Concept:
The route of drug administration is selected according to the condition of the patient and the urgency of treatment.
Step 1: An unconscious patient cannot swallow tablets or liquids safely.
Step 2: Oral route may cause choking or aspiration in such patients.
Step 3: Sublingual route also requires patient cooperation.
Step 4: Parenteral route means administration by injection, such as intravenous, intramuscular, or subcutaneous route.
Step 5: Parenteral route is suitable for unconscious patients because it does not require swallowing.
\[
\boxed{\text{Parenteral}}
\]