A drug given by a parenteral route acts outside which tract?

A drug administered via a parenteral route bypasses the gastrointestinal tract entirely. Parenteral routes include administration methods such as intravenous, intramuscular, or subcutaneous injections, which deliver the medication directly into the body, avoiding the complexities of digestion and absorption that occur in the gastrointestinal tract. This allows for rapid onset of action and more precise control of drug levels in the bloodstream.

The other options relate to systems or structures that are not directly involved in the absorption of parenterally administered drugs. The respiratory tract is related to inhaled medications, the circulatory tract pertains to the movement of blood in the body, and the neurological tract involves the nervous system, which is not the primary pathway for drug action in this context. Therefore, the correct answer highlights the specific bypassing of the gastrointestinal tract when drugs are given parenterally.