Circadian variation in adrenergic responses in asthmatic subjects

Circadian rhythms of risk factors and management in atherosclerotic and hypertensive vascular disease: Modern chronobiological perspectives of an ancient disease

Atherosclerosis, a chronic inflammatory disease of the arteries that appears to have been as prevalent in ancient as in modern civilizations, is predisposing to life-threatening and life-ending cardiac and vascular complications, such as myocardial and cerebral infarctions. The pathogenesis of atherosclerosis involves intima plaque buildup caused by vascular endothelial dysfunction, cholesterol deposition, smooth muscle proliferation, inflammatory cell infiltration and connective tissue accumulation. Hypertension is an independent and controllable risk factor for atherosclerotic cardiovascular disease (CVD). Conversely, atherosclerosis hardens the arterial wall and raises arterial blood pressure. Many CVD patients experience both atherosclerosis and hypertension and are prescribed medications to concurrently mitigate the two disease conditions. A substantial number of publications document that many pathophysiological changes caused by atherosclerosis and hypertension occur in a manner dependent upon circadian clocks or clock gene products. This article reviews progress in the research of circadian regulation of vascular cell function, inflammation, hemostasis and atherothrombosis. In particular, it delineates the relationship of circadian organization with signal transduction and activation of the renin-angiotensin-aldosterone system as well as disturbance of the sleep/wake circadian rhythm, as exemplified by shift work, metabolic syndromes and obstructive sleep apnea (OSA), as promoters and mechanisms of atherogenesis and risk for non-fatal and fatal CVD outcomes. This article additionally updates advances in the clinical management of key biological processes of atherosclerosis to optimally achieve suppression of atherogenesis through chronotherapeutic control of atherogenic/hypertensive pathological sequelae.

The endogenous circadian system worsens asthma at night independent of sleep and other daily behavioral or environmental cycles

Asthma often worsens at night. To determine if the endogenous circadian system contributes to the nocturnal worsening of asthma, independent of sleep and other behavioral and environmental day/night cycles, we studied patients with asthma (without steroid use) over 3 wk in an ambulatory setting (with combined circadian, environmental, and behavioral effects) and across the circadian cycle in two complementary laboratory protocols performed in dim light, which separated circadian from environmental and behavioral effects: 1) a 38-h "constant routine," with continuous wakefulness, constant posture, 2-hourly isocaloric snacks, and 2) a 196-h "forced desynchrony" incorporating seven identical recurring 28-h sleep/wake cycles with all behaviors evenly scheduled across the circadian cycle. Indices of pulmonary function varied across the day in the ambulatory setting, and both laboratory protocols revealed significant circadian rhythms, with lowest function during the biological night, around 4:00 AM, uncovering a nocturnal exacerbation of asthma usually unnoticed or hidden by the presence of sleep. We also discovered a circadian rhythm in symptom-based rescue bronchodilator use (β2-adrenergic agonist inhaler) whereby inhaler use was four times more likely during the circadian night than day. There were additive influences on asthma from the circadian system plus sleep and other behavioral or environmental effects. Individuals with the lowest average pulmonary function tended to have the largest daily circadian variations and the largest behavioral cycle effects on asthma. When sleep was modeled to occur at night, the summed circadian, behavioral/environmental cycle effects almost perfectly matched the ambulatory data. Thus, the circadian system contributes to the common nocturnal worsening of asthma, implying that internal biological time should be considered for optimal therapy.

Overnight Changes in Lung Function of Obese Patients with Obstructive Sleep Apnoea

PURPOSE

Obstructive sleep apnoea (OSA) is a prevalent disorder, characterised by collapse of the upper airways during sleep. The impact of sleep-disordered breathing on pulmonary function indices is however currently not well described. The aim of the study was to evaluate diurnal change in lung function indices in a cohort of patients with OSA and relate pulmonary function changes to disease severity.

METHODS

42 patients with OSA and 73 healthy control subjects participated in the study. Asthma and COPD were excluded in all volunteers following a clinical and spirometric assessment. Spirometry was then performed in all subjects in the evening and the morning following a polysomnography study.

