Which of the following is NOT a side effect of theophylline?

Theophylline is a bronchodilator commonly used in the treatment of respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD). Its side effects are typically related to its stimulant properties on the central nervous system and gastrointestinal tract. Common side effects associated with theophylline include headache, nervousness, and seizures, which can occur due to increased central nervous system stimulation and its metabolic effects.

Constipation, however, is not widely recognized as a typical side effect of theophylline. The drug does not generally exert an effect that would lead to constipation, unlike some other medications that might slow gastrointestinal motility. In fact, theophylline can sometimes stimulate gastrointestinal activity, possibly leading to symptoms such as nausea or abdominal discomfort rather than constipation.

Therefore, identifying constipation as the correct answer highlights the understanding that while theophylline has several well-documented side effects, it does not commonly cause constipation, making this choice accurate in the context of the question.