This medicine can increase your risk of life-threatening heart or circulation problems, including heart attack or stroke. This risk will increase the longer you use diclofenac. Do not use this medicine just before or after having heart bypass surgery (also called coronary artery bypass graft, or CABG).
Seek emergency medical help if you have symptoms of heart or circulation problems, such as chest pain, weakness, shortness of breath, slurred speech, or problems with vision or balance.
This medicine can also increase your risk of serious effects on the stomach or intestines, including bleeding or perforation (forming of a hole). These conditions can be fatal and gastrointestinal effects can occur without warning at any time while you are taking diclofenac. Older adults may have an even greater risk of these serious gastrointestinal side effects.
Call your doctor at once if you have symptoms of bleeding in your stomach or intestines. This includes black, bloody, or tarry stools, or coughing up blood or vomit that looks like coffee grounds.
Do not use any other over-the-counter cold, allergy, or pain medication without first asking your doctor or pharmacist. Many medicines available over the counter contain aspirin or other medicines similar to diclofenac (such as ibuprofen, ketoprofen, or naproxen). If you take certain products together you may accidentally take too much of this type of medication. Read the label of any other medicine you are using to see if it contains aspirin, ibuprofen, ketoprofen, or naproxen.
Do not drink alcohol while taking diclofenac. Alcohol can increase the risk of stomach bleeding caused by diclofenac.
Avoid exposure to sunlight or artificial UV rays (sunlamps or tanning beds). Diclofenac can make your skin more sensitive to sunlight and sunburn may result.