Praise be to Allah.
The fast is broken when anything reaches the stomach, according to the majority of jurists, unless it will not remain in the stomach and will be taken back out, such as a scope, according to the view of the Hanafis, who stipulate that what enters the stomach should remain there [for the fast to be broken].
Al-Kasani said in Bada’i‘ as-Sana’i‘ (2/93): If someone is stabbed with a spear and it reaches his stomach or his brain, if it is extracted with its head, it does not invalidate the fast, but if the head remains in him, it does invalidate the fast. End quote.
It says in a statement of the Islamic Fiqh Council regarding things that do not break the fast of one who is fasting:
Gastroscopy, if it is not accompanied by introduction of fluids (solutions) or other substances."(Majallat al-Majma‘ 10/2/453-455).
With regard to this injection, which contains a solution and other substances that reach the stomach and remain there, it does break the fast.
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) said in ash-Sharh al-Mumti‘ (6/370-371): If someone has a gastroscopy and the scope enters his stomach, then by doing that he has broken his fast [that is, according to the Hanbali madhhab].
But the correct view is that it does not break the fast unless there is some oil or the like on or in this scope which reaches the stomach through the scope, in which case the fast is broken thereby, and it is not permissible to use it during an obligatory fast except in the case of necessity. End quote.
If this injection reaches the stomach, then it breaks the fast, even if it does not provide nourishment.
Based on that, it is not permissible to use it during an obligatory fast except in the case of necessity, and the one who uses it breaks his fast thereby and must make up the day on which he broke his fast.
For more information, please see the answer to question no. 250660 .
And Allah knows best.