Good question. Pseudoephedrine belongs to a group of medicines that act as decongestants by constricting small blood vessels in the nasal passages. Thus, less inflammation and congestion as the sinus tissue settles down a bit. It may improve thinking by improving breathing and sleep. Sinus problems are associated with sleep disorders, particularly obstructive sleep apnea. When using pseudoephedrine you may be sleeping more soundly at night and that is directly associated with improved thinking and memory.

There are many others, though, who find the nervousness caused by pseudoephedrine causes them to lose sleep resulting in a ‘foggy brain'. I would suggest looking at your sinus condition in greater detail and assuring good sleep to improve brain health now and in the future.