Polydimethylosiloxanes as active substance in pharmaceutical formulations. Polydimethylosiloxanes (PDMS) constitute active substance in ca. 20 pharmaceutical formulations of variable manufacturers, licensed and approved for application in Poland. They belong to two groups of preparations known under trade names: Dimeticone and Simeticone which have anti-foaming and protective effect. The authors of an article cite the existing regulations referring to PDMS application and simultaneously rise a point about lack of detailed information on their actual viscosity in the product, which should be included in the leaflets. In the pharmaceutical formulations administered internally, only PDMS of linear form and viscosity over 50 cSt are allowed for use. Still, there is a possibility of PDMS occurrence in the linear form but an undesirable degree of polymerisation and some toxic cyclic forms. Moreover, the authors point to the possibility of considerable overdosing on the amounts consumed by adults and children, in comparison to the recommended Acceptable Daily Intake.