Which medication is administered by injection rather than orally?

Adrenaline is a medication that is typically administered by injection because it provides rapid action when used in emergency situations, such as anaphylaxis or severe asthma attacks. The injectable form allows the medication to enter the bloodstream quickly, facilitating a swift response to the body's needs in critical situations.

In contrast, the other options are usually taken orally: Aspirin can be administered in pill form for pain relief and inflammation; Glucogel is a glucose gel often used for treating hypoglycemia, typically consumed rather than injected; and Glyceryl trinitrate, while there are forms that can be used sublingually (under the tongue), it is not typically injected. Therefore, Adrenaline's method of administration via injection is essential for its intended purpose in emergency medical care.