MDR1 gene polymorphisms and risk of gingival hyperplasia induced by calcium antagonists.

Background: Gingival overgrowth is a common side effect of calcium antagonists. Although the pathogenesis is unknown, several lines of evidence point to a modulation of inflammatory processes. Because the calcium antagonists, albeit to a variable degree, act as inhibitors of P-glycoprotein (P-gp), the gene product of multidrug resistance 1 (MDR1), and inflammation may modify P-gp expression, we analyzed the MDR1 polymorphisms as risk factors for gingival overgrowth induced by calcium antagonists.
Methods: Clinical, laboratory, and anamnestic data including periodontal parameters and use of calcium antagonists were assessed in a cross-sectional epidemiologic investigation (N = 1484). MDR1 polymorphisms in exon 21 G2677T/A and exon 26 C3435T were determined. P-gp expression was detected in gingival tissues. In a matched-pair analysis, 93 subjects using calcium antagonists and 186 not using them were compared.
Results: P-gp is expressed in the endothelial layers of blood vessels obtained from healthy or inflamed gingiva. Subjects treated with calcium antagonists had significantly deeper gingival pockets than their drug-free counterparts (P <.0001). This drug-related side effect was associated with the MDR1 2677G/G or G/TA genotype (P <.001) but not with the variant genotype T/TA. This drug effect was proved by multiple regression analysis with adjustment for the risk factors of periodontitis (age, sex, smoking, and education) (P <.0001) and was associated with elevated C-reactive protein levels. The association of probing depth with the MDR1 polymorphism was confirmed in the matched-pair analysis (P <.0001).
Conclusion: Treatment with calcium antagonists leads to gingival hyperplasia, which is associated with the MDR1 G2677T/A polymorphism. The MDR1 genotype may modify the inflammatory response to the drugs.