Phosphate concentrations in antiglaucoma medication

Klin Monbl Augenheilkd. 2007 Apr;224(4):249-51. doi: 10.1055/s-2007-962834.


Background: Eye drops may contain phosphates as part of their buffer system. In the presence of epithelial keratopathy a high concentration of phosphate favours corneal calcification. To date European legislation does not require a quantitative declaration of the phosphates since buffers are regarded as additives. The knowledge of the phosphate concentration in medications helps to prevent corneal calcifications. Our study gives an overview on the amount of phosphate contained in antiglaucoma drops.

Methods: 21 samples of commercially available antiglaucoma drops were tested. The quantification of phosphate was performed using the molybdate method on a Modular P autoanalyzer.

Results: 10 of 21 (47 %) glaucoma drops had a phosphate concentration above physiological levels (> 1.45 mmol/L). A concentration higher than 100 mmol/L was found in four preparations that contained timolol.

Conclusions: Many antiglaucoma drops contain unphysiological levels of phosphate, very high concentrations are found in some beta-blockers. These preparations have the potential to favour the formation of insoluble crystalline calcium phosphate deposits when used on a damaged corneal surface, and should therefore be avoided.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Adrenergic alpha-Agonists / chemistry*
  • Adrenergic alpha-Agonists / therapeutic use
  • Adrenergic beta-Antagonists / chemistry*
  • Adrenergic beta-Antagonists / therapeutic use
  • Antihypertensive Agents / chemistry*
  • Antihypertensive Agents / therapeutic use
  • Cholinergic Agents / chemistry*
  • Cholinergic Agents / therapeutic use
  • Drug Contamination / prevention & control
  • Drug Evaluation, Preclinical / methods
  • Glaucoma / drug therapy
  • Humans
  • Ophthalmic Solutions / chemistry*
  • Phosphates / analysis*
  • Prostaglandins / chemistry*
  • Prostaglandins / therapeutic use


  • Adrenergic alpha-Agonists
  • Adrenergic beta-Antagonists
  • Antihypertensive Agents
  • Cholinergic Agents
  • Ophthalmic Solutions
  • Phosphates
  • Prostaglandins