Asymptomatic hyperammonemia in patients receiving valproic acid
J. V. Murphy and K. Marquardt
To determine the frequency of hyperammonemia in asymptomatic patients
receiving valproic acid, plasma ammonia concentrations were measured in 55
patients receiving this drug and in 12 patients receiving other
anticonvulsants. Twenty-nine of the 55 patients receiving valproic acid and
none of the control patients had plasma NH3 levels above the normal range.
Ten of the 11 patients receiving both valproic acid and phenytoin sodium in
combination had elevated NH3 levels, as did five of six patients receiving
both valproic acid and phenobarbital sodium. Elevations in plasma NH3
levels, as high as 140 mumole/L, were well tolerated, and valproic acid
dose reductions were not necessary. Based on our findings, hyperammonemia
is not an indication for reducing or eliminating valproic acid therapy.
