Sinusitis as well as sinus infection is experienced regularly among people in my profession (commercial pilot) since the constantly changing air pressure (as well as desert dry air while flying) irritates the sinus mucosa membranes lining the cavities, which, in turn, produces more mucous (yuck). Problem is, while the bacteria population naturally present in such areas is naturally controlled by oxygen… nature's greatest bacteria killer, small areas within the cavities become sealed off, due to swelling, etc., and self-perpetuating bacteria growth… often amazingly productive, causes the infection.
Most of us here (I'm in the U.S.) agree that Augmentin, with an efficacy rate of above 94% seems to be the best antibiotic treatment even for chronic sinusitis. However, on the preventive side, use several times a day of any over the counter saline nasal sprays help keep the malady at bay since it prevent the drying of the mucosa and keeps the drainage going.
Some sinus infections are virally caused, in which case, all bets are off, especially in the use of antibiotics.
Hot, damp packs applied to the face and forehead seems to help those that are suffering, as well as keeping the humidity as high as possible.
Those experiencing chronic sinusitis may suffer for a couple of months, while acute sinusitis last maybe only 4 weeks. The usual Augmentin dosage is for 10 days and may be repeated for one more round if needed.
Personally, I'd keep the usage of codeine type pain relievers at a minimum, but I'm certainly no doctor.
If the symptoms persist, many have found relief in using Corticosteroids, which will relieve the swelling. I've used it once a day for maybe 30 days and while it does really help, I've noticed a minor loss of sense of smell.