Pisa syndrome due to donepezil: pharmacokinetic interactions to blame?

We report a case of Pisa syndrome (PS) due to the acetylcholinesterase inhibitor donepezil which may have been precipitated by pharmacokinetic interactions with commonly used medications. PS is defined as a reversible lateral bending of the trunk with a tendency to lean to one side. This is a rare but very distressing complication with this commonly used medication which was not initially recognised, leading to increasing disability for the patient and significant carer stress. Cessation of donepezil and modulation of potential interacting medications resulted in complete resolution. [ABSTRACT FROM AUTHOR]