Montelukast is a type of medication called a leukotrine inhibitor. This medication works to prevent asthmatic responses to allergens, which are substances that provoke allergic reactions. Leukotrine inhibitors are effective medications but can produce some side effects. The most common montelukast side effects can include headache, stomach pain, indigestion, and fatigue. In addition, the drug can occasionally cause marked changes in mental health.
Leukotrines are molecules that act as chemical signals in certain parts of the body. One of the primary functions of these molecules is to trigger contractions in the smooth muscles that line the trachea, or airway. In a respiratory allergic response, such as when an allergic person breathes in pollen, the contact with the allergen causes leukotrines to be over-produced in the smooth muscle. This can cause stronger, more rapid contractions, and symptoms such as inflammation and increased mucus production. Leukotrine inhibitors such as montelukast work by preventing leukotrine molecules from binding to the cell receptors that trigger allergic asthma symptoms.
Many of the most common montelukast side effects occur because leukotrines have other functions in the body in addition to their role in smooth tracheal muscle. Most people who take the drug will experience at least one of the following side effects: headache, toothache, dizziness, tiredness, nasal congestion, heartburn or indigestion, nausea or diarrhea, stomach pain, or a rash. These side effects are usually temporary, and are mild.
Ironically, some of the most serious of the montelukast side effects are signs of an allergic reaction to the drug. These include difficulty swallowing or breathing, swelling in certain areas of the body, rash, and itching. Some report flu-like symptoms, such as a hoarse throat and fever. An allergic reaction can also cause sinus pain and swelling, and numbness or pins and needles in the legs or arms, or a worsening of asthma symptoms. An overdose of the drug can cause headache and vomiting, or agitation and restlessness.
Another category of potentially severe montelukast side effects are changes to mental health. Possible changes include aggressive behavior, irritability, anxiety, and depression. Some patients may experience bouts of insomnia, hallucinations, and suicidal behavior as well. This means that for someone taking this drug, there is a small risk that mental health changes could increase the risk of a suicide attempt. These side effects are rare, but it is important to be aware that they can occur.
In some cases, drug interactions can cause additional montelukast side effects. While it is always a good idea to check with a doctor before taking any drug, including over-the-counter medications and supplements, there are some drugs that are known to cause specific side effects when taken with montelukast. These include the barbiturate phenobarbital and the antibiotic rifampin.