As we all know, being interrupted during a task greatly increases the chance we’ll go off-kilter (I discuss the worst circumstances and how you can minimize the risk of mistakes in my book Planning to remember). Medication errors occur as often as once per patient per day in some settings, and around one-third of harmful medication errors are thought to occur during medication administration. Now an in-depth study involving 98 nurses at two Australian teaching hospitals over 505 hours has revealed that at least one procedural failure occurred in 74.4% of administrations and at least one clinical failure in 25%. Each interruption was associated with a 12.1% increase in procedural failures and a 12.7% increase in clinical errors. Procedural failures include such errors as failure to check patient's identification, record medication administration, use aseptic technique; clinical failures such errors as wrong drug, dose, or route. Interruptions occurred in over half of the 4000 drug administrations. While most errors were rated as clinically insignificant, 2.7% were considered to be major errors — and these were much more likely to occur after interruptions, particularly after repeated interruptions. The risk of major error was 2.3% when there was no interruption; this rose to 4.7% with four interruptions. Nurse experience provided no protection against making a clinical error and was associated with higher procedural failure rates (this is common with procedural failures — expertise renders you more vulnerable, not less).
Interruptions associated with medication errors by nurses
 Association of Interruptions With an Increased Risk and Severity of Medication Administration Errors. Arch Intern Med. 170(8), 683 - 690.(2010).