RESULTS

There was no difference in evening or morning FEV₁ or FVC between patients and control subjects (p > 0.05). Neither FEV₁ nor FVC changed in control subjects overnight (p > 0.05). In contrast, FEV₁ significantly increased from evening (2.18/1.54-4.46/L) to morning measurement (2.26/1.42-4.63/L) in OSA without any change in FVC. The FEV₁ increase in OSA was related to male gender, obesity and the lack of treatment with statins or β-blockers (all p < 0.05). A tendency for a direct correlation was apparent between overnight FEV₁ change and RDI (p = 0.05, r = 0.30).

CONCLUSIONS

Diurnal variations in spirometric indices occur in patients with OSA and FEV₁ appears to increase in subjects with OSA overnight. These changes occur in the absence of change in FVC and are directly related to the severity of OSA. These findings dictate a need to consider time of lung function measurement.

[Not Available]

The Optimal Dosing Times of Corticoids. The therapeutic use of Cortisol and its derivatives, anti-inflammatory corticoids, sets delicate problems to resolve because of Cortisol's physiological roles and its circadian rhythms. Cortisol and the majority of its derivatives have desirable and undesirable effects that are time-related administration. The chronothera- peutic optimisation to increase desirable effects and safety of corticoids is shown in the treatment of adrenocortical failure, congenital adrenal hyperplasia and asthma. The knowledge of physiological and physiopathological rhythms of asthma permitted to realize oral treatment optimisation by using a number of corticoids. This knowledge puts in a prominent position the advantages of ciclesonide: a new inhaled corticoid. A chronobiologic approach could be used in a classic optimisation which involves a molecule modification and inhalation like routes of administration.

Chronobiology and chronotherapy of allergic rhinitis and bronchial asthma

Study of the chronobiology of allergic rhinitis (AR) and bronchial asthma (BA) and the chronopharmacology and chronotherapy of the medications used in their treatment began five decades ago. AR is an inflammatory disease of the upper airway tissue with hypersensitivity to specific environmental antigens, resulting in further local inflammation, vasomotor changes, and mucus hypersecretion. Symptoms include sneezing, nasal congestion, and runny and itchy nose. Approximately 25% of children and 40% of adults in USA are affected by AR during one or more seasons of the year. The manifestation and severity of AR symptoms exhibit prominent 24-h variation; in most persons they are worse overnight or early in the morning and often comprise nighttime sleep, resulting in poor daytime quality of life, compromised school and work performance, and irritability and moodiness. BA is also an inflammatory medical condition of the lower airways characterized by hypersensitivity to specific environmental antigens, resulting in greater local inflammation as well as bronchoconstriction, vasomotor change, and mucus hypersecretion. In USA an estimated 6.5 million children and 15.7 million adults have BA. The onset and worsening of BA are signaled by chest wheeze and/or croupy cough and difficult and labored breathing. Like AR, BA is primarily a nighttime medical condition. AR is treated with H1-antagonist, decongestant, and anti-inflammatory (glucocorticoid and leukotriene receptor antagonist and modifier) medications. Only H1-antagonist AR medications have been studied for their chronopharmacology and potential chronotherapy. BA is treated with some of the same medications and also theophylline and beta2-agonists. The chronopharmacology and chronotherapy of many classes of BA medications have been explored. This article reviews the rather extensive knowledge of the chronobiology of AR and BA and the chronopharmacology and chronotherapy of the various medications used in their treatment.

Response to nonprescription epinephrine inhaler during nocturnal asthma

BACKGROUND

Many health care professionals believe that a nonprescription epinephrine metered-dose inhaler is less effective and shorter acting and has more cardiovascular adverse effects than prescription beta2-agonists.

OBJECTIVE

To determine if increasing the epinephrine dose improves efficacy safely.

