PENILE ABSORPTION OF EMLA CREAM IN PIGLETS - IMPLICATIONS FOR USE OF EMLA IN NEONATAL CIRCUMCISION

EMLA(R) (eutectic mixture of lidocaine and prilocaine) cream is curren tly not recommended for use in infants <1 month of age because of the potential risk of methemoglobinemia as a result of the o-toluidine met abolite of prilocaine. We studied bioavailability and changes in methe moglobin levels following topical penile exposure to 1 g of EMLA cream for 1 hour in piglets. Lidocaine, prilocaine, and o-toluidine concent rations were measured simultaneously using a high-performance liquid c hromatography method. The systemic bioavailability of EMLA was low: 4. 0 +/- (SD) 4.7% for lidocaine (range 0-13.6; n = 8) and 7.2 +/- 5.7% f or prilocaine (range 0-14.5; n = 8). The ratio between exposure to o-t oluidine with EMLA versus intravenous administration (i.e., AUC(EMLA)/ AUC(IV); see text) was also low: 4.2 +/- 9.3% (range 0-28.6; n = 9). T he mean maximum methemoglobin value after intravenous administration w as 1.23 +/- 0.64% (range 0.5-3.0; n = 12) and after penile application 0.99 +/- 0.36% (range 0.5-2.0; n = 12). The methemoglobin value was e levated significantly above baseline after intravenous administration (p = 0.03), but not after penile application of EMLA. These findings s uggest that penile administration of 1 g of EMLB may be safe for neona tal circumcision, but further study is required.