Changing from lasix IV to oral is usually done when the patient improves and is about to be discharged.

So shifting to oral is usually for convenience reasons.

Cardiologist usually shifts the patient to the same dose orally and monitor for a day or two before discharge.

You should know that the bioavailability of the oral lasix is about 50%, meaning the same dose orally will have 50% of the efficacy of the IV.

Regarding the stability, it will be changing according to the preparation. If you crush the tablet and use it as crushed or added to suitable oral liquid, any remaining portion must be discarded.

You should know that Furosemide is practically insoluble in water