The prescription of over-the-counter (OTC) NSAIDs cannot be traced using this database,
as such drugs are not reimbursed by the Italian National Health Service. This may give rise to a
potential under-estimation of NSAID exposure concerning NSAIDs with OTC status in Italy
(e.g. ibuprofen, acetylsalicylic acid, ketoprofen lysine salt, and others). However, NSAIDs used
as OTC drugs contain much lower dosage of active ingredient as compared to prescribed
NSAIDs and the dose-effect response, which may play a role in NSAID-associated CKD
occurrence, is therefore likely to be much less significant than for prescription NSAIDs.