Related Experiment Videos
The effect of nitroglycerin ointment on the external ocular structures of rabbits
A H Zalta1, K M Karlin, L Ziegler
1University of Cincinnati Medical Center, Ohio.
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.
Insights
Transdermal nitroglycerin ointments showed minimal ocular toxicity in rabbits. Most preparations were well tolerated, with only mild, transient effects observed.
Area of Science:
- Ophthalmology
- Toxicology
- Pharmacology
Background:
- Transdermal drug delivery systems require safety evaluations.
- Nitroglycerin's ocular effects are not fully understood.
Purpose of the Study:
- To assess the ocular toxicity of transdermal nitroglycerin ointments.
- To compare the safety profiles of different nitroglycerin formulations.
Main Methods:
- New Zealand White rabbits received four different ointments (Nitrol, Nitrong, Nitro-bid, Lacri-lube) for 21 days.
- Ocular structures were examined using slit lamp microscopy and tonometry.
- Evaluations were performed at multiple time points during the treatment period.
Main Results:
- Mild conjunctival injection and chemosis were observed in nitroglycerin groups.
- Nitrong Ointment caused mild punctate keratopathy by day 22.
- No significant toxicity was noted for eyelids, conjunctiva, iris, pupil size, or intraocular pressure.
Conclusions:
- Transdermal nitroglycerin preparations were generally well tolerated by rabbit ocular structures.
- Further studies are needed to explore dosage and frequency effects on tolerance and IOP.