Every year there literally are hundreds of millions of prescriptions filled. Given the staggerring number of prescriptions that are written and filled, even a miniscule number of errors in filling the prescriptions can result in hundreds of thousands of mis-filled prescriptions. While often the consequences of an error are relatively benign – you miss a few days of getting the prescription that you need, or you experience some negative, but non-life threatening side effects, sometimes the error can result in death or permenent injury.
A number of years ago, I represented a woman who was taking a high blood pressure medication. She got pregnant and immediately, her doctor changed her medication to prevent harm to her fetus because the medication she had been on was known to retard fetal development. For several months into her pregnancy, she took the "new" medication and did fine. However, on one Sunday afternon, she went to the pharmacy and the clerk told her (their story) that two prescriptions for high blood pressure showed up, the old one and the new one and that he showed her the pills and she picked the wrong one (the old one). She took the wrong pill, the one that her doctor had discontinued when he found out she was pregnant. Not surprisingly, she developed troubles with her pregnancy and her son was born with kidneys that functioned at about 15% and which were rapidly failing. He will require a kidney replacement by the time he is 5 and he will face a life time of health related obstacles, including future kidney replacements (since replacement kidneys only have about a 15 year life span), dialysis treatments in between replacements, anti-rejection drugs, a significantly decreased life span etc.
Despite the fact that tragic results can occur from a mis-filled prescription, many pharmacies are very lax in enforcing protocols and redundant checks to ensure that prescriptions are correctly filled. Many times there are low paid and poorly trained workers in the pharmacy that are involved in filling prescriptions. Given the demands on pharmicists to increase volume (and thus profit), it is not surprising that tragic mistakes often are made.