Theophylline, also known as 1,3-dimethylxanthine, is a phosphodiesterase inhibiting drug used in therapy for respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma under a variety of brand names. As a member of the xanthine family, it bears structural and pharmacological similarity to theobromine and caffeine, and is readily found in nature, being present in tea (Camellia sinensis) and cocoa (Theobroma cacao). A small amount of theophylline is one of the products of caffeine metabolic processing in the liver.Acebrophylline, an airway mucoregulator and anti-inflammatory agent is a combination product of ambroxol and theophylline 7 acetic acid. Medical uses
The main actions of theophylline involve:

relaxing bronchial smooth muscle
increasing heart muscle contractility and efficiency (positive inotrope)
increasing heart rate (positive chronotropic)
increasing blood pressure
increasing renal blood flow
anti-inflammatory effects
central nervous system stimulatory effect mainly on the medullary respiratory center.The main therapeutic uses of theophylline are aimed at:

chronic obstructive pulmonary disease (COPD)
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. Uses under investigation
A clinical study reported in 2008 that theophylline was helpful in improving the sense of smell in study subjects with anosmia.In 2004, a small clinical study compared theophylline to methylphenidate for the treatment of attention-deficit hyperactivity disorder in children and adolescents. 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).
It has recently been shown that the oxidative stress associated with cigarette smoke can inhibit the activity of HDAC2, thereby blocking the anti-inflammatory effects of corticosteroids.) Pharmacokinetics
Absorption
When theophylline is administered intravenously, bioavailability is 100%. Distribution
Theophylline is distributed in the extracellular fluid, in the placenta, in the mothers milk and in the central nervous system. The volume of distribution is 0.5 L/kg. The protein binding is 40%. The volume of distribution may increase in neonates and those suffering from cirrhosis or malnutrition, whereas the volume of distribution may decrease in those who are obese. Metabolism
Theophylline is metabolized extensively in the liver (up to 70%). It undergoes N-demethylation via cytochrome P450 1A2. It is metabolized by parallel first order and Michaelis-Menten pathways. Metabolism may become saturated (non-linear), even within the therapeutic range. Small dose increases may result in disproportionately large increases in serum concentration. Methylation to caffeine is also important in the infant population. Smokers and people with hepatic (liver) impairment metabolize it differently. Both THC and nicotine have been shown to increase the rate of theophylline metabolism. 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.