Unilateral mydriasis: an unexpected effect of ipratropium bromide inhalation-a brief report

Anisocoria often raises concerns about potential underlying conditions such as intracranial hemorrhage, brain tumor, or Horner syndrome. However, iatrogenic exposures may also lead to unilateral mydriasis. A six-month-old infant was hospitalized due to acute bronchiolitis with a history of prematurity, bronchopulmonary dysplasia, and periventricular leukomalacia (PVL). He received non-invasive respiratory support, salbutamol, and ipratropium bromide by inhalation. Four days after admission, the infant exhibited an episode of sudden unilateral mydriasis with no other new signs or symptoms. Ophthalmological examination disclosed no abnormalities besides the dilated pupil, and brain CT scan showed PVL similar to the previous imaging without new pathological findings. There are several case reports of ipratropium bromide given by inhalation causing mydriasis by leakage through the inhalation mask. Ipratropium bromide is an antagonist of the muscarinic receptors. It induces bronchodilation and inhibits mucus production. One of the possible side effects of antimuscarinic drugs is mydriasis. Our patient did not exhibit any systemic signs, thus suggesting a local effect by direct contact between the eye and the offending agent. Treatment with ipratropium bromide was stopped, and within 24 h, the pupil size returned to normal.

This case underscores the importance of recognizing the side effects of medications, particularly in young patients with complex medical conditions.

• Unilateral mydriasis refers to unequal pupil sizes, where the abnormal pupil is dilated. • Unilateral mydriasis can result from a variety of causes, ranging from benign to serious conditions, including iatrogenic factors such as medications.

• The occurrence of unilateral mydriasis induced by ipratropium bromide has been rarely reported in pediatric patients. • If unilateral mydriasis is an isolated abnormal finding and there is a history of ipratropium bromide exposure, themydriasis could be due to the ipratropium exposure.