Along with its benefit, aclidinium bromide may cause unwanted effects. Possible side effects include:

• headache
• inflammation or irritation of the nose and throat
• cough
• diarrhea
• sinusitis
• vomiting
• hoarseness
• dizziness

Stop taking this medication and seek medical help if you experience:

• New or worsened pressure in your eyes, eye pain or discomfort, blurred vision, seeing halos of bright colours around lights, red eyes. 
• Tightness of the chest associated with coughing, wheezing, or breathlessness immediately after inhalation  
• Serious allergic reactions: rash, hives, swelling of the face, mouth, lips and tongue with or without breathing problems

Aclidinium bromide is a long-acting antimuscarinic agent used by inhalation through the mouth.  It works by relaxing the muscles that surround the airways. This opens the air passages and makes breathing easier.

• Aclidinium bromide is for maintenance therapy only and should not be used as a rescue inhaler during a sudden episode of bronchospasm.
• Aclidinium bromide may cause paroxysmal bronchospasm in some patients. If this happens, discontinue use.
• Aclidinium should be used cautiously in patients with narrow- angle glaucoma. If symptoms of acute narrow-angle glaucoma such as, eye pain, visual halos, or blurred vision develop, consult your physician immediately.
• Aclidinium should be used cautiously in patients who have urinary retention. If passing urine becomes difficult, or painful, consult your physician immediately.
• Patients with a hypersensitivity to aclidinium bromide should not use it.
• Patients who have a hypersensitivity to atropine should use aclidinium with caution. The two are structurally similar and hypersensitivity reaction may occur.
• Patients with a severe allergy to milk protein should not use aclidinium.

Use in pregnancy and breastfeeding: Limited human data available at this time.  Use only if benefits outweigh risks.  Consult your doctor or pharmacist before use.