Paliperidone Palmitate (monthly) has a plasma concentration that starts on day 1 and lasts for how long?

• A. 6 months
• B. 12 months
• C. 18+ months
• D. 24 months

Answer: (C)

The key idea is that a long-acting injectable like paliperidone palmitate forms a depot that slowly releases the active drug over an extended period. After the recommended initiation schedule (loading doses on day 1 and day 8), paliperidone palmitate starts providing detectable plasma levels from day 1, and because the depot dissolves and is slowly converted to paliperidone, those levels persist long after the injections. This slow release and tail of exposure mean plasma concentrations can remain measurable for a very long time—typically at least 18 months, hence the “18+ months” duration. The other durations (6, 12, or 24 months) don’t capture the known extended tail of exposure with this formulation.