Medication errors are defined as any preventable events that may cause or lead to inappropriate medication use or patient harm while the medication is in the control of the health care professional, patient or consumer. Such events may be related to professional practice, health care products, procedures and systems, including prescribing, order communication, product labeling, packaging and nomenclature, compounding, dispensing, distribution, administration, education, monitoring and use. A medication error can ultimately result in an adverse drug reaction (medication error with an ADR) or may have no clinical consequences (medication error without an ADR). A medication error can also be intercepted prior to the patient's exposure to the error. A potential medication error is a scenario which does not involve an actual patient, and represents circumstances or information capable of leading to the occurrence of a medication error. Medication errors cause a large number of ADRs annually: create a major public-health burden representing 18.7-56% of all adverse drug events among hospital patients; may cause unintended harm; are considered preventable. Medication errors result from a variety of human (e.g., healthcare professional; care giver; patient) and product-related reasons, for example: miscommunication of drug orders due to poor handwriting; confusion between drugs with similar names; poor packaging design; confusion of dosing units; unclear instructions. Medication errors can have an impact on: patients; healthcare professionals; pharmaceutical manufacturers; regulatory agencies; health insurance providers; national patient safety organisations.