Certain medications, such as scheduled drugs, can only be prescribed on a month-by-month basis for exactly 30 pills. You have to get a new script every month.
Next, you have to be lucky enough that your pharmacy has your medicine and specific dosage in stock. If not, it can take several days for a new order to arrive, and other times, it might take more than a week. If you’re out of medicine, and nothing is available nearby, you’re out of luck.
In the exception of either not taking your meds on certain days or intentionally taking less than your prescribed dose–and both of these scenarios can potentially leave you unable to function–there is no other way to create an emergency stash.
I’m not your guy, pal.