Expert opinion considers use of theophylline to be acceptable during breastfeeding.[1,2] Maternal theophylline use may occasionally cause stimulation and irritability and fretful sleep in infants. Newborn and especially preterm infants are most likely to be affected because of their slow elimination and low serum protein binding of theophylline. There is no need to avoid theophylline products; however, keep maternal serum concentrations in the lower part of the therapeutic range and monitor the infant for signs of theophylline side effects. Infant serum theophylline concentrations can help to determine if signs of agitation are due to theophylline. Avoiding breastfeeding for 2 hours after intravenous or 4 hours after an immediate-release oral theophylline product can decrease the dose received by the breastfed infant. When theophylline is given as an oral sustained-release product, timing of nursing with respect to the dose is of little or no benefit.