In 2011, the FDA published guidelines regarding the prescribing of citalopram and escitalopram following publication of evidence showing prolongation of the QT period at therapeutic doses. This paper looked at the impact of these guidelines on the prescribing practices of clinicians in one centre. It showed that clinicians have changed practices in accordance with the guidelines for citalopram but no clear patterns were seen in escitalopram or when looking individually at thespecific guidelines for patients over 60 years of age. There was no evidence of increased concordance by clinicians with the guidelines in patients taking other QT prolonging drugs who are at additional risk. Overall, the guidelines have made an impact on practice but this is partial and2% of all patients still remain on regimes that do not fit the guidelines. The possible reasons for this are explored.