Is glycopyrrolate contraindicated in narrow angle glaucoma? why?

Maybe: Glycopyrrolate is an antimuscarinic agent and could make your pupils dilate. If you have an angle prone to acute angle closure, this drug could induce an attack. I am curious why you ask about this drug, as it is not something normally prescribed by any clinic doctor and commonly only used by anesthesiologists during general anesthesia.

Yes: This class of medicines can cause pupil dilation which can cause an already narrow angle to become more narrow possibly blocking enough outward eye fluid flow leading to an increase in the eye pressure which may cause nerve damage.

Dilation: Glucopyrrolate has a dilating effect on the eyes which can worsen the symptoms of glaucoma by increasing the pressure in the eye.

Open angles are okay: Glycopyrrolate is an anticholinergic, which has a potential effect on patients with NARROW angle glaucoma. The effects can transiently dilate the pupil, which in turn can congest the angle where the natural drainage system is. This effect can be too much in a narrow angle eye where the angle is already compromised. This can lead to acutely increased eye pressures and worsen glaucoma. Good luck!