Precautions and Warnings With Montelukast

Educating yourself on precautions and warnings with montelukast before taking it can help ensure that treatment with the drug is successful. People with liver disease (including liver failure) or phenylketonuria should be monitored carefully when taking the drug. Precautions and warnings with montelukast also apply to people who are taking an oral steroid or who are allergic to any components of the medication.

Montelukast: What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking montelukast sodium (Singulair®) if you have:
  • Phenylketonuria
  • Liver disease, such as liver failure or cirrhosis
  • Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
Make sure to tell your healthcare provider about all of the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Precautions and Warnings With Montelukast

Warnings and precautions to be aware of prior to taking montelukast include the following:
  • The medication is not a fast-acting asthma medication and cannot replace fast-acting rescue inhalers. Do not use montelukast to treat an asthma attack. Anyone taking the drug for asthma should also have a rescue asthma medication available at all times. Let your healthcare provider know if you need to use your rescue inhaler more frequently than usual, as this may be a sign of worsening asthma.
  • Some people who were taking an oral or inhaled steroid may be able to decrease or stop this medication when starting montelukast. Your healthcare provider should decrease your dose of the steroid medication slowly. Stopping an oral or inhaled steroid too quickly can be dangerous.


  • People who have a sensitivity to aspirin should continue to avoid aspirin and other nonsteroidal anti-inflammatory medications while taking montelukast. This is because montelukast may not stop an asthma attack caused by aspirin in people with aspirin sensitivity.
  • There have been reports of behavior and mood changes in people taking montelukast. Contact your healthcare provider right away if you or your child experiences any of the following symptoms during treatment:
  • People who take this medicine may develop an increase in a certain type of white blood cells (known as eosinophils) and inflammation of the blood vessels throughout the body. This reaction is most likely to occur in people who are stopping a steroid medicine. Contact your healthcare provider if you experience any of the following possible symptoms of this problem:
    • Tingling, numbness, or "pins and needles" feelings in the arms or legs
    • Flu-like symptoms
    • Rash
    • Severe pain or swelling of the sinuses. 


  • Chewable montelukast tablets (but not regular montelukast tablets) contain phenylalanine. This is important information for people with phenylketonuria, who must limit their phenylalanine intake.
  • In rare cases, montelukast can cause liver damage. If you have liver disease, this medication may not be the best choice for you.
  • Montelukast can interact with other medications (see Drug Interactions With Montelukast).
  • Montelukast is considered a pregnancy Category B medication. This means that it is probably safe for use during pregnancy, although the full risks are not known. Talk to your healthcare provider about the risks and benefits of taking the drug while pregnant (see Singulair and Pregnancy).
  • It is not known if montelukast passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Singulair and Breastfeeding).
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Montelukast Sodium

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