Imodium had shorter effect

I haven't heard of immodium changing their formulas. However, i've seen an array of choices they offer. Including one that helped with gass and bloating. Now, I guess it is possible, but usually they would change the packaging. Keep in mind that they're not like lemon, or orage juice where amounts/taste will vary. When it comes to medications the pharmacists are very precise. Have you checked the expiration date?

Also, I wouldn't put too much emphasis on when you have a bowl movement, unless it's an obvious redflag, because if here's something that needs to come out your body, it WILL come out, regardless of what you take. Remember, your body has all sorts of defense mechanisms, and evacuating waste is one of them.

A drug in one country will need to meet the needs of the admistration and in the US it is the FDA so the requirements of the FDA may differ to the Norway administration. Also what is legal in one country may not be legal in another. Medicine is a minefield. To sell medical products in any one country requires a license and each country requires their own. Obviously this depends if it is under license such as a newer drug but once that runs out it is a free for all. Have a look at the packaging and look to see if it is the same as another possibility is parallel import. There is very little consistency of supply in one country let alone another for example the prescription your doc gives you may not be what the pharmacist gives you for cost cutting reasons.