FPGEE 2025 Practice Exam for NABP – The Complete All-in-One Guide to Exam Success!

First-pass metabolism refers to the process where the concentration of a drug is significantly reduced before it reaches systemic circulation. This phenomenon is primarily associated with orally administered drugs, where the liver metabolizes a substantial amount of the drug after absorption from the gastrointestinal tract.

For drugs administered via injection routes, such as intravenous (IV), intramuscular (IM), or subcutaneous (SC), first-pass metabolism does not occur in the same way as it does with oral drugs. When a drug is injected directly into the bloodstream, it bypasses the gastrointestinal tract and the liver's first-pass effect. This means that the drug enters systemic circulation without being metabolized by the liver initially.

Each of the other options plays a role in the body’s pharmacokinetics or pharmacodynamics but does not refer to where first-pass metabolism specifically occurs for injected drugs. The stomach is involved in digestion and absorption for oral drugs but is not relevant for injections. The lungs are involved in the administration and absorption of inhaled drugs, and while the heart plays a crucial role in circulating blood, it does not metabolize drugs.

Thus, for injected drugs, the concept of first-pass metabolism is minimized or non-existent, which is why the correct answer does not align with the provided answer of