Evidence for safety margins of lignocaine local anaesthetics for peri-oral use.

The evidence for the safety margins of doses of lignocaine local anaesthetics for standard injections for oral and dental purposes has been reviewed. Trials of peri-oral dosages leading to toxicity in humans have not been reported. The overwhelming evidence from trials of the normal dose range used clinically points to a restriction of total doses much lower than the 25 ml (500 mg) as published for 2% lignocaine with 1:80,000 adrenaline for a healthy adult. The recommendations are: 1. In mixtures of two pharmacologically active drugs (dual formulations) for peri-oral injections, to base the safety limit of local anaesthetic on the circulating level of lignocaine, rather than the amount of adrenaline contained in the injected volume. 2. Thus the suggested usual upper limit for dosage for a healthy adult patient is four and a half 2 ml (or 2.2-ml) cartridges of lignocaine with adrenaline (180-198 mg lignocaine or 2.57-2.82 mg/kg) body weight, if carefully given. 3. For some medically compromised patients, minimal doses only of lignocaine and adrenaline (about one cartridge) should be used and especial caution is necessary in patients likely to react adversely to the exogenous adrenaline of the dual formulation. 4. For both children and adults, the dosages should broadly be related to body size and note taken of the total dose which accrues from topical use of other formulations of lignocaine, such as pastes or creams or sprays. The doses injected should be the minimum that allow the treatment to proceed. If necessary the doses are better given at a series of appointments rather than as a large volume on one single occasion.