Can i take tums with simithicone that expired 5 months ago? having bad symptoms but cannot but new until the store opens?

The "use by" or expiration date of these products is the last date the manufacturer assures full potency. This does not turn toxic at that point. You can use it as needed but it may not be as helpful. I would in that setting.

Yes, in this setting it is likely that it would be OK to take it. The medication may be less potent, but it is not likely to cause you any ill effects because of the expiration date. You should still replace it when you can. Good luck.