Like all medicines, Pranlukast can have side effects, but for most people, they are mild and go away as the body gets used to the drug. The most common issues reported are mild headaches or stomach upset, such as nausea or diarrhea.

Over the last 30 years, researchers have followed patients who take the medication for five years or more. These long-term studies have shown that it remains safe and effective over time. There is no evidence that the body becomes "used to" the drug in a way that makes it stop working. However, in very rare cases, some patients may experience more serious reactions, such as changes in liver enzymes or mood shifts. For this reason, regular follow-up appointments with a doctor are always recommended.