The longterm treatment of an asthmatic patient using phentolamine

Importance of Alpha-adrenergic Receptor Subtypes in Regulating of Airways Tonus at Patients with Bronchial Asthma

Background:

In this work, effect of Tamsulosin hydrochloride as antagonist of alpha_1A and alpha_1B- adrenergic receptor and effect of Salbutamol as agonist of beta₂- adrenergic receptor in patients with bronchial asthma and increased bronchial reactibility was studied.

Methods:

Parameters of the lung function are determined by Body plethysmography. Raw and ITGV were registered and specific resistance (SRaw) was also calculated. Tamsulosin was administered in per os way as a preparation in the form of the capsules with a brand name of “Prolosin”, producer: Niche Generics Limited, Hitchin, Herts.

Results:

Results gained from this research show that blockage of alpha_1A and alpha_1B- adrenergic receptor with Tamsulosin hydrochloride (0.4 mg and 0.8 mg in per os way) has not changed significantly (p > 0.1) the bronchomotor tonus of tracheobronchial tree in comparison to the inhalation of Salbutamol as agonist of beta₂- adrenergic receptor (2 inh. x 0.2 mg), (p < 0.05). Arterial blood pressure showed no significant decrease following the administration of the dose of 0.8 mg Tamsulosin.

Conclusion:

This suggests that the activity of alpha_1A and alpha_1B- adrenergic receptor in the smooth musculature is not a primary mechanism which causes reaction in patients with increased bronchial reactibility, in comparison to agonists of beta₂ – adrenergic receptor which emphasizes their significant action in the reduction of specific resistance of airways.

Response of the adrenergic system after provoked bronchoconstriction in patients with bronchial asthma

Objective:

In this paper, effect of the Tolazoline as antagonist of the alpha-₂ adrenergic receptors in patients with bronchial asthma and chronic obstructive bronchitis was studied, and also the effect of stimulation with Hexoprenaline of beta-₂ adrenergic receptor after bronchi-constriction caused with Propranolol, and Acetylcholine.

Methods:

Lung function parameters are determined with Body plethysmography. In patients with bronchial asthma and chronic obstructive bronchitis was registered resistance (Raw), was determined the amount of intrathoracic gas volume (ITGV), and specific resistance was calculated as well (SRaw). Aerosolization was done with standard aerosolizing machine-Asema.

Results:

The study included a total of 21 patients. Two hours after the inhalation of Propranolol, in experimental group, it was applied the blocker of alpha-₂ adrenergic receptors (Tolazoline 20 mg / ml with inhalator ways), which did not cause changes in bronchomotor tonus of tracheobronchial system (p > 1.0). Meanwhile, at the same patient, stimulation of beta-₂ adrenergic receptor with Hexoprenaline (2 inh x 0.2 mg) is associated with a significant decrease of the specific resistance of airways (SRaw, p < 0.01). Control group results show that after bronchi-constriction caused by Propranolol-aerosol (20 mg / ml) in patients with bronchial asthma and chronic obstructive bronchitis, an increase of specific resistance in airways was caused (SRaw, p < 0.01), which confirms the presence of hyper-reactive bronco-constrictor effects intermediated by vagal ways. Two hours after Propranolol, inhaled Hexorenaline has blocked the action of Propranolol, but not entirely. Furthermore, two hours after acetylcholine-aerosol (1 mg /ml) was applied, inhaled Ipratropium (2 inh x 1 mg) has fully blocked the action of chemical bronchoconstrictor mediators, causing a decline of specific resistance in the airways (SRaw; p < 0.01).

Conclusion:

This suggests that primary mechanism, which would cause reaction in patients with increased bronchial reactibility, is prevalence of the cholinergic system over adrenergic one, and not the relationship in between alpha-₂ and beta-₂ adrenergic receptors.

