title: Secretion of drugs in tears.
abstract: Secretion in tears has been investigated for a limited number of drugs. Transfer of the free non protein-bound fraction from plasma to tears only can be expected for unionized drugs with sufficient lipid solubility. For acid and basic drugs the correlation of tear: plasma (unbound) ratio is disturbed by variations in tear pH. Within these limitations tear sampling will not be an useful method for drug concentration measurement.
mesh_terms: D000042:Absorption; D001696:Biomechanical Phenomena; D001798:Blood Proteins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008055:Lipids; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D012995:Solubility; D013048:Specimen Handling; D013666:Tears / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D007477:Ions; D008055:Lipids; D004364:Pharmaceutical Preparations