This study was undertaken to evaluate the ocular pharmacokinetic of
sulfisoxazole. Male, 2-3 years old 10 mix breed dogs weighing 12-15 kg were used. A 2 mg dose/eye of
sulfisoxazole was administrated to the animals by either subconjunctivally or by topically. Samples of aqueous humor were collected after 0.083, 0.25, 0.5, 1, 2, 4, 6, 24 and 72 h and level of
sulfisoxazole was determined. Pharmacokinetic parameters including absorption rate constant (k(a)), slope factor (beta), absorption half-life (t1/2a), half-life of elimination in aqueous humor (t1/2beta), maximal concentration in aqueous humor (C(max)), time to reach C(max) (t(max)), mean residence time in aqueous humor (MRT) and area under the concentration time curve from zero up to infinity (AUC(0-infinity)) were calculated. Compared to topical application, value of k(a) in subconjunctival application increased while values of t1/2a and t(max) decreased and the value of t1/2beta prolonged (p < 0.05). There was no significant difference between groups regarding other parameters (p > 0.05). These results indicate that
sulfisoxazole may not be potent enough to treat intraocular
infections caused by bacteria when applied either subconjunctivally or topically at a dose of 2 mg/eye. Furthermore, subconjunctival application of
sulfisoxazole could be more efficient for treatment of intraocular
infections due to higher absorption of
drug and longer remaining time in the eye compared to topical application.