatments produced a significantly higher 24-hr PEF average (mesor). Treatment E resulted in significantly higher mesor than A; in addition, the PEF amplitude relative to the mesor was reduced by treatment E when compared with placebo.

Steady state pharmacokinetics, metabolism and pharmacodynamics of theophylline in children after unequal twice-daily dosing of a new sustained-release formulation

This was an open-label study in 19 children aged 9-13 years, weighing 27-44 kg, with bronchial asthma. Twenty-four-hour steady-state concentrations of theophylline and its metabolites 1,3-dimethyl uric acid, 3-methyl xanthine and 1-methyl uric acid were assessed after daily dosing of 600 mg (ca 18 mg/kg/day) of the sustained-release theophylline micro-pellet sprinkle system BY158K, for 4 days. The dosing regimen used was an unequal twice-daily dose of 200 mg in the morning after breakfast and 400 mg in the evening after dinner. Twenty-four-hour peak expiratory flow (PEF) profiles were compared before treatment and at steady-state, along with lung function parameters after bronchial provocation. Mean values +/- SD (n = 16) of the steady-state characteristics were Cmin 6.8 +/- 2.1 mg/l, Cmax 14.5 +/- 4.8 mg/l and Cav 10.5 +/- 2.9 mg/l, the plateau time was 11.7 +/- 4.8 hr and peak-trough fluctuation and swing were 72 +/- 21 and 118 +/- 52%, respectively. There was an excellent reproducibility of theophylline pre-dose levels at corresponding time points of the 24-hr sampling period [r = 0.864 (p less than 0.001)]. Mean values +/- SD of the 24 hr average serum metabolite levels were 0.9 +/- 0.2 mg/1 for 1,3-dimethyl uric acid, 0.6 +/- 0.1 mg/1 for 3-methyl xanthine and 0.4 +/- 0.1 mg/1 for l-methyl uric acid. Lung function (n = 17) following bronchial provocation, improved in 10 children after theophylline treatment of 4 days, remained stable in 2 patients and deteriorated in 5 patients. Serum theophylline profiles and PEF profiles ran largely in parallel over the 24-hr period. Six children exhibited typical theophylline induced side-effects, headache (n = 3), nausea (n = 4), dizziness (n = 1), vomiting (n = 4), sleep disturbances (n = 1), pallor (n = 1) and tremor (n = 1), necessitating in 3 children one dose omission/reduction (n = 2) or subsequent dose reduction (n = 1). It has been shown that a twice daily dosing regimen with unequal doses of anhydrous theophylline (BY158K) is well suited to this population of fast metabolisers. The patients were well protected throughout the day, including the critical early morning hours.

Chrono-optimization of the time of evening administration with unequally divided twice-daily theophylline

The effect of different times of evening administration (2000 hr versus 2200 hr) of sustained-release aminophylline (Euphyllin CR) on pharmacokinetics and lung functions was investigated in 30 patients presenting with moderately severe asthma. The study protocol followed a randomized three-period change-over design including a placebo period. As the dosing of the investigated SR-formulation is circadian rhythm adapted, the major part of the daily dose, namely 2/3, is affected by the change in time of administration. With regard to the nocturnal peak expiratory flow (PEF), no statistically significant difference between the times of evening administration was detected. However, the concomitant requirement for corticosteroids and inhaled beta-2-mimetics complicates the assessment of the relative clinical efficacy of the major dosing of theophylline during the 24 hr even though this drug is usually not given as a monotherapy in severe patients with reversible airway obstruction.

