When switching from oral Olanzapine, the maximum plasma concentration is reached after how many days?

• A. 7 days
• B. 13 days
• C. 21 days
• D. 28 days

Answer: (B)

Switching to a long-acting injectable olanzapine introduces a depot of drug that is released gradually over time. Because of this slow release, plasma levels rise slowly and take time to reach their highest point. For olanzapine pamoate, the average time to peak concentration is around 13 days after administration, with some variability depending on factors like the injection site. This delayed peak is why oral olanzapine is often continued for a short overlap period—to ensure consistent exposure until the depot reaches its maximum levels. Among the given options, about 13 days best reflects the typical time to reach maximum plasma concentration.