METHODS

Eight patients with nocturnal asthma (age range, 20-46 years) were treated in a randomized, crossover manner on 2 different nights while sleeping in a clinical research center. On awakening from asthma symptoms, 2, 4, and 8 actuations of epinephrine or albuterol were administered at 17-minute intervals (14 cumulative actuations). Forced expiratory volume in 1 second (FEV1), asthma symptoms, and systemic effects were measured before the first dose, during the 9- to 17-minute period after each dose, and 30 minutes after the last dose.

RESULTS

The mean +/- SD FEV1 at the onset of symptoms was 45% +/- 11% and 44% +/- 12% predicted before epinephrine and albuterol, respectively, and increased to a maximum of 86% +/- 11% and 93% +/- 10%, respectively (P = .04). Symptoms decreased as FEV1 improved and did not return after either treatment; 6 patients were symptom free after 14 cumulative actuations of epinephrine compared with 6 cumulative actuations of albuterol. Heart rate decreased to 71 +/- 10/min after epinephrine but increased to 92 +/- 14/min after albuterol (P = .001). After the last dose, serum potassium concentration was 3.6 +/- 0.3 micromol/L after epinephrine and 3.2 +/- 0.4 micromol/L after albuterol (P = .01).

CONCLUSION

Epinephrine was nearly as effective as albuterol in terminating an acute episode of airway obstruction but without cardiovascular effects in these otherwise healthy young adults.

Effect of ozagrel hydrochloride, a thromboxane synthetase inhibitor, on alcoholic beverage-induced bronchoconstriction in asthmatic patients

Acetaldehyde is thought to be a main factor of alcohol-induced asthma. The thromboxane (TX) synthetase inhibitor, ozagrel hydrochloride, inhibits acetaldehyde-induced bronchoconstriction in asthmatic patients. The present study evaluated the involvement of TXA(2) on alcoholic beverage-induced bronchoconstriction. Four patients with alcohol-induced asthma received ozagrel (400 mg for 4 days) or placebo using a single-blind, randomized, cross-over design. On two separate study days, each subject drank the same brand and volume of alcoholic beverage (beer or Japanese sake) and bronchoconstriction was assessed as the change in peak expiratory flow (PEF). The effect of ozagrel on the aerosolized challenge of acetaldehyde was investigated in the same subjects. Although aerosolized acetaldehyde-induced bronchoconstriction was significantly prevented by ozagrel, there were no differences in the time course of the decrease in PEF or the maximum fall in PEF after alcohol intake between placebo and ozagrel. We conclude that TXA(2) is not involved in alcoholic beverage-induced bronchoconstriction.

Prevalence and mechanisms of development of asthma and airway hyperresponsiveness in athletes

A high prevalence of asthma and airway hyperresponsiveness (AHR) has been reported in the athlete population. Factors potentially predisposing athletes to these conditions have not been clearly identified. Although moderate exercise has been shown to be beneficial in patients with asthma, repeated high-intensity exercise could possibly contribute to the development of asthma and AHR. This report provides an overview of the prevalence and possible mechanisms of development of asthma and AHR in the athlete population. The prevalence of asthma and AHR are higher in athletes than in the general population, particularly in swimmers and athletes performing sports in cold air environments. Possible mechanisms involved in the development of asthma in athletes are still uncertain; however, the content and physical characteristics of the inhaled air seem to be important factors, while immune and neurohumoral influences could play a modulatory role. This report stresses the need for further studies to better define the aetiologic factors and mechanisms involved in the development of asthma and AHR in athletes, and proposes relevant preventive and therapeutic measures.

Adrenergic airway vascular smooth muscle responsiveness in healthy and asthmatic subjects

