Which is NOT a common route of drug administration?

The correct choice identifies "Conversion" as not a common route of drug administration. In pharmacology, the term "route of administration" refers to the path by which a drug is delivered to the body, and it includes methods such as oral, intravenous, and transdermal.

Oral administration involves taking medication by mouth, allowing it to be absorbed through the digestive system. Intravenous administration delivers the drug directly into the bloodstream, providing immediate effects. Transdermal administration involves applying a drug through the skin, where it can be absorbed into the bloodstream over time.

"Conversion," on the other hand, does not describe a method of administering medication but rather may refer to processes like converting a medication from one form to another or changing dosing calculations. Therefore, it does not qualify as a standard route for the intake or delivery of drugs within clinical practices.