Some patients develop side effects from theophylline even at low serum concentrations. We designed a prospective study to evaluate the side effects of theophylline.

A Prospective, controlled trial study was conducted. The low-dose group received an intravenous continuous aminophylline dose of 5 mg/kg/day on the first day and subsequently 10 mg/kg/day on the following two days. The usual-dose group received 10 mg/kg/day for three days and the control group received normal saline for three days. Heart rate, respiratory rate, serum concentration of theophylline, and four adverse events (irritability, sleep disturbance, jitter, and vomiting) were checked at the time of admission and at 2, 12, 24, 48, and 72 h after the start of aminophylline infusions.

Nine patients out of 37 in the low-dose group and six of 21 in the usual-dose group dropped out because of uncontrolled irritability. The serum concentrations of theophylline in dropouts (3.68±1.93 ìg/mL) and participants (4.47±2.45 ìg/mL) were not significantly different. Irritability was a more frequent side effect in the usual-dose group at 12 h, but there was no difference between the low-dose and usual-dose groups in terms of vomiting, sleep disturbance, and jitter. Most of the severe adverse effects were observed in children below two years of age.

Some patients dropped out regardless of the initiating aminophylline dose, especially patients under the age of two years.