Phenytoin and formation of T lymphocyte rosettes

Phenytoin sodium has been associated with the formation of altered T lymphocyte rosettes in vitro. To investigate the clinical relevance of this observation, the formation of T lymphocyte rosettes in nine patients was studied before treatment with phenytoin and after therapeutic concentrations of the drug in plasma were attained. The percentage of total rosette-forming cells found before treatment was not significantly different from the percentage found 24 hours after treatment. Likewise, the percentage of active rosette-forming cells before phenytoin therapy was not significantly less than after therapy. These results suggest that in vivo treatment with phenytoin does not acutely inhibit the formation of T lymphocyte rosettes.