Treatment of nocturnal asthma: the role of sustained-release theophylline and oral beta-2-mimetics

In two double-blind, multiple-dose cross-over studies the therapeutic effects of SR theophylline preparations given once each night (mean 11.2 mg/kg per day) versus twice daily in equal doses (mean 10.3 mg/kg per day) (study I) and SR-terbutaline in equal doses (mean 0.25 mg/kg per day) versus SR theophylline in unequally divided daily doses (mean 5.3 mg/kg morning dose, 10.6 mg/kg evening dose) study II) were compared in 19 patients with nocturnal asthma. At the end of each treatment period drug serum concentrations and PEFR were measured every 2 hr over a 24-hr period. With the twice-daily, equally divided regimen, serum theophylline concentrations were lower at night than during the day (mean 9.4 +/- 0.9 versus 11.3 +/- 1.0 mg/l). With the single evening administration, serum theophylline concentrations were considerably higher at night (Cmax 16.3 +/- 1.4 mg/l) and the circadian variation of PEFR was significantly reduced. PEFR was higher during night and early morning (283 +/- 14 versus 217 +/- 11 l/min, P less than 0.005). During daytime in study II, PEFR values were slightly higher with theophylline than terbutaline. There was no significant difference in peak flow between either treatment during the night and early morning. However, additional use of inhaled beta-2-mimetics because of asthmatic attacks occurred more often during terbutaline (79 times in 8/10 patients) than theophylline treatment (29 times in 5/10 patients). Symptom scores, number of attacks and side-effects clearly favor the theophylline regimen. We conclude that for patients with nocturnal asthma a once-nightly dose of SR theophylline can be sufficient for stabilization of the airways.

Reduction of nocturnal asthma by an inhaled anticholinergic drug

Although the mechanisms of nocturnal asthma are still uncertain, increased vagal cholinergic tone may be contributory factor. To examine this hypothesis, we have studied the effect of an anticholinergic drug, oxitropium bromide, on the early morning fall in peak expiratory flow (PEF) in patients with nocturnal asthma. Eighteen patients (aged 18 to 76 years; seven men) with documented nocturnal asthma were studied in a double-blind randomized cross-over study in which they received either oxitropium bromide (200 micrograms or 400 micrograms) or placebo in a single dose at night for two-week periods. With placebo the mean (+/- SE) fall in PEF (expressed as percentage of evening PEF) was 17.3 +/- 2.0 percent, which was significantly reduced to 10.3 +/- 3.3 percent after oxitropium (400 micrograms) (p less than 0.05; ANOVA). Closer analysis revealed that nine of the 18 patients had responded in a dose-dependent manner, with the mean percentage decreases with placebo, 200 micrograms, and 400 micrograms of oxitropium being 19.1 +/- 3.2, 11.5 +/- 4.4, and 5.0 +/- 4.5 percent, respectively (p less than 0.01 between each treatment). The remaining patients were unaffected by therapy. There were no differences between "responders" and "non-responders" in terms of age, atopic status, duration of asthma, severity of asthma, or bronchodilator response to albuterol (salbutamol). There were no differences in nocturnal symptoms between periods of treatment, and no side effects were recorded. We conclude that anticholinergic drugs may protect against nocturnal asthma in some patients, indicating the involvement of vagal cholinergic mechanisms.

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.

Once daily theophylline in childhood asthma

A new sustained-release theophylline preparation has been designed with the purpose of providing 24-hour protection against bronchospasm in asthmatics when given as a single dose. Fifteen children with moderate asthma completed a double-blind, placebo-controlled crossover trial of this product given once a day before bed. There was a significant fall in night symptoms (P less than 0.05), a rise in the mean early morning peak expiratory flow rate (PEFR) (P less than 0.01) and a fall in the number of mornings on which PEFR was less than 2 SD under the mean for height (P less than 0.01). An improvement in mean day symptom scores and evening PEFR was not significant. Thus we have shown that this product given once a day before bed is suitable for this way.

