Penetration of topically applied betamethasone sodium phosphate into human aqueous humour

Gas Chromatography combined with Negative Chemical Ionisation Mass Spectrometry (GCMS) was used to determine the absorption of topically applied beta-methasone sodium phosphate into the aqueous humour of human subjects undergoing routine intraocular surgery. The Betamethasone concentration was greatest in the interval 91-120 minutes following topical administration (mean peak concentration = 7.7 ng/ml). At twelve hours post instillation the mean concentration of Betamethasone was 2.5 ng/ml and detectable levels were recorded in the aqueous humour 24 hours after application (mean concentration 0.4 ng/ml).