The purpose of the present study was to determine the responsiveness of airway vascular smooth muscle (AVSM) as assessed by airway mucosal blood flow (Qaw) to inhaled methoxamine (alpha(1)-agonist; 0.6-2.3 mg) and albuterol (beta(2)-agonist; 0.2-1.2 mg) in healthy [n = 11; forced expiratory volume in 1 s, 92 +/- 4 (SE) % of predicted] and asthmatic (n = 11, mean forced expiratory volume in 1 s, 81 +/- 5%) adults. Mean baseline values for Qaw were 43.8 +/- 0.7 and 54.3 +/- 0.8 microl. min(-1). ml(-1) of anatomic dead space in healthy and asthmatic subjects, respectively (P < 0.05). After methoxamine inhalation, the maximal mean change in Qaw was -13.5 +/- 1.0 microl. min(-1). ml(-1) in asthmatic and -7.1 +/- 2.1 microl. min(-1). ml(-1) in healthy subjects (P < 0.05). After albuterol, the mean maximal change in Qaw was 3.0 +/- 0.8 microl. min(-1). ml(-1) in asthmatic and 14.0 +/- 1.1 microl. min(-1). ml(-1) in healthy subjects (P < 0.05). These results demonstrate that the contractile response of AVSM to alpha(1)-adrenoceptor activation is enhanced and the dilator response of AVSM to beta(2)-adrenoceptor activation is blunted in asthmatic subjects.

Airway hyperresponsiveness in elite athletes

It has been suggested that high-level training could contribute to the development of airway hyperresponsiveness (AHR), but the comparative effects of different sports on airway function remains to be determined. We evaluated 150 nonsmoking volunteers 18 to 55 yr of age; 100 athletes divided into four subgroups of 25 subjects each according to the predominant estimated hydrocaloric characteristic of ambient air inhaled during training: dry air (DA), cold air (CA), humid air (HA) and a mixture of dry and humid air (MA), and 50 sedentary subjects. Each subject had a respiratory questionnaire, a methacholine challenge, allergy skin-prick tests, and heart rate variability recording for evaluation of parasympathetic tone. The athletes had a 49% prevalence of AHR (PC(20) < 16 mg/ml), with a mean PC(20) of 16.9 mg/ml, compared with 28% (PC(20): 35.4) in sedentary subjects (p = 0.009). The prevalence (%) of AHR and mean PC(20) (mg/ml) varied as followed in the four subgroups of athletes: DA: 32% and 30.9; CA: 52% and 15.8; HA: 76% and 7.3; and MA: 32% and 21.5 (p = 0.002). The estimated parasympathetic tone was higher in athletes (p < 0.001), but this parameter showed only a weak correlation with PC(20) (r = -0.17, p = 0.04). This study has shown a significantly higher prevalence of AHR in athletes than in the control group because of the higher prevalence in the CA and HA groups. Parasympathetic activity may act as modulator of airway responsiveness, but the increased prevalence of AHR in our athlete population may be related to the type and possibly the content of inhaled air during training.

Circadian rhythms in the pharmacokinetics and clinical effects of beta-agonist, theophylline, and anticholinergic medications in the treatment of nocturnal asthma

Published asthma consensus reports now acknowledge that asthma is a nocturnal disease in as many as 75% of those afflicted by this medical condition. Nonetheless, the treatment of this chronic obstructive pulmonary disease in the clinic continues to be based primarily on homeostatic considerations in that it relies on long-acting bronchodilator and other therapies formulated and scheduled to ensure constant or near-constant levels of medication during the 24h. The need of asthma patients prone to nighttime attacks is not the same during the day and night; the therapeutic requirements of patients who experience nocturnal asthma, especially ones with the more severe forms of the disease, are often not satisfied by conventional medications. The therapeutic response and patient tolerance to bronchodilator medications can be improved markedly when the medications are proportioned during the 24h as a chronotherapy, that is, when more medication is delivered during nighttime sleep than daytime activity, as verified by numerous studies. This article reviews how the body's circadian rhythms influence the pharmacokinetics and effects of commonly prescribed asthma therapies and addresses why and how they must be taken into consideration to increase the effectiveness of asthma treatment.

Biologic rhythms in the immune system

In all of its components, the immune system shows regularly recurring, rhythmic variations in numerous frequencies; the circadian (about 24 h) rhythms are the best explored. The circadian variations in immunocompetent cells circulating in the peripheral blood are of a magnitude to require attention in medical diagnostics. Both the humoral arm and the delayed (cellular) arm of the immune system function in a rhythmic manner. The response of the immune system to introduction of an antigen and to challenge of the sensitized organism varies in extent in the circadian frequency range and also in lower frequencies, for example, of about a week (circaseptan) or seasonally (circannual). The medical application of the biologic rhythms of the immune system extends to diagnostic measures, as well as treatment.

