24 hours 
Inhaled steroids (like Qvar) go directly into the lungs and help to decrease the inflammation of airways that makes asthma attacks more likely. Because beclomethasone does not work quickly, it should not be used for treating an asthma attack. Rather, it is used twice a day in order to prevent asthma attacks. Maintaining long-term asthma control. QVAR ® is an asthma control medicine that should be taken every day to help keep asthma symptoms under control, even if a person is feeling better and not experiencing symptoms. Improvement may occur within 24 hours for some patients. Qvar is an asthma medication that belongs to a group of drugs called inhaled corticosteroids, or steroids for short. Inhaled steroids go directly into the lungs and help to decrease the inflammation of airways that makes asthma attacks more likely. Because Qvar does not work quickly, it should not be used for treating an asthma attack. Rather, it is used twice a day in order to prevent asthma attacks. Because Qvar is inhaled directly into the lungs, the rest of the body is exposed to lower steroid levels, compared to steroids taken by mouth. 1 Qvar comes in a metered-dose inhaler (called an MDI). 2  It is taken twice a day every day. 3  The medication is used to prevent asthma attacks, not to treat them. 4  You should test spray a Qvar inhaler before your first use of it or if you have not used it for more than ten days. 1 It is taken twice a day every day. 2  The medication is used to prevent asthma attacks, not to treat them. 3  You should test spray a Qvar inhaler before your first use of it or if you have not used it for more than ten days. 1 You should test spray a Qvar inhaler before your first use of it or if you have not used it for more than ten days. 2  To test spray the inhaler, spray it into the air twice by pressing the top of the canister.
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how long for qvar to work