Influence of alpha-adrenoceptor blockade on antigen- and propranolol-induced bronchoconstriction in guinea-pigs in vivo

1. Beta-adrenoceptor antagonists, such as propranolol, can provoke severe bronchoconstriction only in asthmatic subjects. Recently, we developed a guinea-pig model of propranolol-induced bronchoconstriction (PIB) and the purpose of this study was to investigate the role of alpha-adrenergic nerve pathways in this reaction. 2. Phentolamine administered after an antigen challenge did not inhibit PIB; however, its administration before the antigen challenge significantly inhibited the antigen-induced bronchoconstriction and also bronchoconstriction induced by methacholine inhalation. 3. We conclude that the alpha-adrenergic nerve system is not involved in the development of PIB following allergic reaction in our guinea-pig model.

A refractory type asthmatic whose symptoms markedly improved by midaglizole

We present a patient with refractory intrinsic asthma who showed a good response to both a single oral dose and a 4-week period of administration of the selective alpha-2 adrenoceptor antagonist, midaglizole. After the single dose, bronchodilation was immediately observed. With continuous administration, the peak expiratory flow rate (PEFR) was increased and the total daily intake of aerosol was decreased in a dose-dependent fashion. These results suggest that the addition of midaglizole to the usual antiasthmatic agents can be of value in the management of refractory asthma.

The functional conversion hypothesis: a contributor to exercise-induced asthma?

Studies on receptor stability suggest that functional conversion of adrenoceptors between alpha and beta can occur in mammalian myocardium due to variations in the environment such as temperature changes, pH or hormonal changes. If adrenoceptors of the respiratory system behave similarly, heat and water loss of airways noted during hyperventilation could lead to functional loss of inhibitory beta and expression of excitatory alpha adrenoceptors. This would have the effect of counter-action of adrenergic homeostatic mechanisms which may be of particular importance in asthmatic subjects. The hypothesis of adrenoceptor interconversion could contribute to the airway obstruction observed during exercise in asthmatics. This concept is supported by scattered reports of the efficacy of alpha adrenergic antagonists in preventing exercise-induced asthma.

Cholinergic and neurogenic mechanisms in obstructive airways disease

Although primary neural control of airway function is through parasympathetic pathways, more recent evidence indicates that there are important adrenergic and non-adrenergic, non-cholinergic neural mechanisms that may also influence respiratory function. The parasympathetic nervous system component includes neural receptors in the airways as well as afferent and efferent pathways that travel in the vagus nerves. Afferent vagal sensory receptors mediate the response to irritant or rapidly adapting receptor activation, Hering-Breuer, and the unmyelinated "C" fibers or "J" receptor pathways. The motor component of the parasympathetic nervous system has several important functions that regulate tone in normal system has several important functions that regulate tone in normal and obstructed airways. These pathways affect the following respiratory structures: bronchial smooth muscle; the mucociliary system; the larynx; and the nose. Finally, the parasympathetic nervous system may play a role in some species in the control of breathing and in the hyperpneic responses associated with airflow obstruction. In addition to cholinergic neural mechanisms, bronchomotor tone may also be influenced by adrenergic mechanisms and non-adrenergic, non-cholinergic neural pathways. Although there is minimal innervation of the airways by the sympathetic nervous system, there is ample evidence that beta-adrenoreceptors are present on bronchial smooth muscle. Beta-receptor stimulation not only relaxes airway smooth muscle, but also inhibits mediator release from mast cells in the airways and may alter vascular permeability. Alpha-adrenoreceptors are found in human airways and stimulation of these receptors causes bronchoconstriction. Although the importance of alpha-adrenoreceptors has been questioned, recent evidence suggests that alpha stimulation may play a role in cold air- and exercise-induced asthma. Finally, non-adrenergic, non-cholinergic nerves have been shown to cause relaxation of human airways in in vivo studies. There is increasing evidence that vasoactive intestinal peptide and peptide histidine methanol are the mediators of these responses. More recently, other neuropeptides (substance P, neurokinin A, and calcitonin gene-related peptide) have been localized in nerves in airways. These cause bronchoconstriction in vitro and may be released from afferent nerve terminals by an axon reflex. Although the precise role of these substances in controlling airway tone and bronchial secretions in humans is not fully understood, they may have important modulatory effects on the neural control of airway function.