Clinical chronobiology and chronotherapeutics with applications to asthma

The concept of homeostasis (i.e., constancy of the milieu interne) has long dominated the teaching and practice of medicine. Concepts and findings from chronobiology, the scientific study of biological rhythms, challenge this construct. Biological processes and functions are not at all constant; rather, they are organized in time as rhythms with period lengths that range in duration from as short as a second or less to as long as a year. It is the body's circadian (24 h) rhythms that have been researched most intensely. The peak and trough of these rhythms are ordered rather precisely in time to support the biological requirements of activity during the day and sleep at night. The timing of the peak and trough plus the magnitude of variation (amplitude) of physiological and biochemical functions during the 24 h give rise to predictable-in-time, day-night patterns in the manifestation and exacerbation of many common medical conditions. Circadian rhythms also can influence the response of patients to diagnostic tests and therapeutic interventions according to their timing with reference to body rhythms. Rhythms in the pathophysiology of medical conditions and patient tolerance to medications constitute the basis for chronotherapeutics, the timing of treatment in relation to biological rhythm determinants as a means of optimizing beneficial effects and safety. The article discusses recent advances in medical chronobiology and chronotherapeutics and their relevance to clinical medicine in general and the management of asthma in particular. Indeed, since asthma is a disease that exhibits rather profound circadian rhythmicity, investigation of its pathophysiology and therapy necessitates a chronobiologic approach.

Bambuterol in the treatment of asthma. A placebo-controlled comparison of once-daily morning vs evening administration

Once-daily morning (7 AM) vs evening (10 PM) administration of the terbutaline prodrug bambuterol (20-mg tablet dose) was investigated in a double-blind, cross-over, randomized, and placebo-controlled study involving 29 diurnally active patients with asthma. Terbutaline plasma concentration, spirometry, and drug tolerance were assessed during 39-h inpatient studies. A 7-day washout period separated each treatment. Mean 24-h plasma concentration was comparable for morning and evening bambuterol (13.2 vs 14.0 nmol/L). The Cmax for evening vs morning dosing was 17.2 vs 15.5 nmol/L (p < 0.02). The 24-h mean FEV1 was greater (p < 0.001) for bambuterol (morning: 3.2 L; evening: 3.4 L) vs placebo (2.9 L) as it was for FVC, FEF25-75%, and peak expiratory flow rate (PEFR), with the maximum effect at 4 AM independent of medication time. Evening dosing, however, resulted in greatest 7 AM (awakening) FEV1, FEV25-75, and PEFR (p < 0.03). With reference to corresponding-in-time placebo values, improvement in FEV1 at the end of the 24-h dosing intervals amounted to 0.34 L (13.5%) (p < 0.0004) and 0.35 L (15.9%) (p < 0.0012) with evening and morning bambuterol dosing, respectively. Side effects were greater for bambuterol than placebo, but not significantly so. Once-daily bambuterol therapy proved to be an effective treatment for asthma, whether administered in the evening or morning. Evening dosing seems best for nocturnal asthma since airway patency overnight and on awakening at 7 AM is most improved.

Potentiating effect of inhaled acetaldehyde on bronchial responsiveness to methacholine in asthmatic subjects

BACKGROUND

It has recently been reported that acetaldehyde induces bronchoconstriction indirectly via histamine release. However, no study has been performed to assess whether acetaldehyde worsens bronchial responsiveness in asthmatic subjects so this hypothesis was tested.

METHODS

Methacholine provocation was performed on three occasions: (1) after pretreatment with oral placebo and inhaled saline (P-S day), (2) after placebo and inhaled acetaldehyde (P-A day), and (3) after a potent histamine H1 receptor antagonist terfenadine and acetaldehyde (T-A day) in a double blind, randomised, crossover fashion. Nine asthmatic subjects inhaled 0.8 mg/ml acetaldehyde or saline for four minutes. After each inhalation a methacholine provocation test was performed.

