Merlin should not be drunk after 1-2 months of opening, because drugs have a shelf life, which is different from the expiration date of the drug. It can be stored at room temperature below 25°C for 1-2 months to maintain the effectiveness of the medication. If it is longer than 1-2 months, it is not recommended to continue giving Merlin to children. Parents who open the mouth of Merlin only look at the expiration date of the drug, thinking that they can continue to take it as long as it is within the expiration date of the drug. The expiration date of the medication is when the medication is not opened and stored at room temperature. The cap of Merlin can easily cause bacterial contamination after the bottle is opened, which can affect the efficacy of the drug.