2. introduces drugs into muscle or directly into the bloodstream.

Intravenous injection.

Explanation:

Injections are the needle used for the transfer of chemicals or drugs from outside environment directly in to the body of an individual. Different body regions are used to inject different drugs depending on their function and mode of action.

Intravenous injections are the needles used to inject the drug directly into the blood stream in the veins and in the muscles. This intravenous injection prevents the over dosage of drugs and proves quite effective in its function.

Thus, the answer is intravenous injection.