Circadian variation in airway function

Nocturnal asthma is a common and troublesome problem. Many possible mechanisms have been proposed, including exposure to allergens, sleep itself, the supine posture, withdrawal of bronchodilator drugs, gastric reflux, mucus plugging, and airway cooling. Although these may be contributory factors in individual patients, they cannot provide a universal explanation for the phenomenon of nocturnal and early morning wheezing. It now seems that nocturnal asthma may best be understood in terms of circadian rhythms. A circadian variation in airway caliber has been demonstrated in normal subjects; in asthmatic subjects, the same rhythm is present but with greater amplitude. The amplitude is magnified by bronchial hyper-responsiveness, a cardinal feature of asthma. Evidence now suggests that the fall in circulating epinephrine level at night removes an important defense against bronchoconstriction in asthmatic subjects, and this itself may be magnified by removal of the braking effect of epinephrine on mast cell mediator release. In addition, increased vagal reflex bronchoconstriction and the delayed effects of the fall in plasma cortisol level may also contribute to nocturnal wheezing. Thus, nocturnal asthma may be explained by a complex interaction of several coincident circadian rhythms, which produce only small changes in airway caliber in normal subjects; however, in asthmatic patients, these constrictor effects are magnified to produce bronchospasm severe enough to wake the patient.

Comparison of morning versus evening dosing with a new once-daily oral theophylline formulation

A double-blind, cross-over comparison of morning (8 A.M.) versus evening (10 P.M.) dosing regimens with a new once-daily oral theophylline (Uniphyl, Purdue Frederick) was performed. The comparison was based upon steady-state theophylline pharmacokinetics, spirometric measurements over 24 hours, the patients' quantitative reporting of asthmatic symptoms, and medication side effects. No statistically significant differences were observed in any theophylline parameter between the dosing regimens. Evening dosing, but not morning dosing, resulted in a significant attenuation of the early morning dip in pulmonary function. The morning severity of wheezing, chest tightness, and shortness of breath was significantly reduced after evening dosing. Overall no difference in the incidence of symptoms was noted. No significant differences in side effects were noted. Evening dosing with Uniphyl produced a significant improvement in morning pulmonary function, and this benefit was subjectively noted by the patients. No decline in this benefit was noted later in the day. Evening dosing with Uniphyl clearly is superior to morning dosing.

Pharmacokinetics and clinical response to single- and multiple-dose sustained-release theophylline compounds in perennial bronchial asthma

Nine adult subjects with perennial bronchial asthma participated in a single-blind, cross-over, placebo-controlled study to evaluate and compare the effectiveness of a 24-hour sustained-release theophylline formulation, Uniphyl, with that of a twice-daily compound, Theo-Dur. The subjects took each drug for two weeks and monitored peak expiratory flow and recorded their symptoms in a diary three times daily. At the end of each experimental period, they were hospitalized for 24 hours for determination of the pharmacokinetics of the compound they were taking and the relationship between fluctuations in theophylline blood levels and changes in pulmonary mechanics. Both drugs were highly effective, and no significant differences between formulations were found in any aspects of the study. The results demonstrate that a single daily dose of Uniphyl is an efficacious form of therapy for controlling perennial asthma in adults.

Nocturnal asthma and timing of treatment

Nocturnal deterioration of pulmonary function in asthmatic patients is a well-recognized and well-documented phenomenon. The mechanism of this "morning dip," however, remains uncertain. Although the circadian rhythms of body temperature, corticosteroid, catecholamine, histamine, and opiate peptide levels, and even sleep itself have been shown to be in phase with the diurnal variation in asthma, a causal relationship has yet to be established. Increased nighttime bronchial reactivity to histamine, acetylcholine, and house dust allergen have been demonstrated. In general, continuous treatment with theophylline, beta-adrenergic agonists, or corticosteroids attenuates the degree of morning dip but does not completely eliminate the circadian rhythm of asthma. The significance of nocturnal asthma is emphasized by the observation that asthma deaths occur more frequently during nighttime hours and are often preceded by large daily swings in peak expiratory flow. Further studies examining the etiology and treatment of nocturnal asthma are needed.

