Теофилин

Описание

Theophylline is a methylxanthine that acts as a weak bronchodilator. It is useful for chronic therapy and is not helpful in acute exacerbations.
Theophylline is a methylxanthine alkaloid that is a competitive inhibitor of phosphodiesterase (PDE; Ki = 100 μM). It is also a non-selective antagonist of adenosine A receptors (Ki = 14 μM for A1 and A2). Theophylline induces relaxation of feline bronchiole smooth muscle precontracted with acetylcholine (EC40 = 117 μM; EC80 = 208 μM). Formulations containing theophylline have been used in the treatment of asthma and chronic obstructive pulmonary disease (COPD).

Химические свойства

white to light yellow crystal powder

Физические свойства

Appearance: white, crystalline powder, odorless, with a bitter taste. Solubility: freely soluble in solutions of alkali hydroxides and in ammonia; sparingly soluble in alcohol, in chloroform, and in ether; slightly soluble in water. Water solubility, 7.36?g/L (20?°C); density, 1.62?g/cm3 ; melting point, 270–274?°C; boiling point, 390.1?°C (760? mmHg); flash point, 189.7?°C; vapor pressure, 2.72E-06? mmHg (25?°C).

Использование

theophylline is tonic and skin conditioning. Its cosmetic activity is not clearly or definitively established. It is most often found in anti-cellulite products. Theophylline is in the same family of bio chemicals as caffeine. It is naturally occurring in tea.

Определение

ChEBI: Theophylline is a dimethylxanthine having the two methyl groups located at positions 1 and 3. It is structurally similar to caffeine and is found in green and black tea. It has a role as a vasodilator agent, a bronchodilator agent, a muscle relaxant, an EC 3.1.4.* (phosphoric diester hydrolase) inhibitor, an anti-asthmatic drug, an anti-inflammatory agent, an immunomodulator, an adenosine receptor antagonist, a drug metabolite, a fungal metabolite and a human blood serum metabolite.

Показания

Twenty years ago theophylline (Theo-Dur, Slo-bid, Uniphyl, Theo-24) and its more soluble ethylenediamine salt, aminophylline, were the bronchodilators of choice in the United States. Although the β2-adrenoceptor agonists now fill this primary role, theophylline continues to have an important place in the therapy of asthma because it appears to have antiinflammatory as well as bronchodilator activity.

Общее описание

Odorless white crystalline powder. Odorless. Bitter taste.

Реакции воздуха и воды

Slightly soluble in water.

Профиль реактивности

Theophylline neutralizes acids in exothermic reactions to form salts plus water. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.

Опасность

Questionable carcinogen.

Пожароопасность

Flash point data for Theophylline are not available, however Theophylline is probably combustible.

Биологическая активность

Bronchodilator, anti-inflammatory and immunomodulator. Antagonizes adenosine receptors and is a weak non-selective inhibitor of phosphodiesterases (PDEs).

Механизм действия

In spite of a great deal of investigation, just how theophylline causes bronchodilation is not clearly understood. Inhibition of the enzyme PDE, which is responsible for the hydrolysis of cAMP and cyclic guanosine monophosphate (cGMP), generally is put forth as the mechanism of action; however, theophylline also is an adenosine antagonist and has been implicated in stimulation of the release of catecholamines. It has been clearly shown that theophylline does inhibit PDEs in vitro, and x-ray crystallographic studies have identified the binding residues that interact with the methylxanthines. Theophylline binds to a subpocket of the active site and appears to be sandwiched between a phenylalanine and a valine via hydrophobic bonds. Its binding affinity is reinforced by hydrogenbonding between a tyrosine and N-7 and a glutamine and O-6 of the xanthine ring system. There are more than 11 families of PDEs, and studies have shown that theophylline binds in a similar manner to both the PDE4 and PDE5 family isoforms.

Фармаколо?гия

Smooth muscle relaxation, central nervous system (CNS) excitation, and cardiac stimulation are the principal pharmacological effects observed in patients treated with theophylline.The action of theophylline on the respiratory system is easily seen in the asthmatic by the resolution of obstruction and improvement in pulmonary function. Other mechanisms that may contribute to the action of theophylline in asthma include antagonism of adenosine, inhibition of mediator release, increased sympathetic activity, alteration in immune cell function, and reduction in respiratory muscle fatigue. Theophylline also may exert an antiinflammatory effect through its ability to modulate inflammatory mediator release and immune cell function.
Inhibition of cyclic nucleotide phosphodiesterases is widely accepted as the predominant mechanism by which theophylline produces bronchodilation. Phosphodiesterases are enzymes that inactivate cAMP and cyclic guanosine monophosphate (GMP), second messengers that mediate bronchial smooth muscle relaxation.

