One clue to spotting a drug with enterohepatic circulation is that its effect can last longer than its blood level alone would suggest, because the drug keeps getting recycled back into circulation from the gut.
- Ibuprofen: Its liver made glucuronide conjugate is excreted in bile, reaches the intestine, and gut bacteria convert some of it back into active ibuprofen, which is reabsorbed into the blood. This repeated reabsorption is exactly what enterohepatic circulation means, and it can extend the drug's presence in the body beyond a single pass through the liver.
- Aspirin: This is hydrolysed rapidly to salicylic acid and eliminated mainly by the kidneys, without this bile recycling step.
- Piroxicam: Its long half-life comes from slow metabolism and tight protein binding, not from being recycled through bile and gut.
- Phenylbutazone: This drug is remembered more for toxicity than for any bile recycling pharmacokinetic pattern.
Because ibuprofen's conjugated form is released in bile and reabsorbed after conversion back to active drug in the gut, it is the NSAID that shows enterohepatic circulation.
Therefore, the correct answer is Ibuprofen.