This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
True about proton-pump inhibitor omeprazole is 
Select and explain. 
A. Not bind to plasma protein, B. CYP2C19 predicts efficacy, C. Oral bioavailability is 80%, D. All of the above
B: CYP2C19 predicts efficacy
Answer: B: CYP2C19 predicts efficacy 
Explanation: CYP 2C19 is the principal enzyme that metabolizes omeprazole to an inactive metabolite. The efficacy of drug-influenced by the CYP 2C19 genotype. 


 Reduced CYP2C19 enzyme activity (poor metabolizers) may lead to higher exposure to the drug and improve outcome at standard doses.
 In contrast, increased CYP2C19 activity (ultrarapid metabolizers) may have an insufficient response to treatment as the drug is inactivated faster.


 Omeprazole is highly plasma protein bound drug,
 It has oral bioavailability around 50%