It’s allowed

Ruling 1555. Injections and intravenous drips do not invalidate a fast even if the former is an energy injection and the latter a glucose-saline drip. Similarly, a spray that is used for asthma does not invalidate a fast provided that the medicine only enters the lungs. Applying medicine [such as drops] to the eyes and ears does not invalidate a fast either, even if its taste reaches the throat. Likewise, if medicine is applied in the nose, it does not invalidate a fast as long as it does not reach the throat.

https://www.sistani.org/english/book/48/2263/