Drug doseages. Probably nothing if its just one dose. You will not get the benefit of the drug [or any drug for that matter] if you do not take it as prescribed regularly. You see, the way the body metabolizes or breaks down a drug is different for each particular medicine which is why some are once a day and others 4 times a day. You need a certain blood level of the drug for it to work right.
Nothing. In many studies it has been seen that patients would forget a dose of daily medicine and no major disadvantages were noted. This does not mean that you can miss adobe every other day.