Abstract
ABSTRACT
The toxicity of three different transdermal nitroglycerin ointments on the external ocular structures of New Zealand White rabbits was investigated. Using a randomized, double-blind protocol, both eyes of four rabbits in each of four treatment groups received 3.75 mg of either Nitrol Ointment, Nitrong Ointment, Nitro-bid Ointment, or Lacri-lube Ointment twice a day for 21 days. The eyelids, palpebral and bulbar conjunctiva, cornea, anterior chamber, and iris were evaluated by slit lamp. Pupillary size was noted and intraocular pressure was measured with an applanation tonometer. All parameters were evaluated pretreatment and two hours after the last dose on treatment days 1, 8, 15, and 22. On days 8 and 15, all four treatment groups had evidence of mild conjunctival injection; however, only the three nitroglycerin groups had mild conjunctival chemosis. At day 22, all four treatment groups had no statistically significant evidence of toxicity to the eyelid, conjunctiva, and iris. Only Nitrong Ointment produced any corneal toxicity, a mild diffuse punctate keratopathy statistically significant only on day 22. In addition, the four treatment groups showed no change in pupil size and intraocular pressure.
Transdermal nitroglycerin preparations were well tolerated by the external ocular structures of rabbits. Additional animal studies to evaluate the dosage and frequency effects on tolerance and intraocular pressure are indicated.
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