Zafirlukast is a type of medicine called a leukotriene receptor antagonist. This is used to control and prevent symptoms caused by asthma. Controlling the symptoms of asthma helps you maintain your normal activities. It will also cut down the time lost from school or work. 

Asthma occurs if your airways narrow and swell and may produce extra mucus. This can make breathing difficult and trigger coughing. For some people, asthma is a minor nuisance. For others, it can be a major problem that interferes, with daily activities. This condition may as well lead to a life-threatening asthma attack. The symptoms of asthma vary from person to person. You may have infrequent asthma attacks, have symptoms only at certain times, or have symptoms at all times. Asthma signs and symptoms may include:

• Chest tightness or pain
• Shortness of breath
• Trouble sleeping caused by shortness of breath, coughing or wheezing
• Wheezing when exhaling, which is a common sign of asthma in children
• Coughing or wheezing attacks that are worsened by a respiratory virus, such as a cold or the flu

Signs that your asthma is probably worsening include:

• Increasing difficulty breathing, as measured with a device used to check how well your lungs are working (peak flow meter)
• Asthma signs and symptoms that are more frequent and bothersome
• The need to use a quick-relief inhaler more often

For some people, asthma signs and symptoms flare up in certain situations:

• Occupational asthma – triggered by workplace irritants such as gases, chemical fumes, or dust
• Exercise-induced asthma – which may be worse when the air is cold and dry
• Allergy-induced asthma – triggered by airborne substances such as mold spores, pollen, cockroach waste, or particles of skin and dried saliva shed by pets 

The following are some factors that increase your chances of developing asthma:

• Being a smoker
• Being overweight
• Exposure to secondhand smoke
• Exposure to occupational triggers
• Having a blood relative with asthma
• Having another allergic condition such as atopic dermatitis or hay fever 

Asthma complications may include:

• Sick days from work or school during asthma flare-ups
• Signs and symptoms that interfere with sleep, work and other activities
• Emergency room visits and hospitalizations for severe asthma attacks
• A permanent narrowing of the tubes that carry air to and from your lungs which affects how well you can breathe
• Side effects from long-term use of some medications used to stabilize severe asthma

Severe asthma attacks can be life-threatening. Work with your doctor to determine what to do when your signs and symptoms worsen and when you need emergency treatment. Signs of an asthma emergency include:

• Shortness of breath when you are doing minimal physical activity
• Rapid worsening of shortness of breath or wheezing
• No improvement even after using a quick-relief inhaler

How does Zafirlukast work for asthma?

Leukotrienes act in many areas of the body. These are chemicals your body releases when you breathe in an allergen. These chemicals cause swelling in your lungs and tightening of the muscles around your airways. As a result, it causes asthma symptoms. 

Zafirlukast works by blocking the actions leukotrienes. This prevents the increased mucus production, inflammation, and narrowing of the airways that occurs in asthma. This helps prevent asthma attacks from occurring. 

How to use Zafirlukast?

This medication is taken without food usually two times a day or as directed by your doctor. Take Zafirlukast on an empty stomach at least one hour before or two hours after a meal/snack. Zafirlukast is taken by mouth with a full glass of water. The dosage is based on your medical condition and response to the treatment. 

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. Keep taking this medication even if you feel well. Do not increase your dose, use this drug more often, or stop using it without first consulting your doctor. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. If you missed a dose, call your doctor for instructions. Do not double the dose to make up for the missed dose. It may cause another complication or may worsen your current condition. 

What are the possible side effects of Zafirlukast?

Common side effects:

• Sore throat
• Headache
• Trouble sleeping
• Cold symptoms
• Nausea
• Malaise
• Diarrhea
• Stomach pain
• Dizziness
• Weakness
• Muscle pain

Tell your doctor right away if you have these rare but serious side effects:

• Tingling or swelling of the hands or feet
• Worsening shortness of breath
• Chest pain
• Signs of infection
• Easy bruising or bleeding
• Coughing up blood 
• Mental/mood changes 

Call for medical help if this occurs:

• Numbness or tingly feeling in your legs or arms
• Severe sinus pain or congestion 
• Depressed mood or unusual thoughts/behavior
• Liver problems
• High levels of certain white blood cells 

Precautions 

• This medicine should never be taken to treat an asthma attack. You should keep your normal reliever inhaler ready for this. Consult your doctor if you need to use your reliever more frequently than normal or if it becomes less effective at treating attacks.
• If you find that your asthma is improved after starting treatment with this medicine you should not stop taking any of your other medicines, in particular any corticosteroid inhalers or tablets. This medicine is not a substitute for corticosteroids. However, you may find that you need to use your reliever inhaler less frequently.
• This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor right away.
• The safety of this medicine for use during pregnancy has not been established. It should be used with caution during pregnancy, and only if the expected benefit to the mother is greater than any possible risks to the developing baby. Seek further medical advice from your doctor.
• This medicine passes into breast milk. This medicine should not be taken by women who are breastfeeding. Ask your doctor for further advice.