There are no contraindications to replacing packs of 63 tablets with packs of 21 tablets.

During a single sale, you can buy as many packages of the drug as are sufficient for a maximum of 120 days of using the preparation. If the doctor has recommended 1 tablet 1 time on the e-prescription and has not taken into account the dose break, it is possible to buy 5 packages of 21 tablets (or 1 pack of 63 tablets and 2 packs of 21 tablets) at a time. According to the applicable regulations on e-prescriptions, subsequent packages of the drug can be purchased no earlier than after 3/4 of the time for which the preparation has been dispensed (in this case, after 80 days). It is possible to buy a larger amount of the drug in the case of prescriptions with a longer (than the standard 30 days) validity period. In the case of a paper prescription, you can only buy 5 packs of 21 tablets.

I encourage you to contact the pharmacy of your choice, where the person filling the prescription will inform you about the configuration and when you can dispense individual packages of the drug.

We wrote about how to fill an e-prescription in a pharmacy in the article:

https://www.gdziepolek.pl/blog/jak-zrealizowac-e-recepte-w-aptece