Side Effects Of Montelukast

Like all medicines, montelukast can cause side effects, although not everyone gets them.

Common side effects

These common side effects of montelukast happen in more than 1 in 100 people. There are things you can do to help cope with them:

Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.

Serious side effects

Call your doctor or call 111 immediately if:

• you notice mood changes and you become anxious, depressed or aggressive
• you see things which are not there (hallucinations)
• you're finding it harder than usual to concentrate or remember things
• you have new problems with your sleep, or sleep problems that get worse, such as nightmares, sleepwalking or difficulty sleeping
• your speech changes or you start stuttering
• you have shaking or trembling in any part of your body
• you have an unusual or fast heartbeat
• you develop a combination of symptoms such as a flu-like illness, pins and needles or numbness of arms or legs, worsening of asthma symptoms, or a rash
• the whites of your eyes turn yellow, or your skin turns yellow although this may be less obvious on brown or black skin - this can be a sign of liver problems

It's important to tell your family or friends that you're taking montelukast, and that it may sometimes affect your mood, sleep or behaviour. This is so they can help you notice any changes.

Call 999 or go to A&E if:

Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.

Bring all the medicines you take with you.

Serious allergic reaction

It is possible to have a serious allergic reaction (anaphylaxis) to montelukast.

Call 999 now if:

• your lips, mouth, throat or tongue suddenly become swollen
• you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
• you suddenly become very confused, drowsy or dizzy
• someone faints and cannot be woken up
• a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

Other side effects

These are not all the side effects of montelukast. For a full list see the leaflet inside your medicines packet.

Reporting side effects

You can report any suspected side effect using the Yellow Card safety scheme.

Visit the Yellow Card website for more information about reporting side effects.

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