Quantification method for timolol from in vivo samples for the development of a new glaucoma drug depot

Abstract

Abstract Glaucoma is the second most common cause of blindness. An increased intraocular pressure is the only treatable symptom of glaucoma. Because patients often exhibit a poor therapy adherence, a drug depot consisting of ELA-NCO and hyaluronic acid with timolol was developed to ensure sustained drug release. This drug depot is formed by in situ polymerisation after injection into the subconjunctival space. To test the in vivo drug release of timolol in serum and aqueous humour, a liquid chromatography mass spectrometry (LCMS) method was developed and tested using spike- and recovery experiments, and on in vivo samples after topical application. Samples of serum and aqueous humour were taken from New Zealand White rabbits. For topical application, a commercially available formulation of timolol was used. This study presents results concerning the recovery of timolol from spiked samples. Serum and aqueous humour samples were spiked with timolol maleate to a final concentration of 50 ng/mL. Subsequently, the samples were extracted and analysed by LCMS. External calibration of the developed method showed high linearity. Recovery experiments showed no loss of timolol. Hence, the extraction method is robust and able to recover the whole amount of timolol from aqueous humour and serum.