I hate it when I take a pill and then get some weird symptom, like I don't know if it's a side effect or just a cold coming on. Makes me nervous too, especially at night. (typically it happens on a holiday weekend so I can't call the doc for four days

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Like all NSAIDs, Doan's can be hard on the stomach. Doan's isn't any more effective for back pain than any other OTC NSAID. [url]http://www.ftc.gov/opa/1999/05/doans.shtm[/url]
So if you're taking it specifically for back pain you may want to consider a switch to a newer, more tummy friendly NSAID.