A pilot study was undertaken to address the tolerance and efficacy of
levodopa/
carbidopa treatment for
amblyopia in older amblyopic children who failed to respond to conventional occlusion
therapy. Five amblyopic children, between the ages of 7 and 12 years, and two normal adults were given between 100 mg/25 mg and 400 mg/100 mg of
levodopa/
carbidopa, respectively, depending on
body weight. A symptoms questionnaire was completed, with temperature, respiration, heart rate, and blood pressure taken periodically to assess tolerance. Blood samples were taken, via a
heparin well, to assess the pharmacokinetics of
levodopa,
dopamine,
noradrenaline, and
DOPAC. Snellen visual acuity, contrast sensitivity, stereo acuity, and pattern VERs were measured periodically to assess efficacy. The results revealed a high prevalence of side effects including
emesis and
nausea (four of seven subjects). Pharmacokinetics revealed that maximum serum levels of
levodopa occurred 30 minutes to 1 hour after
drug ingestion and decreased by 50% after 2 to 4 hours. One hour after
drug ingestion, Snellen visual acuity temporarily improved from an average of 20/159 to 20/83 in the amblyopic eyes. Contrast sensitivity and pattern VERs (10-minute checks) temporarily improved in both dominant and amblyopic eyes, whereas visual function remained stable in normal eyes. The improvements in visual function started to decrease 5 hours after
drug ingestion. The results are discussed in the context of developing a therapeutic trial of
levodopa/
carbidopa for childhood
amblyopia.