Methylxanthine therapy and reversible airway obstruction

Theophylline is a medium-potency bronchodilator that is useful in the treatment of reversible airway obstruction from any cause. It also improves contraction of the diaphragm, accelerates mucociliary transport, lowers pulmonary artery pressures, and limits the release of the mediators of immediate hypersensitivity from mast cells. The pharmacologic effects correlate closely with the plasma concentration of this drug, and within the defined therapeutic limits, only minor adverse effects occur. The dose of theophylline required to achieve therapeutic plasma levels varies considerably between subjects, mainly because of differences in clearance. The latter varies with age, smoking, alterations in hepatic function, cardiac failure, viral infections, and concurrent administration of other drugs. For the treatment of acute symptoms, either intravenous administration or a rapidly absorbed compound such as uncoated tablets or liquids is required. For the long-term management of reversible airway obstruction, sustained-release theophyllines are available. These formulations maintain therapeutic serum theophylline concentrations for prolonged periods, permitting longer dosing intervals and improved patient compliance.

Sustained release choline theophyllinate in nocturnal asthma

Nocturnal wheeze is common in patients with asthma, and slow release theophyllines may reduce symptoms. As theophyllines are stimulants of the central nervous system the effect of 10 days' twice daily treatment with sustained release choline theophyllinate or placebo on symptoms, overnight bronchoconstriction, nocturnal oxygen saturation, and quality of sleep were studied in a double blind crossover study in nine stable patients with nocturnal asthma (five men, four women, age range 23-64 years; forced expiratory volume in one second (FEV1) 0.85-3.8 1; vital capacity 1.95-6.1 1). When treated with the active drug all patients had plasma theophylline concentrations of at least 28 mmol/l (5 micrograms/ml) (peak plasma theophylline concentrations 50-144 mmol/l (9-26 micrograms/ml]. Morning FEV1 was higher when treated with sustained release choline theophyllinate (2.7 (SEM 0.3) 1) than placebo (2.1 (0.3) 1) (p less than 0.01). Both daytime and nocturnal symptoms were reduced when the patients were treated with sustained release choline theophyllinate and subjective quality of sleep was improved (p less than 0.002). When treated with the active drug, however, quality of sleep determined by electroencephalography deteriorated with an increase in wakefulness and drowsiness (p less than 0.05) and a reduction in non-rapid eye movement sleep (p less than 0.005). Treatment with choline theophyllinate had no effect on either the occurrence or the severity of transient nocturnal hypoxaemic episodes or apnoeas or hypopnoeas. In conclusion, sustained release choline theophyllinate prevents overnight bronchoconstriction, but impairs quality of sleep defined by electroencephalography.

Characteristics and prognostic value of morning dipping of peak expiratory flow rate in stable asthmatic subjects

Characteristics and prognostic relevance of morning dip of peak expiratory flow rate (PEFR) were evaluated in stable asthmatic subjects. Among 246 outpatients monitored four times daily for two weeks, 38 (group A) showed a significant difference between morning reading of PEFR and each of the others; they were compared to 38 randomly selected patients (group B) not showing morning dip in PEFR. Less frequent seasonal course, extrinsic pathogenesis, and sensitization to mites characterized group A; starting airflow limitation was more severe in those with morning dip, but no significant difference between mean PEFR measured throughout two weeks was found. At 6 to 12 weeks, morning dip was not found in 19 of 38 subjects in group A and appeared in seven of 38 subjects in group B, with no clearcut relationship to treatment being evident. At 25 to 104 weeks, no significant difference between therapeutic requirements and the forced expiratory volume in one second was detected; therefore, unlike the short-term, morning dip is not a risk factor for worse long-term prognosis.

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.

Treatment of nocturnal asthma in children with a single dose of sustained-release theophylline taken after supper

