Acetaminophen (paracetamol) levels in human tears

This study was designed to measure acetaminophen (paracetamol) levels in te ars, and to compare it to serum levels. Paracetamol levels were measured in 20 paired tears and serum samples from 10 healthy volunteers, 1 and 2 hour s after ingesting 1.5 g paracetamol. Tears were collected using glass micro capillary tubes while stimulating the conjunctiva with a small sponge place d in the lower fornix, Blood samples were taken simultaneously. The samples were analyzed for paracetamol levels using homogeneous enzyme immunoassay. Tears and serum paracetamol levels 1 hour after ingestion were 16.3 mu g/m L +/- 7.2 (mean +/- SD), and 21.4 mu g/mL +/- 7.7 (mean +/- SD) respectivel y. Tears and serum levels 2 hours after ingestion were 14.4 mu g/mL +/- 7.8 (mean +/- SD), and 17 mu g/mL +/- 7.6 (mean +/- SD) respectively. Tears an d serum paracetamol levels of all the 20 paired samples (1 h and 2 h after ingestion) were 15.35 mu g/mL +/-: 7.4, and 19.25 mu g/mL +/- -7.8, respect ively (mean +/- SD). There was a strong and highly significant correlation between paracetamol levels in serum and in tears 1 and 2 hours after ingest ion (r = 0.8, p = 0.005, r = 0.85, p = 0.002 respectively). Mean +/- SD rat io of tears/serum paracetamol levels 1 hour and 2 hours after ingestion wer e 0.77 +/- 0.21 and 0.81 +/- 0.25 respectively. Delta tears (difference in mean levels at 1 and 2 hours) paracetamol levels is significantly correlate d with Delta serum levels (r = 0.7, p = 0.025). A reliable, convenient, and feasible noninvasive method is described for measuring paracetamol in tear s. There is no information in the literature about tears paracetamol secret ion, and little information of tears drugs concentration.