Methylxanthines are molecular compounds that act simultaneously as cardiac stimulants, diuretics, and smooth muscle relaxants. While the most commonly known form is caffeine, certain methylxanthine compounds are used as bronchodilators to stimulate the cardiovascular and respiratory systems in patients with chronic obstructive pulmonary disease (COPD). Methylxanthine compounds are able to provide short-term relief from the effects of COPD, and can be administered immediately in the event of a respiratory episode.

For COPD patients — who have chronic obstructive lung or airway disease, emphysema, and chronic bronchitis — methylxanthine compounds act on constricted bronchi and bronchioles to improve airflow, reduce inflammation, and relax airways, while increasing blood flow via cardiac stimulation. Methylxanthines can also be used to treat asthma, and can be administered via inhalers or in tablet form. They affect the throat, lungs, heart, and other key parts of the bronchial and pulmonary systems. The accelerated pulmonary response and relaxation of the airways caused by methylxanthine compounds is why frequent coffee drinkers at times complain of shortness of breath, increased heart rate, and even mild arrhythmia.

Drugs classified as methylxanthines are actually derivatives of xanthine, which is a purine found in the human body. Methylation involves adding methyl groups to xanthines to form alkaloids. Both methylated and nonmethylated synthetic xanthines can be used as mild stimulants. Other than caffeine, other methylxanthine compounds include theophylline, aminophylline, paraxanthine, and theobromine. Theophylline and aminophylline are specifically used as bronchodilators in COPD treatment.

Methylxanthines can be artificially created or derived from substances, such as coffee, tea, cocoa, and chocolate. The effect of methylxanthine is why people suffering respiratory discomfort, colds, or allergies often self-treat by drinking tea, breathing the steam from tea, or inhaling the aroma of steeping tea leaves, all of which can help to relax airways and ease breathing. While not an effective long-term treatment for COPD or other respiratory issues, these effects can provide temporary relief from mild discomfort. Methylxanthine compounds are also approved by the International Olympic Committee (IOC), while caffeine is not. Therefore, Olympic contestants may use methylxanthines to temporarily increase energy and adrenaline response.

Patients with gastroesophageal reflux disease, or GERD, may suffer negative side effects from methylxanthines, or foods containing them — particularly high-caffeine drinks like coffee and tea — or high-theobromine foods, such as chocolate. As methylxanthine compounds relax the esophagus, they can contribute to gastric reflux reactions. While small quantities may not cause a reaction, larger intakes can lead to nausea and heartburn.