I have a sinus infection and my dentist is out of town. I am taking Keflex prescribed by my regular doctor. I started yesterday - how long does this take to affect the infection. Thank you.

It may sometimes take 24 to 36 hours before the benefits of your antibiotics are felt, depending on the dose you take. If you can, you should try to contact your out of town dentist (cell phone, other emergency number) to make the sure the dose you're taking will be effective.

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