Which of the following methods is NOT a route of administration for substances?

Transcutaneous is not commonly recognized as a standard route of administration for substances. In the context of pharmacology and substance use, the main routes through which substances are administered include oral, inhalation, and injection.

Oral administration involves taking substances by mouth, where they are absorbed through the digestive system. Inhalation permits rapid onset by delivering substances directly into the lungs, where they quickly enter the bloodstream. Injection involves delivering a substance directly into the body using a needle, allowing for fast and effective absorption.

In contrast, transcutaneous typically refers to a method that is more associated with the application of medications in a patch form, which slowly releases the drug through the skin into the bloodstream over time. While it is a valid method for certain medications, in the context of this particular question regarding substances in the sphere of chemical dependency, it is not recognized as a standard primary route of administration. Therefore, it does not fit with the other routes listed.