Caffeine bronchial effects

A much milder and legal stimulant is caffeine, depicted in Figure 14.27. A number of mechanisms have been proposed for caffeines stimulatory effects. Perhaps the most straightforward mechanism is caffeine s facilitating of the release of norepinephrine into synaptic clefts. Caffeine also exerts many other effects on the body, such as dilation of arteries, relaxation of bronchial and gastrointestinal muscles, diuretic action on the kidneys, and stimulation of stomach-acid secretion. 

Breathing rate increases in response to caffeine. The effect on respiration occurs at the level of the brain stem s respiration control center. Theophylline has the most potent action of all the methylxanthines, affecting the smooth muscle of the bronchial tree in the lungs. This is why theophylline is a treatment for asthma. Doctors may recommend weak tea for their asthmatic patients with colds this bronchodilating action of the theophylline in the tea will aid in clearing mucus. 

Caffeine has been shown to have a bronchial and smooth muscle relaxant effect and to improve skeletal muscle contractility. Significant increases in hand tremor and forearm extensor electromyogram were observed in human subjects after the ingestion of 6mgkg of caffeine. This effect is more likely due to a CNS stimulatory effect than to direct action on the muscle fibers. Skeletal muscle fatigue can be reversed by high concentrations of caffeine obtained only in vitro but not in vivo. 

These compounds competitively inhibit phosphodiesterase, resulting in an increase in cyclic AMP (see Box 14.3) and subsequent release of adrenaline. This leads to the major effects a stimulation of the central nervous system (CNS), a relaxation of bronchial smooth muscle, and induction of diuresis. These effects vary in the three compounds. Caffeine is the best CNS stimulant, and has weak diuretic action. Theobromine has little stimulant action, but has more diuretic activity and also muscle relaxant properties. Theophylline also has low stimulant action and is an effective diuretic, but it relaxes smooth muscle better than caffeine or theobromine. 

Caffeine and the related dimethylxanthines have similar pharmacological or therapeutic effects and similar toxic effects. The primary actions include stimulation of the central nervous system, relaxation of bronchial muscles, mild cardiac muscle stimulation, and diuretic effects on the kidney. 

Methylxanthines have a number of other effects, including effects on smooth muscles and the cardiovascular system. The most notable effect on smooth muscles is relaxing the bronchi of the lungs. Theophylline is prescribed to treat mild forms of asthma. While both caffeine and theophylline will relax the bronchial smooth muscles, theophylline is used therapeutically because of its longer half-life. This allows the drug to stay in the therapeutic range longer. 

Caffeine is a widely used CNS stimulant. Theophylline hK some medical use as a CNS stimulant, but its CNS-iiimulant properties are encountered more often as somc-iimes severe, and potentially life-threatening, side effects of its Use in bronchial asthma therapy. Theobromine has very iitIcCNS activity (probably because of pour physicochemi-iil properties for di.stributiun to the CNS). 

The important use of theophylline and its preparations in bronchial asthma is discu.ssed elsewhere. Caffeine also is reported to have valuable brunchodilating properties in asthma. Finally, because of central vasoconstrictive effects, caffeine has value in treating migraine and tension headaches and truly have actual analgesic properties in (he latter use. 

Theophylline Cellular mech like caffeine. More CNS stimulation than caffeine. Increased cardiac stimulation and diuresis. More effective bronchodilator. Bronchial asthma. Apnea and bradycardia in premature infants (unlabeled use). II M... 

Because of the bronchial muscle relaxant effect, caffeine is used in chronic obstructive pulmonary disease and for the treatment of asthma. The use of caffeine in the treatment of children with minimal brain dysfunction, to increase the duration of electroconvulsive therapy-induced seizure, for allergic rhinitis, as well as for atopic dermatitis has also been described. Recently, caffeine has been used as a diagnostic test for malignant hyperthermia and in the diagnosis of neuroleptic malignant syndrome, a complication of neuroleptic therapy. 

Caffeine and theophylline are methylxanthine derivatives that are widely distributed in plant products and beverages. Theophylline and caffeine have been widely used for the treatment of asthmatic manifestations, neonatal apnea and bronchial spasms. However, these compounds produce the biological effect of dieresis, and excessive intake leads to many undesired side effects, with symptoms including tremors, excessively fast heartbeat and gastrointestinal difficulties [35]. Therefore, it is very important to determine accurately the content of these alkaloids in foods and pharmaceutical preparations. 

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