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Thymoxamine reverses phenylephrine-induced mydriasis.
S J Relf1, N Z Gharagozloo, G L Skuta
1Department of Ophthalmology, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
American Journal of Ophthalmology
|September 15, 1988
Summary
Thymoxamine effectively reverses phenylephrine-induced pupil dilation, particularly in blue irides. This alpha-adrenergic blocker is useful for preventing glaucoma in patients with narrow angles.
Area of Science:
- Ophthalmology
- Pharmacology
Background:
- Phenylephrine is commonly used to induce mydriasis (pupil dilation).
- Mydriasis can pose risks, such as acute closed-angle glaucoma, especially in individuals with narrow anterior chamber angles.
Purpose of the Study:
- To evaluate the efficacy of thymoxamine as an alpha-adrenergic blocking agent in reversing phenylephrine-induced mydriasis.
- To assess the safety and effectiveness of thymoxamine in specific patient populations.
Main Methods:
- A randomized, double-masked, placebo-controlled trial was conducted.
- Participants received either 0.1% thymoxamine or a placebo eyedrop after phenylephrine-induced mydriasis.
- Pupil size and response time were measured.
Main Results:
- Thymoxamine reversed phenylephrine-induced mydriasis in 90% of eyes within one hour.
- Complete reversal occurred in 63% of eyes.
- Blue irides showed a faster and more complete response than brown irides.
- Placebo did not reverse mydriasis.
- 50% of subjects reported mild, transient ocular irritation.
Conclusions:
- Thymoxamine is an effective agent for reversing phenylephrine-induced mydriasis.
- It is particularly beneficial for patients at risk of angle-closure glaucoma.
- Thymoxamine demonstrates a favorable safety profile with minimal side effects.