What is a common effect of theophylline after administration?

Theophylline is a medication commonly used as a bronchodilator for conditions such as asthma and chronic obstructive pulmonary disease (COPD). One of the well-known side effects of theophylline is tachycardia, which is an increased heart rate. This occurs because theophylline acts as a central nervous system stimulant and can increase catecholamine levels, leading to enhanced heart rate and contractility.

Additionally, theophylline's ability to relax bronchial smooth muscle and improve airflow can indirectly lead to more vigorous physical activity and a feeling of increased energy; however, tachycardia is a more direct and commonly noted effect immediately following administration. It is also important to monitor the patient's heart rate as excessive tachycardia can lead to more serious cardiovascular effects, making this side effect particularly relevant in clinical context.

In contrast, while weight loss and severe headaches can occur, they are not universally common effects of theophylline. Weight loss may happen due to its metabolic effects but is not a primary symptom associated with its acute use. Severe headaches can be a side effect but tend to be less frequent and often related to toxicity or high serum levels rather than standard treatment.