Oral pharmacology of chlorhexidine

Abstract The paper concerns factors which affect the binding and plaque-inhibiting effect of chlorhexidine-digluconate (CH) in the human oral cavity. About one-third of the administered dose was retained after mouth rinses (0.05-0.40 % w/v) and after toothbrushing with a CH gel (1 % w/w) measured by [¹⁴C]-chlorhexidine. The following CH concentration in saliva showed an almost logarithmic fall during the first 4-8 h, followed by a more steady low concentration, with CH still present after 24 h. The amount retained after mouth rinses increased almost linearly with the increase in the concentration. Time studies showed that about 55 % of the amount retained after 60 sec was retained after the first 15 sec. Lowering the pH of the rinsing solution reduced the retention, and increase in ionic strength of after-rinses increased the release of CH. Calcium in a 250 mM concentration significantly reduced the retention and increased the release when present in after-rinses. The detergent sodium dodecyl (lauryl) sulphate greatly reduced both the retention and the plaque-inhibiting effect. Comparative studies between CH and quaternary ammonium compounds showed that 60-65 % of the quaternaries was retained, compared to 32 % of CH. When used four times daily, the plaque-inhibiting effect of the quaternaries approached that of CH. Their concentration in saliva fell more rapidly than that of CH.