Does placing a substance in the nose during a medical examination of the larynx invalidate the fast, given that one does not feel it reaching the throat, and is this considered a necessity?

A sick person is permitted to break their fast in Ramadan (definition) if fasting becomes difficult for them or if they fear an increase in their illness. The questioner's fast is valid as long as she did not taste the medicine in her throat when instilling drops in her nose. However, if she did taste it, then she must make up the fast (qada') and not offer expiation (kaffarah (definition)). Consuming anything that breaks the fast without a great necessity is considered a major sin and invalidates the fast, but it does not necessitate expiation according to the most authoritative opinion. And whoever is compelled to break their fast commits no sin, but they must make up the fast.