Клиническое использование

The principal use of theophylline is in the management of asthma. It is also used to treat the reversible component of airway obstruction associated with chronic obstructive pulmonary disease and to relieve dyspnea associated with pulmonary edema that develops from congestive heart failure.

Побочные эффекты

Theophylline has a narrow therapeutic index and produces side effects that can be severe, even life threatening. Importantly, the plasma concentration of theophylline cannot be predicted reliably from the dose. In one study, the oral dosage of theophylline required to produce therapeutic plasma levels (i.e., between 10 and 20 μg/mL) varied between 400 and 3,200 mg/day. Heterogeneity among individuals in the rate at which they metabolize theophylline appears to be the principal factor responsible for the variability in plasma levels. Such conditions as heart failure, liver disease, and severe respiratory obstruction will slow the metabolism of theophylline.

Профиль безопасности

Human poison by ingestion, parenteral, intravenous, and rectal routes. Experimental poison by multiple routes. An experimental teratogen. Human systemic effects: coma, convulsions or effect on seizure threshold, cyanosis, EKG changes, fever and other metabolic effects, heart arrhythmias, heart rate change, hyperglycemia, metabolic acidosis, nausea or vomiting, potassium-level changes, respiratory stimulation, salivary gland changes, somnolence, tremor. Experimental reproductive effects. Human mutation data reported. Used as a dturetic, cardtac stimulant, smooth muscle relaxant, and to treat asthma. When heated to decomposition it emits toxic fumes of NOx.

Экологическая судьба

Theophylline is readily broken down in the environment. It may undergo photolytic degradation in the air or when exposed to light. In moist soil, or aqueous environments, it undergoes rapid biodegradation.

Метаболизм

Chemically, theophylline is 1,3-dimethylxanthine and contains both an acidic and a basic nitrogen (N-7 and N-9, respectively). Physiologically, it behaves as an acid (pKa = 8.6), and its poor aqueous solubility can be enhanced by salt formation with organic bases. Theophylline is metabolized by a combination of C-8 oxidation and N-demethylation to yield methyluric acid metabolites. The major urinary metabolite is 1,3-dimethyl uric acid, which is the product of the action of xanthine oxidase. Because none of the metabolites is uric acid itself, theophylline can be safely given to patients who suffer from gout.

Методы очистки

It crystallises from H2O as the monohydrate which becomes anhydrous above 100o. It is freely soluble in hot H2O, but its solubility at 15o is 0.44%. It complexes with heavy metals. It is a diuretic, vasodilator and a cardiac stimulant. [Lister Purines Part II, Fused Pyrimidines Brown Ed, Wiley-Interscience pp253-254 1971, ISBN 0-471-38205-1, Beilstein 26 H 455, 26 I 134, 26 II 263, 26 III/IV 2331.]

Меры предосторожности

Theophylline should be used with caution in patientswith myocardial disease, liver disease, and acutemyocardial infarction. The half-life of theophylline isprolonged in patients with congestive heart failure.Because of its narrow margin of safety, extreme cautionis warranted when coadministering drugs, such as cimetidineor zileuton, that may interfere with the metabolismof theophylline. Indeed, coadministration of zileutonwith theophylline is contraindicated. It is alsoprudent to be careful when using theophylline in patientswith a history of seizures.

использованная литература

Fischer., Ber., 30, 553 (1897)
Schwabe., Arch. Pharm., 245, 312 (1907)
Biltz, Strufe.,Annalen, 404, 137, 170(1914)
Yoshitomi., Chem. Abstr., 19,2303 (1925)
Mossini., Boll. chim. farm., 75, 557 (1936)
Deichmeister., Farm. Zhur., 13, 18 (1940)
Deichmeister., Chem. Zentr., 1, 1280 (1942)
Deniges., Bull. trav. soc. ph arm. Bordeaux, 79, 141 (1941)
Lesser., Drug & Cosmetic Ind., 66, 276,340 (1950)