Phenytoin (PHT) and valproic acid (VPA) compete for the same binding sites on albumin.  In patients taking both PHT and VPA, the free fraction of phenytoin will be increased, which causes a total PHT level to falsely represent a patient’s active PHT status.

To supplement the recent video on Total vs. Free Phenytoin and the existing correction calculator for hypoalbuminemia, a new correction calculator for concurrent valproic acid has been released.

Continue reading →

Converting between equianalgesic opioid dosing isn’t exactly a hard science.  Given the lack of blinded trials, bidirectional conversions, dose-dependent conversions, incomplete cross-tolerance, equianalgesic discrepancies in the literature, and patient-specific factors (specifically metabolism and absorption), a “simple” equianalgesic conversion table often doesn’t do the process justice. Continue reading →