Cefdinir is a cephalosporin (SEF a low spor in) antibiotic that is used to treat many different types of infections caused by bacteria. Cefdinir may also be used for purposes not listed in this medication guide. Cefdinir is an antibiotic in the cephalosporin drug class prescribed to treat infections, for example, middle ear, tonsillitis, strep throat, bronchitis, and sinusitis. Common side effects are nausea, abdominal pain, loose stools, and vaginitis. Dosage and pregnancy and breastfeeding safety information are included. Cephalosporin Antibiotics (Cephems): classification of cephalosporins by generation -- 1st generation, 2nd generation, 3rd generation, 4th generation; side effects, indications and uses, mode of action, spectrum of activity. Cefdinir, sold under the brand name Omnicef among others, is an antibiotic used to treat pneumonia, otitis media, strep throat, and cellulitis. It is a less preferred option for pneumonia, otitis media, and strep throat which may be used in those with a severe allergy to penicillin. It is taken by mouth. DESCRIPTION. Oral extended-spectrum, semisynthetic, third generation cephalosporin. It is not active against methicillin-resistant staphylococci or Pseudomonas aeruginosa. As your son has been given Cefdinir which is a Cephalosporin (Third Generation) and can cause such allergic reaction (cross reactivity). The allergic reaction keeps on worsening unless the offending drug is discontinued. What is Cefdinir? Cefdinir is an advanced semi-synthetic (when an original drug chemically modified to isolate the active ingredient), antimicrobial drug i.e. third generation cephalosporin drug which is isolated from the plant, bacterial sources (Cephalosporium acremonium). Cefdinir is an antibiotic prescribed to treat a wide range of bacterial infections, including certain types of pneumonia, sinusitis, bronchitis, strep throat, sore throat, middle-ear infections. Discovery. The aerobic mold which yielded cephalosporin was found in the sea near a sewage outfall in Su Siccu, by Cagliari harbour in Sardinia, by the Italian pharmacologist Giuseppe Brotzu in July 1945. Cefdinir Pharmacokinetics Absorption Bioavailability. 16–25%. 1 40 Peak plasma concentrations attained 2–4 hours after an oral dose. 1 23 27 28 40. Bioavailability of oral suspension is 120% of that reported with capsules. 1 40.