I'm not sure how long my LLMD is proposing to treat me. I started on a four day coctail of flagyl, biaxin, and omnicef. That was fun. now on omnicef which seems to be somewhat helping except the days with the herx which are terribel but a means to an end. Ten days after the start of treatment, researchers found that patients who stopped the drugs early were faring just as well as those who kept taking them; after a month, the vast majority of both. How long until the mucus color will clear up indicating that the drug is working? I have had some problems with drug resistance. I have had some problems with drug resistance. Submitted: 8 years ago. User Reviews for Omnicef. The following information is NOT intended to endorse drugs or recommend therapy. While these reviews might be helpful, they are not a substitute for the expertise, skill, knowledge and judgement of healthcare practitioners in patient care. User Reviews for Cefdinir to treat Sinusitis. Also known as: Omnicef, Omnicef Omni-Pac. The following information is NOT intended to endorse drugs or recommend therapy. Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Cirino on cefdinir how long does it take to work: Antibiotics such as Keflex can work in 7-10 days sometimes shorter- it is important to complete the course of therapy prescribed for you in order to completely eradicate the infection. Symptoms often go away prior to completion- but take them all to avoid a repeat. Hi -- FWIW -- when our son was suspected of Pandas in nov 2012, our ped prescribed a month of augmentin. She followed up with a 10 day run of cefindir. how long does it take omnicef to start working Generic Omnicef How To Buy Generic Omnicef. Generic Omnicef (Cefdinir) is an antibiotic medication used to treat internal bacterial infections. Common Questions and Answers about How long does it take for cefdinir to work omnicef ) I am impressed with this book because of the thoughtful and thorough discussion *explains* how the various herbs work , how to take them, what for , etc., giving *context* for each one.