Mydriatic response to topical naloxone in opiate abusers

Area of Science:

• Ophthalmology
• Pharmacology
• Addiction Medicine

Background:

• Opioid use disorder (OUD) is a significant public health concern.
• Methadone maintenance treatment (MMT) is a common OUD pharmacotherapy.
• Assessing current opioid influence and physical dependence can be clinically challenging.

Purpose of the Study:

• To investigate the mydriatic effect of topical naloxone hydrochloride eyedrops.
• To evaluate the potential of topical naloxone as a diagnostic tool for opioid influence and physical dependence.
• To explore the peripheral versus central mechanisms of opioid effects on pupillary size.

Main Methods:

• Administration of naloxone hydrochloride 1 mg/ml eyedrops to 47 individuals on MMT and healthy controls.
• Observation of pupillary size changes (mydriasis).
• Assessment of acute withdrawal symptoms.
• Evaluation of the response under different treatment conditions (ancillary treatments, methadone withdrawal).

Main Results:

• Naloxone eyedrops caused mydriasis in 36 out of 47 (76.6%) individuals on MMT.
• No acute withdrawal effects were observed in the MMT group.
• Healthy unmedicated subjects did not exhibit pupillary dilation.
• The mydriatic response was reduced by ancillary treatments and methadone withdrawal.
• The effect was localized to the treated eye, suggesting a peripheral action.

Conclusions:

• Topical naloxone eyedrops can induce mydriasis in opioid-dependent individuals without causing withdrawal.
• This localized pupillary response indicates potential clinical utility as a diagnostic test for current opioid influence and physical dependence.
• The findings suggest that opioid effects on pupillary size involve peripheral mechanisms.