How is your your fish doing today? I was also looking about the ingredients of the med you are using, but I couldn't find anything. Fish meds can be not only expensive, but also hard to find in some countries. I also had this problem, my fish were ill and I couldn't have enough time to buy the meds online, so being desperate I simply went to drugstore (for people) and I ask for one tab of med, telling them I needed for my fish tank. I didn't have prescription, but they were very nice and gave me. And it was a lot more cheaper too. But not all meds can be found this way. For example, I was looking to buy Kanaplex (Kanamycin). First, I went to a lot of pet stores but it wasn't available anywhere, then I when to a drugstore for people where tabs were not available either, so in the end I went to a drugstore for animals were I found it. Anyway, you have to be very careful with the dosage this way and calculate it exactly for the amount of water that you have in your tank. I was calculating it twice or even more in order to be 100% sure it was right dosage.
I think that one of the biggest problem that people have when their fish become ill is the fact that they are not prepared. So it would be very good to have at home a few most useful meds (1 tab of each is enough) for this kind of unpredictable and sad events. It will save you a lot of time.
Don't forget about the water changes. For a 2.5 liters QT you need frequent water changes. Callistra explained very well about how to do them.
Did your fish poop in the end? If yes, how did it look like?
I didn't suggested Maracyn (Erytromycin) which is good on some gram-positive bacteria but Maracyn II (Minocycline). Anyway, there are many different approaches on dropsy, some of them suggest to use Kanaplex, while some others suggest Maracyn II, I think they are both right in some ways. Whether the med used will be successful for all cases will depend on the cause, not all cases are bacterial.