If your medication is a benefit drug, not on the formulary, and your vacation or travels fall on your due date to repeat your prescription then yes! Just ask your pharmacist and you will be able to get up to an extra month of refills.
First, double check the remaining amount of medication you have left .Compare this with your prescribed dosage and how long you've been on this regimen to verify that you have in fact missed a dose. If this is the case, immediately take your prescribed dosage and continue as usual. It's best to avoid "doubling up” to compensate for missed medications. This could result in an overdose.
A bevy of reasons, there could be a batch recall or the shipment itself might be spoiled. The manufacturers may be unable to get the ingredients. The drug may be high in demand and not able to meet supply needs or a manufacturer might be waiting to accumulate a large enough order on this item(s) to match profit with production/shipping costs. There could also be a cost issue causing friction with obtaining the drug from the manufacturer as well. In any case, talk to your doctor! Do not delay; there are usually other options that can be utilized.