The pharmacokinetics of phenytoin in gingival crevicular fluid and plasma in relation to gingival overgrowth

Connective Tissue Metabolism and Gingival Overgrowth

Gingival overgrowth occurs mainly as a result of certain anti-seizure, immunosuppressive, or antihypertensive drug therapies. Excess gingival tissues impede oral function and are disfiguring. Effective oral hygiene is compromised in the presence of gingival overgrowth, and it is now recognized that this may have negative implications for the systemic health of affected patients. Recent studies indicate that cytokine balances are abnormal in drug-induced forms of gingival overgrowth. Data supporting molecular and cellular characteristics that distinguish different forms of gingival overgrowth are summarized, and aspects of gingival fibroblast extracellular matrix metabolism that are unique to gingival tissues and cells are reviewed. Abnormal cytokine balances derived principally from lymphocytes and macrophages, and unique aspects of gingival extracellular matrix metabolism, are elements of a working model presented to facilitate our gaining a better understanding of mechanisms and of the tissue specificity of gingival overgrowth.

Inhibition of G₁ cell cycle arrest in human gingival fibroblasts exposed to phenytoin

Gingival overgrowth is caused in response to the antiepileptic drug phenytoin (PHT). PHT-induced gingival overgrowth is characterized by the proliferation of fibroblasts and increased collagen formation in gingiva. Fibroblast proliferation is regulated through the cell cycle. Thus, in the present study, we examined the effects of PHT on the cell cycle, the expression of cell cycle control proteins and the proliferation in human gingival fibroblasts (hGFs). Cells were stimulated in serum-free DMEM with or without 0.25 μm PHT. Subsequently, the cell cycle phase distribution and the protein expression after 24 h and the cell proliferation after 24, 48 and 72 h were evaluated. PHT significantly inhibited synchronization at the G₀/G₁ phase of the cell cycle in hGFs through serum starvation. Stimulation with PHT for 48 and 72 h significantly induced a proliferative response in hGFs. PHT decreased the expression of the Cdk-inhibitory proteins p21 and p27 and increased the levels of the S phase-promoting proteins phospho-Thr160-Cdk2 and phospho-Ser807/811-Rb in serum-free DMEM. The inhibition of G₁ cell cycle arrest in hGFs may result from an increase in phosphorylated Cdk2 and Rb proteins and decreased levels of p21 and p27 proteins by PHT. The gingival overgrowth may be caused by the failure of the G1 cell cycle arrest in GFs exposed to PHT.

Phenytoin-induced gingival overgrowth: a review of the molecular, immune, and inflammatory features

Gingival overgrowth (GO) is a side effect associated with some distinct classes of drugs, such as anticonvulsants, immunosuppressant, and calcium channel blockers. GO is characterized by the accumulation of extracellular matrix in gingival connective tissues, particularly collagenous components, with varying degrees of inflammation. One of the main drugs associated with GO is the antiepileptic phenytoin, which affects gingival tissues by altering extracellular matrix metabolism. Nevertheless, the pathogenesis of such drug-induced GO remains fulfilled by some contradictory findings. This paper aims to present the most relevant studies regarding the molecular, immune, and inflammatory aspects of phenytoin-induced gingival overgrowth.

Drug-induced gingival enlargement: biofilm control and surgical therapy with gallium-aluminum-arsenide (GaAlAs) diode laser-A 2-year follow-up

Drug-induced gingival enlargement has been reported in patients treated with various types of anticonvulsant drugs, and is generally associated with the presence of plaque, gingival inflammation, and a genetic predisposition. Effective treatment includes daily oral hygiene and periodic professional prophylaxis. However, in some patients, surgical removal of the gingival tissue overgrowth becomes necessary. The patient in this case report was mentally impaired and had severe drug-induced gingival enlargement. This report describes the initial protocol, the gingivectomy, and a 2-year follow-up. A diode laser was used as an effective and safe method to remove the patient's overgrown gingival tissue.

Plasma and gingival crevicular fluid phenytoin concentrations as risk factors for gingival overgrowth

BACKGROUND

Gingival enlargement is one of the side effects associated with the administration of phenytoin. The mechanism by which phenytoin induces gingival enlargement is not well understood. This study was conducted to investigate the relationship between plasma and gingival crevicular fluid (GCF) phenytoin concentrations and the degree of gingival overgrowth in patients with similar gingival and plaque indices and also to determine the risk factors for gingival enlargement.

