There should be a chart in the med room somewhere that tells you the time frame window during which you can give certain meds early or late. However, six hours early is definitely a problem. I think I know what your issue is. When a new medication is entered, it will sometimes have it on the MAR for the first dose to be given at the time the order was entered, and then the second dose is going to be on the usual schedule, and often that can cause numerous med errors. I think it is a computer glitch that needs to be addressed. However, until they do, as the nurse, you have to start paying attention to that and it is in your best interest to know which meds should not be given. If the first dose is a stat order, it's likely never going to be an issue, otherwise, you need to be diligent.