How long does it take for amoxicillin to start working?

she has a chronic sinus infection will this help?

I, personally and with my kids, have had no luck with amoxicillin for sinus infections. For one, amoxicillin works best on aerobic bacteria and sinus infections are usually caused by anaerobic bacterias. I dont know why Drs always want to prescribe amoxicillin as first line. I refuse it with my kids because it never works for them or if it does, as soon as they come off, the symptoms come right back. I think Augmentin works better. Augmentin is similar to amoxicillin but has a substance that breaks down the cell membrane of an anaerobic bacteria and allows the antibiotic to work better. If it has been a few days and there is no improvement, I would notify the Dr that it is not working.

she takes high blood pressure medicine she is 82 years old.

Even so, I think she would be better off with Augmentin. It shouldnt have any negative effects taking it with blood pressure meds or have a negative effect on her blood pressure. Sorry for jumping to the conclusion she was your child! It is just that amoxicillin is so often prescribed to kids with infections but my answer is the same for anyone.

Augmentin IS amoxicillin, it's just a specific trade name for it.

Augmentin is Amoxicillin + clavulanic acid.

(From Wikipedia) This combination results in an antibiotic with an increased spectrum of action and restored efficacy against amoxicillin-resistant bacteria.

I'm very prone to getting sinus infection. VERY prone and they never go away on their own. I end up with week long migraines and the sweats until I get antibiotics for it.
amoxicillin ALWAYS works for me and symptoms ease right up within 24 hours.

Happened about 5 times so far this year, this time my lymph node on my neck grew like I had a twin - yay for me!