METHODS

Eighteen patients taking phenytoin in regular doses > or =6 months prior to the investigation participated in the study. Gingival enlargement was evaluated with two indices to score vertical and horizontal overgrowth. The gingival index (GI), plaque index (PI), gingival bleeding time index (GBTI), probing depth (PD), and clinical attachment level (CAL) were also evaluated. GCF and plasma phenytoin concentrations were determined by using high-performance liquid chromatography (HPLC).

RESULTS

There was no significant difference between responders and non-responders for PD, CAL, PI, GI, and GBTI. Phenytoin was detected in all of the GCF and plasma samples using the HPLC analysis method. The mean concentration of phenytoin in GCF was significantly greater than the concentration of phenytoin in plasma. No significant difference was observed for the concentration of GCF phenytoin between responders and non-responders. However, the concentration of plasma phenytoin was significantly higher in responders than non-responders.

CONCLUSION

This study showed that plasma phenytoin level appeared to be a risk factor for phenytoin-induced gingival overgrowth.

Connective tissue growth factor in drug-induced gingival overgrowth

BACKGROUND

Drug-induced gingival overgrowth is a known side effect of certain chemotherapeutic agents used for the treatment of systemic disorders. The pathogenesis and mechanisms responsible for this condition are not fully understood. This study assesses for the presence and localization of connective tissue growth factor (CTGF) in drug-induced gingival overgrowth tissues. CTGF immunostaining was compared with sections stained with transforming growth factor (TGF)-beta1 and CD31 antibodies in order to investigate possible pathogenic mechanisms.

METHODS

Gingival overgrowth samples were obtained from patients undergoing therapy with phenytoin (n = 9), nifedipine (n = 4), cyclosporin A (n = 5), and control tissues from systemically healthy donors (n = 9). Tissue sections were subjected to peroxidase immunohistochemistry and were stained with CTGF and TGF-beta1 polyclonal primary antibodies. Possible relationships between CTGF staining and angiogenesis were also studied using an anti-CD31 antibody as a marker for endothelial cells. Staining was analyzed by computer-assisted quantitative and semiquantitative methodology at 5 defined sites in all samples based on the location of specific landmarks including epithelium and underlying connective tissues.

RESULTS

Cellular and extracellular CTGF content in phenytoin gingival overgrowth tissues was significantly (P<0.05) higher compared to the other gingival overgrowth tissues and the controls. Higher CTGF staining in phenytoin gingival overgrowth tissues was accompanied by an increased abundance of fibroblasts and connective tissue fibers. No strong association of CTGF staining with TGF-beta1 or CD31 staining was found.

CONCLUSIONS

The data from the present study show significantly higher CTGF staining in phenytoin-induced gingival overgrowth tissues compared to controls, cyclosporin A-, or nifedipine-induced gingival overgrowth. Moreover, semiquantitative analyses of histologic samples support the concept that the phenytoin overgrowth tissues are fibrotic. These associations suggest a possible role for CTGF in promoting development of fibrotic lesions in phenytoin-induced gingival overgrowth.

Protein recovery from several paper types used to collect gingival crevicular fluid

The purpose of this study was to compare the efficiency of protein elution from several types of gingival crevicular fluid (GCF) collection papers when the volume of the inoculated protein and the elution methods were constant. Various concentrations of bovine serum albumin (BSA) and 14C-BSA were placed onto strips of Whatman #1 [W1], Whatman 3 MM chromatographic [W3], Periopaper (ProFlow) [P] and Periopaper (Harco) [H], and recovered proteins measured following a non-optimized centrifugal elution technique. There were significant differences in % recovery of BSA and 14C-BSA from the papers, which was dependent on both the type of paper and the concentration of the inoculated protein; that is, proteins at the lowest concentrations were less efficiently eluted from GCF collection papers than those at higher concentrations. Equations for regression lines of elution efficiency were quadratic. Thus, our data suggest significant differences in the efficiency for elution of BSA from absorbent papers when the volume of the inoculated fluid and the elution technique were constant. Previous variable or conflicting experimental data between research groups may have resulted from incomplete elution of proteins from GCF collection papers, possibly due to entrapment within, or binding of GCF proteins to the paper.