A nurse entering a patient's allergies into the designated computer field used the abbreviation "PCN" to indicate penicillin. The pharmacy computer interpreted the abbreviation to mean PCN-200, a supplement that contains grapefruit seed extract, and consequently screened the patient's ordered drugs for the presence of grapefruit seed extract, not penicillin. The pharmacy staff, unaware of PCN-200 ingredients, assumed that the computer was screening orders for penicillin allergies. Fortunately, no adverse events were reported before the problem was uncovered.
Abbreviating drug names can confuse people and computers, so completely spell out drug names in all your communications.