Chewable tablets and capsules for phenytoin are not bioequivalent.

• A. Are bioequivalent
• B. Are not bioequivalent
• C. Have identical pharmacokinetic profiles
• D. Are interchangeable

Answer: (B)

Understanding bioequivalence means looking at whether two drug forms deliver the same amount of active drug to the bloodstream at the same rate. For phenytoin, this is especially tricky because the drug has nonlinear pharmacokinetics—small changes in dose can cause disproportionately large changes in blood levels due to saturation of hepatic metabolism. Different dosage forms, like chewable tablets and capsules, can dissolve and release the drug differently. The chewable form might disintegrate and release phenytoin more quickly or slowly than the capsule, changing how much and how fast the drug enters circulation (affecting exposure measured as AUC and peak concentration). Because these factors can alter absorption, the two forms do not have the same bioavailability and are not interchangeable without monitoring serum levels and possibly adjusting dose. So they are not bioequivalent, and assuming they are could lead to under- or overexposure, with the risk of seizures or toxicity.