Comparison between an alpha-adrenergic antagonist and a beta 2-adrenergic agonist in bronchial asthma

Fifteen patients suffering from asthma received inhalations of phentolamine, albuterol (salbutamol), a combination of phentolamine and albuterol, and placebo, in a single-blind fashion; the changes in the pulmonary function tests were recorded over a three-hour period. Three patients responded to phentolamine with marked bronchodilatation, whereas severe bronchoconstriction was induced by the drug in two patients. Five patients improved more with phentolamine than with placebo, while all patients improved more markedly with albuterol and still more following inhalation of the combination of both drugs. As a group, there were no statistically significant differences between the responses to phentolamine compared with placebo, or between albuterol alone compared with the combination of both drugs. We concluded that both alpha-antagonist and beta 2-agonist agents act in the same direction in most patients, the beta 2-agonist being the dominant. These results do not offer convincing proof that enhanced alpha-adrenergic activity is the main bronchoconstrictor mechanism even in those few with good response to phentolamine, who also showed very good responsiveness to albuterol. The mechanism of phentolamine-induced bronchoconstriction was discussed, but in the light of presently accepted theories, we were unable to evolve a reasonable explanation.

Adrenoceptors: molecular nature and role in atopic diseases

Since Szentivanyi proposed the idea that asthma and other atopic diseases are due to a beta adrenergic defect there has been much interest in the role of the adrenergic receptors in allergy. The radioactive ligand binding techniques developed within the last few years have greatly increased our knowledge concerning the molecular nature of the adrenoceptors and the events following receptor stimulation. The adrenoceptors have shown to be very dynamic structures. Their number and affinity may be altered due to various physiological and pharmacological stimuli. Their role in the pathogenesis of atopic diseases has not been definitely settled, but there seem to be a true beta adrenergic hyporesponsiveness and alpha hyperresponsiveness in asthma. This article briefly describes the radioligand binding technique and summarizes our present knowledge of the nature of the alpha and beta adrenoceptors and their possible role in atopic diseases.

Comparison of vaccination of mice and rats with Haemophilus influenzae and Bordetella pertussis as models of atopy

1. Rats and mice were vaccinated with Haemophilus influenzae in different vaccination schedules whereafter blood eosinophils were counted. In rats a single vaccination resulted in a dose-dependent effect on the blood eosinophil count in a pattern comparable with that after Bordetella pertussis vaccination. In a long-term vaccination schedule (five times a week for 5 weeks) rats developed a constant eosinophilia. In mice a single vaccination resulted in an eosinopenia of a consistent pattern which differed from the response after Bordetella pertussis vaccination; in a long-term vaccination schedule, eosinophilia was evoked for a period of about 13 days. 2. Thirty minutes after an adrenaline injection in vaccinated rats and mice with Haemophilus influenzae, hyperglycaemic and eosinophilic responses were measured. The eosinophilic response after adrenaline was inhibited in both species; the hyperglycaemic response in rats was unaltered, in mice the response was slightly but significantly (P less than 0.05) decreased. 3. The sensitivity to several drugs was tested in mice, 5 days after vaccination with Haemophilus influenzae or Bordetella pertussis. Haemophilus influenzae vaccination reduced the isoprenaline sensitivity and increased the noradrenaline sensitivity. Bordetella pertussis vaccination reduced the isoprenaline sensitivity while the sensitivity to histamine and adrenaline was raised. 4. The Haemophilus influenzae vaccinated experimental animal provides a model that is possibly more related to human atopy than the Bordetella pertussis vaccinated animal.

