Which route of administration would be employed for immediate effects on the body?

The chosen route of administration is inhalation, which is known for delivering substances directly to the lungs, allowing for rapid absorption into the bloodstream. This method is particularly effective because the alveolar surface area is vast, enabling quick transfer of medications into the circulation. As a result, inhalation is often used in emergency situations, such as delivering bronchodilators for asthma attacks or anesthetics in surgical settings, where immediate physiological responses are critical.

While other routes like intramuscular can also provide relatively quick effects, the onset of action is generally slower compared to inhalation. Oral administration typically requires the substance to undergo digestion and absorption in the gastrointestinal tract, which delays its effects. Rectal administration can provide relatively quick absorption, particularly in cases of nausea or when a patient cannot take oral medications, but it does not match the speed of inhalation. Thus, inhalation emerges as the most effective route for immediate effects on the body.