Can different brands of the same medication give different side effects?

[RoonilWazlib21]

I've been taking omeprazole for years and have always had the Almus brand with no issues at all. My last prescription I was given Teva brand and for the last 7 days since I started them I've had severe headaches, nausea, stomach pain and just a general feeling of being unwell. I'm also finding I'm having to top up with gaviscon to keep on top of the reflux which I haven't had to do for a long time.

Is this possible? Its the same medicine I just can't work out why the different brand is making me ill.

Different brands can vary by using different coatings and fillers. It is possible for these differences to cause side effects.

Anecdotally, yes. I take a daily medication and when I was researching it prior to starting it, I found loads of posts on forums, Reddit, etc from people saying that their doctor had switched them from brand name to generic and they were having awful side effects for the first time.

There was a big problem years ago when people with epilepsy were given generic sodium valproate instead of Epilim (original branded formulation) and their seizures became uncontrolled. Loads of people had to be put back on to Epilim after much campaigning.

Yes. I take Levothyroxine for an underactive thyroid, and i try to get the same brand each time because different brands sometimes give me side effects.

Thanks everyone. I phoned my GP who told me to take them back to pharmacy and ask them to change for my usual brand. Pharmacist happily did so and put a note on my file only to give me my usual brand in the future.