Sir, we read with interest the calculations made by J.V. Williams (BDJ 2006; 201: 187) regarding the amount of lignocaine (lidocaine) that can be administered safely. Although Mr Williams discusses lignocaine with adrenaline, he uses the dose limits set for plain lignocaine. The British National Formulary gives the maximum dose of lignocaine with adrenaline that can be administered as 500 mg, not 300 mg.1 Furthermore, Dentsply's information sheet accompanying 'Xylocaine' gives the maximum dose as 7 mg/kg rather than 4.4 mg/kg. Therefore, the maximum number of cartridges of 2% lignocaine with one in 80,000 adrenaline that can be used for an average 70 kg patient is just over 11 and not 6.8 as stated by Mr Williams. All dentists should be familiar with the quantity of lignocaine with adrenaline that can be administered safely and if in doubt refer to the manufacturer's guidance or a national drug formulary.
British National Formulary v.51. p 648. Pharmaceutical Press, 2006.