Possible side effects include:

• sore throat
• diarrhea
• pain in extremity
• muscle spasms
• neck pain
• chest pain
• sinusitis
• lower respiratory tract infection
• constipation 

Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Bruising of skin.
• Chest pain or pressure or a fast heartbeat.
• A heartbeat that does not feel normal.
• Shakiness.
• Change in eyesight, eye pain, or very bad eye irritation.
• Seeing halos or bright colors around lights.
• Not able to pass urine or change in how much urine is passed.
• Pain on urination
• Trouble breathing

Umeclidinium bromide is a long-acting antimuscarinic agent, often referred to as an anticholinergic. Inhaled umeclidinium bromide causes bronchodilation (relaxation of airway smooth muscle), improved lung function, and decreased mucous secretion.

Umeclidinium bromide must be used regularly to be effective. It does not work immediately and should not be used to relieve sudden shortness of breath. If sudden breathing problems occur, use your quick-relief inhaler.
Umeclidinium may cause paroxysmal bronchospasm in some patients. If this happens, discontinue use.
Umeclidinium 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.
Umeclidinium should be used cautiously in patients who have urinary retention. If passing urine becomes difficult, or painful, consult your physician immediately.

Drug interactions:

Consult your doctor or pharmacist if you are taking

• acetylcholinesterase inhibitors (e.g., donepezil, galantamine, rivastigmine)
• antihistamines
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• azelastine
• benztropine
• cyclobenzaprine
• darifenacin
• disopyramide
• fesoterodine
• glycopyrrolate
• ipratropium
• ketotifen
• metoclopramide
• mirabegron
• orphenadrine
• oxybutynin
• potassium chloride
• scopolamine
• solifenacin
• thiazide diuretics  hydrochlorothiazide, indapamide, metolazone)
• tiotropium
• tolterodine
• topiramate
• tranylcypromine
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• trospium

Use in pregnancy: There are no adequate and well-controlled studies  in pregnant women. Umeclidinium should be used during pregnancy only if the expected benefit to the mother justifies the potential risk to the fetus. Check with your doctor or pharmacist before use.

Use in breastfeeding: It is not known if umeclidinium is passed into breast milk; however, systemic absorption following oral inhalation is negligible. Check with your doctor or pharmacist before use.