Which route can bypass first-pass effect to improve bioavailability?

Which route can bypass first-pass effect to improve bioavailability?

• A. Sublingual or transdermal
• B. Oral
• C. Intramuscular
• D. Intravenous

Answer: (A)

The main idea is bypassing hepatic first-pass metabolism. When a drug is taken orally, it is absorbed from the gut and carried via the portal vein to the liver, where a portion can be metabolized before reaching systemic circulation. Routes that deliver the drug directly into the systemic bloodstream avoid this first-pass step, improving bioavailability. Sublingual administration places the drug under the tongue, where it gets absorbed through the rich capillary network into the venous blood that drains into the systemic circulation. This means the drug reaches the bloodstream without passing through the liver first, so more of the active drug remains intact. Transdermal delivery lets the drug pass through the skin into dermal capillaries and then into systemic circulation, again bypassing the liver on the first pass. This is especially useful for providing steady, sustained levels and for drugs that are poorly tolerated orally due to first-pass metabolism. While other routes like intramuscular or intravenous also bypass first-pass metabolism, the question highlights non-oral, direct-to-systemic routes that are commonly used specifically to avoid first-pass effects, with sublingual and transdermal being the classic examples. This is why those routes are the best answer.

The main idea is bypassing hepatic first-pass metabolism. When a drug is taken orally, it is absorbed from the gut and carried via the portal vein to the liver, where a portion can be metabolized before reaching systemic circulation. Routes that deliver the drug directly into the systemic bloodstream avoid this first-pass step, improving bioavailability.

Sublingual administration places the drug under the tongue, where it gets absorbed through the rich capillary network into the venous blood that drains into the systemic circulation. This means the drug reaches the bloodstream without passing through the liver first, so more of the active drug remains intact.

Transdermal delivery lets the drug pass through the skin into dermal capillaries and then into systemic circulation, again bypassing the liver on the first pass. This is especially useful for providing steady, sustained levels and for drugs that are poorly tolerated orally due to first-pass metabolism.

While other routes like intramuscular or intravenous also bypass first-pass metabolism, the question highlights non-oral, direct-to-systemic routes that are commonly used specifically to avoid first-pass effects, with sublingual and transdermal being the classic examples. This is why those routes are the best answer.