Abstract
Purpose: :
The aim of this research work is to delineate the effect of lipophilicity on ocular disposition of drugs following subconjunctival injection.
Methods: :
Mannitol and diazepam were selected as hydrophilic and lipophilic model compounds. Male Newzeland albino rabbits were used for the ocular disposition studies. One hundred microliters of subconjunctival injection of [14C] mannitol and [14C] diazepam was administered using 30' gauze needle. The animals were euthanized at the end of predetermined experimental period (0.5, 1, 3, 5 and 8 hrs.) under deep anesthesia. Ocular tissues (sclera, cornea, iris, retina-choroid, aqueous humor and vitreous humor) were collected.
Results: :
Radioactivity associated with ocular tissues was measured by scintillation counter. The rank order for the concentration of mannitol was found to be sclera > cornea > retina-choroid > iris > lens. However, the rank order for diazepam was sclera = cornea > iris = retina-choroid > lens > aqueous humor > vitreous humor. Significant higher uptake of diazepam was seen as compared to mannitol. Overall, this research work suggests faster and higher uptake of lipophilic model compound, diazepam, following subconjunctival injection as compare to hydrophilic compound.
Conclusions: :
Subconjunctival injection may be a viable option for posterior segment drug delivery, specially for lipophilic compound.
Keywords: conjunctiva • anterior segment • retina