Which of these symptoms is a common side effect of theophylline?

Theophylline is a medication primarily used as a bronchodilator in the management of respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). It functions by relaxing the muscles in the airways, improving airflow to the lungs. However, theophylline has a range of side effects due to its stimulating effects on the central nervous system, and one common reaction is insomnia.

Insomnia can occur as theophylline increases levels of neurotransmitters like catecholamines in the brain, which can lead to heightened alertness and difficulty sleeping. Since adequate rest is vital for managing respiratory conditions effectively, the side effect of insomnia can impact a patient's health negatively.

While palpitations, sinus tachycardia, and an increased heart rate are also potential side effects associated with theophylline due to its stimulant properties, insomnia specifically relates to its direct influence on the central nervous system and is thus a distinct outcome that can significantly affect a patient's quality of life.