The effect of pilocarpine on ocular levobunolol absorption from ophthalmic solutions

Studies in vitro and in vivo were conducted to investigate the effect of pilocarpine on ocular absorption of levobunolol when both drugs were formulated in one solution dosage. The ocular absorption of levobunolol is pH-dependent. Due to the large buffering capacity of pilocarpine at pH 5.5, the ocular absorption of levobunolol from pilocarpine-containing solutions was reduced by approximately four-fold as compared to a non-pilocarpine-containing formulation at pH 7.2. The ocular absorption of levobunolol in the presence of pilocarpine at acidic pH was enhanced by the use of sulfosuccinates, specifically Schercopol CMS.