For Paliperidone Palmitate administered monthly, when does plasma concentration start and how long does it last?

For Paliperidone Palmitate administered monthly, when does plasma concentration start and how long does it last?

• A. begins day 7 and lasts 6 months
• B. begins day 14 and lasts 12 months
• C. begins day 1 and lasts 18 months
• D. begins day 1 and lasts 18+ months

Answer: (D)

Paliperidone palmitate is a long-acting injectable that forms a subcutaneous depot and is slowly released and converted to active paliperidone. Because of this depot mechanism, detectable plasma levels appear very soon after injection—essentially by the first day. The same slow release means those drug levels persist for a very long time, so exposure can extend to around 18 months or more after the last dose. This pharmacokinetic profile explains why monthly injections maintain ongoing drug levels yet leave detectable drug for many months after cessation. So the plasma concentration begins on day 1 and lasts 18+ months.

Paliperidone palmitate is a long-acting injectable that forms a subcutaneous depot and is slowly released and converted to active paliperidone. Because of this depot mechanism, detectable plasma levels appear very soon after injection—essentially by the first day. The same slow release means those drug levels persist for a very long time, so exposure can extend to around 18 months or more after the last dose. This pharmacokinetic profile explains why monthly injections maintain ongoing drug levels yet leave detectable drug for many months after cessation. So the plasma concentration begins on day 1 and lasts 18+ months.