In a placebo-controlled, double-blind cross-over study of 2 X 3 weeks' duration, twenty-four children with stable asthma who were wheezing during the night, were treated with a single dose of sustained-release theophylline (SRT) taken after supper. The mean serum theophylline levels 4 and 12 hr after dosing were 7.7 and 11.2 mg/l, respectively. Few side-effects were seen. The mean morning peak expiratory flow (PEF) was significantly higher during SRT treatment (244 +/- 11 1/min) than during placebo treatment (207 +/- 121/min) (P less than 0.001). The mean difference between morning and evening PEF was reduced from 20.7 to 8.6% by treatment with SRT (P less than 0.001). Theophylline significantly reduced the severity of attacks of bronchoconstriction during the night as judged by PEF measurement and use of extra bronchodilator treatment per attack. The response to inhaled terbutaline was increased during SRT treatment compared with that in the placebo period, however pre-treatment PEF did differ significantly between the two periods. The number of acute asthma attacks during the night, the number of symptom-free nights and the use of extra bronchodilators during the night were all significantly improved by SRT treatment (P less than 0.001). Seventeen children correctly identified the SRT period whilst six children showed no preference for either period. A single dose of SRT taken after supper is an effective treatment for nocturnal asthma in children.

Sustained release theophylline in nocturnal asthma

Twice daily sustained release theophylline gave satisfactory steady serum theophylline concentrations in asthmatic children aged 7 to 14 years. The children showed improvement in symptoms, less frequent waking at night, reduced use of beta agonist inhalers, and improved early morning peak flows while being treated with this preparation. There was no improvement in peak flow at other times, but the patients recorded increased use of beta agonists during the placebo period.

Once a day theophylline; serum concentrations

Twenty four hour profiles of serum theophylline concentrations were examined in 15 asthmatic children taking a new theophylline preparation once a day. Peak concentrations occurred at a time when nocturnal wheezing is likely. Fluctuation in concentrations throughout the day was greater than with other currently available preparations, but the importance of this has yet to be determined.

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

Circadian variation in plasma theophylline concentrations was studied in eight patients with obstructive airways disease during regular 12-hourly dosing at 09.00 and 21.00 h with a sustained-release theophylline formulation. After regular dosing for a minimum period of 3 days, plasma concentration measurements were made at 09.00, 13.00, 21.00 and 01.00 h on 3 consecutive days and at more regular intervals during a complete 24 h period on day 4. On each day, theophylline concentrations for the first 4 h of the dosing interval were consistently higher during the day than at night. However, the differences were significant only at 13.00/01.00 h on day 2, and for each of the first 4 h on day 4. On day 4, following the dose at 21.00 h the mean peak plasma theophylline concentration occurred 6.9 +/- 0.8 h after dosing; in contrast, after the morning dose the mean peak concentration occurred at 4.5 +/- 0.8 h. However, the mean 'steady-state' concentrations during the two dose intervals were not significantly different. Thus circadian variations in plasma drug concentrations do occur in patients taking maintenance theophylline therapy: differing rates of absorption may account for the observed pattern.

Subcutaneous terbutaline and control of brittle asthma or appreciable morning dipping

In a pilot study two patients with brittle asthma and two with morning dipping received terbutaline or a placebo administered subcutaneously either by continuous infusion or in injections every six hours. In two patients brittle asthma was completely suppressed by terbutaline 1 mg/day given by either method. In the two others early morning dipping responded only to continuous subcutaneous infusions of terbutaline 12 mg/day. Terbutaline administered subcutaneously may be an effective treatment in asthmatic patients who show important diurnal variations in air flow.

Inhaled therapy reduces morning dips in asthma

14 asthmatic patients with nocturnal symptoms and morning dips in peak expiratory flow rate (PEFR) were treated with regular inhaled salbutamol for 1 or 2 weeks, followed by regular inhaled beclomethasone dipropionate, in addition to salbutamol, for a further 2 weeks. Mean PEFR rose to normal values in all but 1 patient. Morning dips in PEFR were substantially reduced in 8 patients. There was an equivalent rise in mean PEFR in the other 6 patients, but their morning dips did not improve. Inhaled salbutamol reduced the dips in the responsive patients, but addition of inhaled steroid produced further improvement. Inhaled beta agonist alone improved mean PEFR in these patients, but inhaled steroids produced most of the improvement in the other subgroup. No patient experienced side-effects. Thus mean PEFR can be improved and morning dips in PEFR reduced in a high proportion of asthmatic patients by the use of regular inhaled therapy without resorting to less-well-tolerated oral agents.