If a person has pain in his tooth, then a Dentist cleans, fills or removes it, does it affect his fasting? Does an anesthetic injection invalidate fasting?.
The things mentioned in the question do not have any effect on the validity of the fast, rather they are forgiven, but he should be careful to avoid swallowing any medicine or blood. Similarly the injection mentioned does not have any effect on the validity of the fast, because it is not like food or drink, and the basic principle is that the fast remains valid. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him)