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Column originally published May 29, 2018

Side Effect Of Singulair

Question: Our daughter has quite severe asthma. She gets a bad cough whenever her asthma flairs up. She has been treated with puffers. Last fall, our doctor suggested that we should give her a pill called Singulair every day. To our surprise, her asthma got much better after several weeks. Through the winter, I stopped this medicine partly because she was doing so well, and partly because I have read that it can cause side effects like mood swings. Our daughter didn’t have any side effect, but I was just worried. Lately, she is getting worse again. I am scared to start her back on Singulair. What should I do?


I am glad to hear that your daughter did well through the winter. It is always good to have some reprieve from a chronic condition like asthma. However, it is very common for those who have allergy and asthma to get worse in spring.

Allergy can affect different parts of the body. Those who have hay fever have allergies in their eyes and nose; they are usually sensitive to pollens from trees and flowers. They can have itchy eyes and itchy nose, as well as sneezing and running nose.

Asthma is an allergic condition in the lungs. When pollens land in the bronchial tubes, they trigger a series of chemical reactions with the production of leukotrienes. These leukotrienes cause swelling of the bronchial tubes, production of excessive mucus, and tightening of muscles around the bronchial tubes. They give rise to asthma symptoms: cough, chest congestion, difficulty breathing, or wheezing.

This is where Singulair comes in. It blocks the leukotrienes and prevents the symptoms of asthma. It is a preventative medicine; it doesn’t work right away. After daily use for one to two weeks, most children (and their parents) will notice that they are better, with less cough and chest congestion; they can run farther before getting out of breath. Many can reduce or stop the use of inhalers.

For those who have chronic asthma with year-round symptoms, they should use Singulair daily without stopping. I have some patients that have used it for well over ten years. For those who have symptoms mostly in spring or fall, they can start Singulair at least two weeks before the beginning of their allergy season, and continue it for several weeks after the expected season is over.

Singulair has been used in Canada for a long time. In recent years, there are reports of side effects in children and adults, including irritability, getting frustrated and angry easily, mood changes, bad dreams, and rarely, suicidal thoughts. If it is going to happen, these side effects usually appear within a few days after Singulair is started. We still don’t know the cause of these side effects, but they are quite uncommon.

For this reason, I only recommend Singulair for prevention of asthma, and not for hay fever type of allergy. There are several excellent over-the-counter long-acting antihistamines that can treat hay fever symptoms very effectively. I reserve Singulair for asthma because it is a more serious medical condition. Daily use of Singulair can reduce the severity of asthma, and may reduce the need of inhaled steroids.

If your daughter had used Singulair successfully last year, most likely it will still benefit her without any side effect. It is important to start Singulair as early as possible, preferably before the beginning of the allergy season. Monitor for any possible side effect. It is important to get her asthma under good control instead of worrying about possible side effects that may never occur.