Which of the following is the fastest and most efficient route of administration?

• A. A IV injection
• B. B Smoking
• C. C Oral administration
• D. D Intra-muscular administration

Answer: (B)

Speed and efficiency of drug delivery depend on how directly the drug reaches the bloodstream. Delivering a drug straight into a vein provides the highest bioavailability—essentially all of the dose enters the circulation immediately—leading to an almost instantaneous and predictable effect. That makes intravenous administration the fastest and most reliable way to achieve a systemic effect.

Inhalation or smoking can bring a drug into the bloodstream very quickly because the lungs offer a large surface area for rapid absorption, but the exact amount that reaches circulation can vary with how deeply you inhale, how long you hold your breath, and the drug’s properties. This variability makes it less predictable and often less efficient for delivering a precise dose, even though the onset may be rapid.

Oral administration must pass through the digestive system and undergo first-pass metabolism in the liver. This process slows absorption and reduces the amount reaching systemic circulation, resulting in slower and more variable effects.

Intramuscular administration lies between IV and oral in speed and consistency; absorption depends on blood flow to the muscle and other factors, so onset is slower than IV and more variable.

So, the fastest and most efficient route for delivering a drug systemically is intravenous injection.