What does 'long a standard treatment' mean?

[Infin1ty]

Hello everyone,

I'd like to know what 'long a standard treatment' mean and if there is any mistake in the sentence below:

A recent study has found that amoxicillin, long a standard treatment for ear
infections, is about as effective as newer,more expensive antibiotics and
causes fewer side effects.

Thank you and wish you a nice weekend! :)
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Please feel free to correct me if you find any mistakes in my posts.

[Jamie (K)]

There's no mistake. It means "which has been a standard treatment for ear infections for a long time". From the length of my explanation, you can see why we shorten it.

[Infin1ty]

Thank you very much, Jamie.
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Please feel free to correct me if you find any mistakes in my posts.