RESULTS

Methacholine concentrations producing a 20% fall in FEV1 (PC20-MCh) on the P-A day (0.48 mg/ml, 95% CI 0.21 to 1.08) and T-A day (0.41 mg/ml, 95% CI 0.22 to 0.77) were lower than those on the P-S day (0.85 mg/ml, 95% CI 0.47 to 1.54). There was no change in the PC20-MCh between the P-A and T-A days. A correlation was observed between the logarithmic values of PC20-MCh (log PC20-MCh) on the P-S day and the potentiating effect of acetaldehyde on the methacholine responsiveness [(log PC20-MCh on P-A day)-(log PC20-MCh on P-S day)] (rho = 0.82).

CONCLUSIONS

Acetaldehyde induces bronchial hyperresponsiveness in patients with asthma by mechanisms other than histamine release.

Chronopharmacology of albuterol in hospitalized asthmatic children

Eleven children (8-16 years old) hospitalized for acute bronchospasm were included in this investigation. Throughout the study, the children received the standardized course of therapy for hospitalized asthmatics with corticosteroids and albuterol nebulizations. Children receiving ipratropium were excluded from the study. Spirometric measurements, including forced expiratory volume in 1 s (FEV1), were made immediately before and 30 min after each albuterol nebulization over a 24-h period. The well-known temporal changes in FEV1 were observed in patients suffering from nocturnal asthma (NA): basal values were maximal at midday (10 a.m. to 2 p.m.) and lowest in the evening or at night (10 p.m. to 6 a.m.). This 24-h variation in lung function was not found in children without nocturnal exacerbations of their asthma. A 24-h variation was also observed in albuterol-induced bronchodilation in patients with NA: maximal effectiveness occurred at night, and lower effect was obtained with the midday administration. The albuterol-induced increases in FEV1 were not clinically significant in children without nocturnal asthma except when the beta 2-agonist was inhaled between 10 p.m. and 2 a.m. The data suggest that patients with nonnocturnal asthma might have different drug requirements than those with nocturnal symptoms.

Nocturnal asthma: approach to the patient

Nocturnal asthma can be diagnosed by asking patients whether they awaken at night with asthmatic symptoms and feel the need to use an aerosol bronchodilator. The primary objective in treating nocturnal asthma is to help patients sleep through the night. The bronchoconstriction that underlies nocturnal asthmatic symptoms is a reflection of bronchial hyperresponsiveness, and this hyperresponsiveness is greatly increased by airway inflammation. In patients with allergic asthma, airway inflammation can be reduced by reducing exposure to allergens and, in some cases, by immunotherapy. Nocturnal bronchoconstriction is best controlled by scheduling sustained-release bronchodilators, particularly theophylline, to provide the maximal theophylline blood concentration at the time of maximal obstruction, usually between 4:00 and 6:00 A.M.

Pathogenesis and pathophysiology of nocturnal asthma

Nocturnal wheezing is a major component of asthma. This article reviews the many factors (allergen exposure, sleep, airway cooling, diminished clearance of mucous secretions) that have been identified as contributing to nocturnal asthma. Also discussed are recent data suggesting that diurnal variations in hormone concentrations and in autonomic nervous system control are possible mechanisms of nocturnal asthma. Decreased epinephrine secretion and increased vagal tone during sleep not only cause airway obstruction but may also enhance bronchial reactivity. These changes in the modulation of airway smooth muscle tone produce bronchial obstruction, which, in turn, accentuates ventilation-perfusion mismatch and increases hypoxia.