Irreversibility of obstructive changes in severe asthma in childhood

The findings in three children with severe asthma are presented. Following intensive round-the-clock therapy with theophylline (the dosage of which maintained serum levels of theophylline between 10 microgram/ml and 20 microgram/ml) and therapy with prednisone (20 mg twice daily for three weeks or more), there were improvements in spirometric and body plethysmographic measurements. Despite this therapy, abnormalities in the forced expiratory volume in one second, the maximal midexpiratory flow, the residual volume, and specific airway conductance remained. These cases represent a subgroup of asthmatic children with reactive airways who have an irreversible component to their disease.

Asthma in adults: the ambulatory patient

Heterogeneity is the hallmark of adult asthma, and patients thus need individualized therapeutic programs. But there are unifying underlying mechanisms, understanding of which makes it easier to design the clinical stategy appropriate to each case.

Adrenergic responses of asthmatic and normal subjects to submaximal and maximal work levels

The response of the adrenergic system of asthmatic subjects to exercise and the role of plasma catecholamines in exercise-induced asthma were investigated. Plasma levels of norepinephrine and epinephrine were measured at rest, during and after exercise in 7 asthmatic and 9 matched normal subjects. Exercise-induced bronchospasm occurred in all asthmatic subjects following exercise, while no significant change was observed in the normal subjects. The results showed that plasma levels of norepinephrine and epinephrine at rest and changes that occcurred during and after exercise were similar in both normal and asthmatic subjects. These data suggest that the adrenergic response of asthmatics to the same relative exercise stress as reflected in plasma catecholamine levels does not differ from that of normal subjects. It appears that changes in the circulating catecholamines do not play a significant role in the pathogenesis of exercised-induced asthma.

Effect of bronkosol and its components on cardiopulmonary parameters in asthmatic patients

Bronkosol and its components, isoetharine hydrochloride and phenylephrine hydrochloride, were compared in a double-blind randomized fashion for their effect on pulmonary and cardiovascular parameters in patients with reversible bronchospasm. Bronkosol and isoetharine produced significant bronchodilatation as measured by forced expiratory volume in one second (FEV), forced vital capacity (FVC), and mean forced expiratory flow during the middle half of the FVC (isovolume FEF 25% to 75%), and phenylephrine did not. There was no difference between Bronkosol and isoetharine in the degree or duration of bronchodilatation. Significantly more patients had to "discontinue" after 15 min on the day of testing with phenylephrine than with Bronkosol or isoetharine. Heart rate was not increased after Bronkosol or isoetharine, confirming its selective beta-2 action. The addition of phenylephrine to isoetharine had no beneficial effect on oxygen saturation. There was no significant difference between these drugs in systolic and diastolic blood pressure, pulse, or respiration. The results of this study cast doubt on the useful contribution of phenylephrine in Bronkosol.

Exercise-induced asthma--clinical, physiological, and therapeutic implications

Exercise provokes acute airways obstruction, maximum shortly after stopping, in virtually all asthmatic patients. The severity of this exercise-induced asthma (EIA) depends upon the type of exercise, with running being the most asthmogenic, swimming and walking the least, and cycling intermediate even with the same metabolic stress. The duration and severity of the exercise also affect the amount of EIA, the maximum amount of being obtained after 6 to 8 min of running hard enough to raise the heart rate to 180 beats per minute (bpm) in children or 140 bpm in adults. EIA is not the result of hyperventilation or blood gas changes and appears to depend on the release of relatively short-lived transmitter agents during the exercise period. EIA can be prevented by premedication with bronchodilators, especially with sympathomimetics. Cromolyn sodium is not a bronchodilator but inhibits EIA in most subjects if given before the exercise. EIA can also be inhibited by atropine and alpha adrenergic blockers in some patients, but by steroids in only a minority of cases. Exercise testing provides a good model for study of the physiology and pharmacology of clinical asthma, and is some guide to prognosis, but it must be properly standardized and the important differences must be appreciated.