Follow the storage instructions on your tube and close it after taking out a tablet. An effervescent formulation is sensitive to moisture. A manufacturer may use a moisture-resistant tube, a cap containing a desiccant, or individual sealed blisters to help keep tablets dry. WHO tablet monograph
Pick a place you can use consistently
Read the temperature and storage wording before choosing a shelf. A dry cupboard away from steam may work better than the counter next to the kettle. If you carry the tube on a monsoon commute, keep it inside the dry part of your bag and check the cap when you get home. Use dry hands when taking out a tablet. Follow the pack’s instructions for any desiccant or packing insert and keep it away from children.
If the tube got wet
A few drops on the outside of a closed tube are a different situation from water inside the tube. Inspect the cap and seal. Set the pack aside and ask the manufacturer about the affected batch if tablets are visibly damp, stuck together, swollen or otherwise changed, or if the seal arrived damaged. Send a photo of the condition, batch and date. It is easier for the seller to identify the unit while you still have the carton and invoice.
Check any separate instructions for the period after opening. The batch and expiry guide helps you find the relevant date on the pack. Read the effervescent buying guide when choosing a pack size that fits the way you will store it.