It is very important that your doctor check the progress of you or your child at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.
You or your child may be taking other medicines for asthma along with zafirlukast. Do not stop taking or reduce the dose of the other medicines, even if your asthma seems better, unless you are told to do so by your doctor.
Check with your doctor if your or your child's symptoms do not improve or if your asthma gets worse.
Stop using this medicine and check with your doctor right away if you or your child have pain or tenderness in the upper stomach; pale stools; dark urine; loss of appetite; nausea; unusual tiredness or weakness; or yellow eyes or skin. These could be symptoms of a serious liver problem.
This medicine may cause a rare blood condition called Churg-Strauss syndrome. This usually occurs in patients who have asthma or are taking oral steroid medicines that is being stopped or the dose is being reduced or lowered. Tell your doctor right away if you or your child have the following symptoms: a feeling of pins and needles, flu-like symptoms, numbness of the arms or legs, rash, or pain and swelling of the sinuses.
This medicine may cause some people to be agitated, disoriented, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed and have problems with sleep. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.