Shafaqna Pakistan: Islamic Laws on fasting according to the Fatwas of the Grand Ayatollah Sistani.
Things that invalidate a fast: Using injections and medical drops
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.
Spanish
El Ayuno – El uso de los medicamentos o inyyecciones para el ayunante
Reglas : Es mejor abstenerse de todo tipo de inyecciones o aplicaciones de sustancias alimenticias (suero, vitaminas, etc.), pero no hay inconveniente en aplicarse inyecciones anestésicas o medicinales
Source: Shafaqna English