Participants' written informed consent in low-risk pragmatic clinical trials with medicines.

: An important gap within modern medicine is the lack of enough comparative effectiveness research of marketed medicines. Low-risk pragmatic randomized controlled trials (pRCTs) are those conducted resembling usual clinical practice that poses no or minimal incremental risk compared with normal clinical practice.: This review addresses one important hurdle in the conduct of low-risk pRCTs: the need to seek participants' written informed consent.: The CIOMS ethical guidelines consider that any research that (a) would not be feasible or practicable to carry out without the waiver or modification, (b) has important social value, and (c) poses no more than minimal risks to participants, and that is approved by the relevant research ethics committee, could be conducted without participants' consent. It is clear that these provisions are applicable to some low-risk RCTs. Recently a research on the EU-CTR registry showed that only 2% of all ongoing phase 4 RCTs could have fulfilled the CIOMS provisions following the investigators' assessment. The EU clinical trial regulation - and that of other jurisdictions - should be debated on the suitableness of the conduct with an alteration or waiver of participants' consent of those low-risk pRCTs that fulfill the three CIOMS provisions.