Joint pains, muscle aches, and muscle cramps are some less common side effects of Singulair
The Merck company, that makes Singulair has a website, that includes potential bad side effects. Their webpage can be found at:
http://www.singulair.com/montelukast_sodium/singulair/hcp/product_highlights/safety/index.jsp
Also, your pharmacist should have this information, and it should be in your paper "package insert". Read especially the section below about "Additional safety experience":
"Most frequently reported adverse experiences occurring more often than with placebo, regardless of causality assessment:
In adults and adolescents 15 years and older:
In children 2 to 14 years of age:
The safety profile in pediatric patients 6 to 14 years of age was generally similar to placebo and the adult safety profile
The safety profile in patients 2 to 5 years of age was similar to that in patients 6 to 14 years of age
The most frequently reported adverse events in pediatric patients, regardless of causality assessment, included pharyngitis, cough, abdominal pain, diarrhea, influenza, and fever
Additional safety experience:
In rare cases, patients on therapy with SINGULAIR may present with systemic eosinophilia, sometimes presenting with clinical features of vasculitis consistent with Churg-Strauss syndrome, a condition which is often treated with systemic corticosteroid therapy. A causal association between SINGULAIR and these underlying conditions has not been established
SINGULAIR is indicated for the prophylaxis and chronic treatment of asthma in patients aged 2 years and older.SINGULAIR should not be used as rescue medication to treat acute asthma episodes. Patients should be advised to have appropriate rescue medication available.Use of SINGULAIR may not eliminate the need for inhaled or systemic corticosteroids. Patients should not decrease the dose or stop taking any other anti-asthma medications unless instructed by a physician.Safety and effectiveness of SINGULAIR in patients younger than 2 years have not been established.
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This site is intended only for residents of the United States, its territories, and Puerto Rico.SINGULAIR is a registered trademark of Merck & Co., Inc.
20207170(1)-10/02-SNG"
Hope this helps. The LUNG LINE nurses can translate the medical language into plain English, for you.