Circadian rhythm in total pulmonary resistance of asthmatic children. Effects of a beta-agonist agent

Six children (boys and girls, 8 to 13 years old) with allergic asthma (AA) had their total pulmonary resistance (R1) measured at four fixed times (0730, 1130, 1630 and 2230 hr), before and again 10 min after a 2 mg orciprenaline (beta-agonist) aerosol inhalation. R1 was measured by means of the esophageal balloon technique. Subjects were socially synchronized in May with a diurnal activity from 0700 to 2100 and a nocturnal rest. Patients had had no asthma attacks and had received no medication for 8-15 days. Time series were analyzed according to conventional (t-tested mean time point differences) ANOVA, and cosinor methods. The 24 hr adjusted means (cm H2O.l/s +/- SEM) were 5.7 +- 0.4 in seven previously documented healthy children. 7.4 +/- 1.2 in AA before orciprenaline, and 4.9 +/- 0.2 in healthy children, 5.2 +/- 0.8 in AA after beta-agonist inhalation. Circadian rhythms were detected in both groups before but not after treatment. The treatment had its maximal effect on R1 around 0730 (when bronchial patency is close to its trough) and had no effect around 1630 (peak time of airway patency) in both groups (P less than 0.01; ANOVA). Thus, inhaled orciprenaline was mainly effective around 0730 and to a lesser extent around 2230 whereas there was no detectable effect during the day (1230 and 1630).

Day-night patterns in bronchial patency and dyspnea: basis for once-daily and unequally divided twice-daily theophylline dosing schedules

Asthma typically worsens overnight. Although 24-hr variation in environmental conditions may contribute to the worsening of dyspnea at night, this does not fully explain day-night patterns of this disease. Circadian (about 24-hr) rhythms in bioprocesses which influence airways patency constitute major contributory factors. The nighttime exacerbation of asthma may represent the influence of circadian bioperiodicities in bronchial patency, airways hyperreactivity to acetylcholine, histamine and house dust, and altered levels of several plasma constituents such as cortisol, epinephrine, histamine and cyclic AMP.

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.

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.

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.

Diurnal variation of dynamic compliance, resistance and viscous work of breathing in normal horses and horses with lung disorders

Dynamic compliance, airway resistance, viscous work and respiratory frequency were measured at intervals in horses over 12 h periods. Variation, daily averages and circadian patterns were recorded. Examinations were performed on 24 horses. They were divided into three groups: Normal horses, horses with chronic latent bronchitis and horses with manifest chronic obstructive pulmonary disease (COPD). Significant differences were found between the daily averages and the fluctuations when the normal group and the COPD group were compared. In most cases differences between all three groups were significant. A significant circadian rhythm for airway resistance was detected in diseased horses. It was also established that single measurements give an incomplete picture of lung function. As has been established in humans, analysis of fluctuations in respiratory mechanics may be of diagnostic value. The above results should be taken into account particularly in trials with bronchodilators in horses with COPD.

Chronobiology and asthma. I. Day-night differences in bronchial patency and dyspnea and circadian rhythm dependencies

The symptoms of allergic asthmatic patients typically worsen during the night, especially during the early morning hours. Although 24-hour variations in the environment contribute to the intensification of the asthmatic condition nocturnally, environmental changes themselves do not fully explain the temporal aspects of this disease. Circadian (about 24-hour) rhythms in critical bioprocesses constitute significant contributory factors. The exacerbation of asthma during the night represents the changing status of biological functioning due to circadian rhythms in bronchial patency; airways hyperreactivity to acetylcholine, histamine, and house dust; and plasma cortisol, epinephrine, histamine, and cyclic AMP, among others.

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.

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.

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.

Effect of naloxone on circadian rhythms in lung function

To determine whether the endogenous opioid peptides play a part in the pathogenesis of asthmatic morning dipping, six patients with chronic asthma with a reproducible peak flow pattern of morning dipping were investigated in a double blind, randomised, crossover study of naloxone versus placebo. Naloxone was given as a loading dose of 8 mg followed by a continuous infusion of 5.6 mg/h from midnight until 10 am on two consecutive nights. Naloxone had no significant effect on PEFR, FEV1, or FVC at 6 am. There was, however, an improvement over placebo values in all these indices between the hours of 8 am and 8 pm on the day after the first naloxone infusion in all six patients. This effect was not observed after the second naloxone infusion.