Code G refers to ophthalmic decongestants and anticholinergics.
Antihistamines diphenhydramine, dimenhydrinate and doxylamine are coded G for their anticholinergic activity.
OPHTHALMIC DECONGESTANTS have a sympathomimetic effect which causes mydriasis in high doses. Pupillary dilation can precipitate an attack of narrow angle glaucoma in susceptible persons. Although the incidence of narrow angle glaucoma is relatively low at 5% of glaucoma patients, this is a potentially serious reaction. Undiagnosed or uncontrolled glaucoma patients may suffer damage to the optic nerve.
ANTICHOLINERGICS also cause mydriasis and are contraindicated in narrow angle glaucoma. Those with open angle glaucoma may also have a slight increase in intraocular pressure necessitating an adjustrnent in glaucoma therapy.
Refer to an ophthalmologist inunediately if there are symptoms including:
Abnormal pupil size
Pain in the eye
Changes in vision
Marked sensitivity to light
Injury to eye
Symptoms lasting longer than 48-72 hours