Abortive is another term for rescue medications. They are used to help stop a headache that is already present. They are most effective when taken early on in the headache. Some abortives can be bought over the counter, but the more potent and effective are usually obtained by prescription. Choice of abortive agents depends on a number of factors, including other medications you are taking, the frequency, severity and duration of your headaches, finances, and other variables. There are many options and these should be discussed with your headache doctor or health professional.