Which two drugs induce GGT?

• A. Phenytoin and phenobarbital
• B. Acetaminophen and ibuprofen
• C. Prednisone and amoxicillin
• D. Erythromycin and rifampin

Answer: (A)

GGT elevation due to drug exposure most often reflects hepatic enzyme induction. Some medications ramp up the liver’s drug‑metabolizing machinery, increasing the production of many enzymes, including gamma‑glutamyl transferase. Phenytoin and phenobarbital are classic hepatic enzyme inducers; they activate nuclear receptors (like CAR and PXR) that boost transcription of several liver enzymes, leading to higher circulating GGT levels. That’s why these two drugs are the best answer: they’re well known for inducing GGT through upregulation of hepatic enzyme synthesis.

The other options don’t fit as cleanly. Acetaminophen and ibuprofen don’t act as strong inducers of GGT. Prednisone with amoxicillin isn’t a pair typically associated with GGT induction. Erythromycin can affect liver enzymes in other ways, and rifampin is an inducer, but the combination given doesn’t align as directly with GGT induction as phenytoin and phenobarbital do.