Are intraligamentary injections intravascular?

A pressure type syringe was used to give intraligamentary injections (IL) to upper teeth of two formulations commonly used in general practice, lignocaine and prilocaine. Assay of plasma levels of drug was carried out by high performance liquid chromatography. Results of assays after intraligamentary injections were then compared with results of assays after intravenous injections of plain drug in the same subjects. Both formulations of local anaesthetic were found as peak levels in the circulation, presumably after intraosseous spread, by 2 minutes following the intraligamentary injections. For lignocaine the peak amount was nearly 7% of the intravenous dose and for prilocaine the peak amount was 25% of the intravenous dose, at 2 minutes after injection. It was concluded that IL injections for healthy adults were unlikely to cause systemic unwanted effects when given in small doses.