Theophylline

thumb|right|upright|Theophylline extended-release tablets in Japan

Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other methylxanthine drugs (e.g., theobromine and caffeine).

Medical uses

The main actions of theophylline involve:

The main therapeutic uses of theophylline are for treating:

Asthma
Infant apnea
Blocks the action of adenosine; an inhibitory neurotransmitter that induces sleep, contracts the smooth muscles and relaxes the cardiac muscle.
Treatment of post-dural puncture headache.

Performance enhancement in sports

Theophylline and other methylxanthines are often used for their performance-enhancing effects in sports, as these drugs increase alertness, bronchodilation, and increase the rate and force of heart contraction. There is conflicting information about the value of theophylline and other methylxanthines as prophylaxis against exercise-induced asthma.

Adverse effects

The use of theophylline is complicated by its interaction with various drugs and by the fact that it has a narrow therapeutic window (<20 mcg/mL). Seizures can also occur in severe cases of toxicity, and are considered to be a neurological emergency. Theophylline toxicity can be treated with beta blockers. In addition to seizures, tachyarrhythmias are a major concern. Theophylline should not be used in combination with the SSRI fluvoxamine.

Pharmacology

Pharmacodynamics

Like other methylated xanthine derivatives, theophylline is a competitive nonselective phosphodiesterase inhibitor which increases intracellular levels of cAMP and cGMP, activates PKA, inhibits TNF-alpha and inhibits leukotriene synthesis, and reduces inflammation and innate immunity. Theophylline activates histone deacetylases.

Excretion

Theophylline is excreted unchanged in the urine (up to 10%). Clearance of the drug is increased in children (age 1 to 12), teenagers (12 to 16), adult smokers, elderly smokers, as well as in cystic fibrosis, and hyperthyroidism. Clearance of the drug is decreased in these conditions: elderly, acute congestive heart failure, cirrhosis, hypothyroidism and febrile viral illnesses.

Proton NMR

The characteristic signals, distinguishing theophylline from related methylxanthines, are approximately 3.23δ and 3.41δ, corresponding to the unique methylation possessed by theophylline. The remaining proton signal, at 8.01δ, corresponds to the proton on the imidazole ring, not transferred between the nitrogen. The transferred proton between the nitrogen is a variable proton and only exhibits a signal under certain conditions.

<sup>13</sup>C-NMR

The unique methylation of theophylline corresponds to the following signals: 27.7δ and 29.9δ. The remaining signals correspond to carbons characteristic of the xanthine backbone.

Natural occurrences

Theophylline is naturally found in cocoa beans. Amounts as high as 3.7 mg/g have been reported in Criollo cocoa beans.

Trace amounts of theophylline are also found in brewed tea, although brewed tea provides only about 1 mg/L, which is significantly less than a therapeutic dose.

Trace amounts of theophylline are also found in guarana (Paullinia cupana) and in kola nuts.

Crystalline forms in solid state

It has been shown, that Theophylline has five polymorphic forms. In all these crystalline materials hydrogen bonds play an important role.

History

Theophylline was first extracted from tea leaves and chemically identified around 1888 by the German biologist Albrecht Kossel. Seven years later, a chemical synthesis starting with 1,3-dimethyluric acid was described by Emil Fischer and Lorenz Ach. The Traube purine synthesis, an alternative method to synthesize theophylline, was introduced in 1900 by another German scientist, Wilhelm Traube. Theophylline's first clinical use came in 1902 as a diuretic. It took an additional 20 years until it was first reported as an asthma treatment. The drug was prescribed in a syrup up to the 1970s as Theostat 20 and Theostat 80, and by the early 1980s in a tablet form called Quibron.

Etymology

The name 'theophylline' derives from "Thea"—the former genus name for tea + Ancient Greek φύλλον (phúllon, "leaf") + -ine.