Serum phenytoin concentration and IgG antibody titre to periodontal bacteria in patients with phenytoin-induced gingival overgrowth.

Epileptic patients taking phenytoin with gingival-overgrowth and those without gingival-overgrowth were compared for daily drug dose, plasma total phenytoin concentration, plasma free-phenytoin concentration and serum IgG antibody titre against 13 periodontal bacteria. Significantly higher daily drug dose was noted in patients with gingival overgrowth (P < 0.05) when compared with those without overgrowth. In addition, both total and free forms of plasma phenytoin concentration were significantly higher in sera of patients with gingival growth than of those without overgrowth (P < 0.01). Strong positive correlation was found between daily drug dose and serum phenytoin concentration in patients with gingival overgrowth, while weak correlation was found in patients without gingival overgrowth, suggesting a difference in drug metabolism in these two groups. However, no differences were found in serum IgG antibody titres to 13 periodontal bacteria examined between two groups. These results suggest that metabolic ability of phenytoin is one of the factors for developing gingival overgrowth, and that periodontal infection may not be a primary causative factor for gingival overgrowth but act as an additive factor which increase tissue mass for this unwanted side effect.