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Plants Used for Respiratory Problems - II . Theophylline. Two types of bronchodilators. Adrenergic agents Increase the volume and diameter of bronchial smooth muscles by relaxing them Include norepinephrine, epinephrine, and ephedrine Theophylline drugs
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Plants Used for Respiratory Problems - II Theophylline
Two types of bronchodilators • Adrenergic agents • Increase the volume and diameter of bronchial smooth muscles by relaxing them • Include norepinephrine, epinephrine, and ephedrine • Theophylline drugs • Act on the bronchial muscles to relieve air way obstruction, increase coronary blood flow and stimulate respiration
Theophylline • Natural component in tea that finds pharmaceutical use as a bronchodilator, vasodilator, and a smooth muscle relaxant
Tea • From tip leaves of Camellia sinensis • Shrub or small tree native to Tibet, India, China, and Burma. • Still largely grown in this region of the world • Caffeine, theophylline, tannins and theol contribute to flavors and stimulating properties
Value of tea • Stimulating effects of tea due to caffeine and theophylline present • Although there is some concern about caffeine intake, people who drink large amounts of green tea have low rates of cancer • Animal studies have shown that rates of breast and prostate cancer reduced by consumption of green tea - attributed to polyphenols in green tea
Theophylline • When caffeine metabolized in body, a small amount is actually converted to theophylline • Theophylline used to treat asthma since 1930s by directly relaxing the smooth muscles of the bronchial airways - thereby opening constricted airways • This bronchodilating action helps relieve wheezing, coughing, etc
Theophylline • Purine alkaloid • Also called a methyl xanthine alkaloid • Originally extracted from tea • Now chemically synthesized
Theophylline • Popular asthma drug for many years • One of first long term bronchodilators • Several trade names and is available in a variety of forms: Theo-Dur, Slo-Bid, Aminophylline are a few of the commonly known medications
Side Effects • Theophylline can become toxic • Difference between a therapeutic level and a toxic level is narrow • Side Effects include tachycardia, palpitations, nausea, GI upset, headache, insomnia, arrhythmias, convulsions, urticaria, erythema, dermatitis • Theophylline must also be used with caution in patients with cardiovascular disease, hypertension, or hepatic or renal insufficiency
History of theophylline use • Became standard treatment in 1930s • Use declined substantially since 1980s upon realization of the importance of the inflammatory component of asthma • Use of a Beta-2 agonist coupled with steroids became standard management tools • Also concerns about side effects • Theophylline removed from OTC oral medications - inhaled still allowed in 1995
Treatment options • Anti-inflammatory effects of inhaled steroids became preferred treatment • For many patients these reduced need for other drugs • However long-term effects of inhaled steroids still unknown • Recent studies show that when used with inhaled steroids, theophylline improves lung function - not just brochodilation
Theophylline back in picture?? • Study involved patients with persistent cough, wheeze, or breathlessness despite daily use of inhaled steroids • Patients who received theophylline improved peak flow rates and other measures of lung function • Results showed that therapy combining low dose theophylline with low-dose inhaled steroids is as effective as using high dose steroids alone and avoided side effects
How theophylline works • Dilation and relaxation of constricted airways • Increased contraction strength of the diaphragm • Increased beat frequency of the respiratory cilia • Central Nervous System stimulation • Diuretic effects
Dilation and relaxation of constricted airways • Main reason for using theophylline • By relaxing the airway muscles, airways enlarge • In asthma, breathing becomes easier • In conditions where fluid or other material has accumulated in airways, dilation of the airways can suppress coughing
More on dilation and relaxation • Smooth muscles surround the small airways and, when constricted, narrow airways • Theophylline inhibits cAMP phosphodiesterase, which causes the breakdown of cyclic AMP • Cyclic AMP causes smooth muscle relaxation • By inhibiting cAMP phosphodiesterase, there's more cyclic AMP around to relax smooth muscles
Increased contraction strength of the diaphragm • The diaphragm forms the muscular floor of the chest cavity and its contractions correspond to the strength of breathing motions • When breathing becomes difficult, this muscle works harder against the resistance created by disease • Theophylline can strengthen the diaphragm
Increased beat frequency of the respiratory cilia • Cells secrete a layer of mucus which captures debris we have inhaled and move debris formed by disease lower down in the lungs • Mucus is moved to throat by cilia on epithelial cells lining respiratory tract - cilia move the mucus and its trapped debris • Once the mucus reaches the throat it is either coughed up or swallowed • Theophylline helps cilia to beat faster and thereby more rapidly clear respiratory debris
Central Nervous System stimulation • Stimulating effects of theophylline similar to caffeine, a closely related cmpd • While this can considered be a negative side effect, it can be helpful in infants who suffer from sleep apnea
Diuretic • Increased urinary output that may be a problem for some individuals - however the effect is usually mild • May help dry excessive respiratory secretions thus help suppress coughing