Although diflunisal is derived from
salicylic acid, it is not metabolized to salicylic acid or salicylate. It
undergoes an enterohepatic cycle with reabsorption of its glucuronide metabolite
followed by cleavage of the glucuronide to again release the active moiety.
Diflunisal is subject to capacity-limited metabolism, with serum half-lives at
various dosages approximating that of salicylates (Table 36–1). In rheumatoid
arthritis the recommended dose is 500–1000 mg daily in two divided doses. It is
claimed to be particularly effective for cancer pain with bone metastases and
for pain control in dental (third molar) surgery. A 2% diflunisal oral ointment
is a clinically useful analgesic for painful oral lesions.
