Cephalosporins

The peri-operative and empiric workhorse. A single pre-incision dose within 60 minutes — cefotetan or cefoxitin alone, or cefazolin + metronidazole — covers the enteric flora for appendectomy, and no postoperative antibiotics are needed for uncomplicated disease (WSES 2020, Strong). For perforation with peritonitis, a third-generation cephalosporin (ceftriaxone, cefotaxime) + metronidazole covers aerobic gram-negatives plus anaerobes for a short (2–3-day) postoperative course in complicated disease (WSES 2025).

Cephalexin is the sourced first-line for mild nonpurulent cellulitis — 500 mg every 6 hours, for at least 5 days. The disorder-side reason is a coverage argument rather than a habit: mild nonpurulent cellulitis needs streptococcal and methicillin-sensitive S. aureus cover, and the chapter asks for "antibiotics effective against streptococcal species," with MSSA also considered. MRSA cover is for purulent infection or MRSA risk, so reaching for it in a simple case is overtreatment. When the patient is systemically unwell but has no MRSA risk, the escalation stays within the class: "intravenous cefazolin, then switch to oral cephalexin." On duration, two sourced figures differ by audience and should be given honestly: the clinical chapters say at least 5 days, extended if improvement does not occur, while NHS patient information describes antibiotic tablets "usually for a week" for mild cellulitis. The number that decides between them is the reassessment: improvement is expected within 48 hours. Generation-by-generation spectrum and cross-reactivity belong to the class page.

The empiric gram-negative and anaerobic biliary coverage when antibiotics are indicated — complicated cholecystitis, cholangitis, sepsis, and perioperative prophylaxis for early laparoscopy. TG18 regimens (as reported by J Clin Med 2023) pair a cephalosporin with metronidazole for mild-to-moderate community-acquired cholecystitis and use a third-generation cephalosporin (cefotaxime or ceftriaxone) ± an anaerobic agent for non-severe cholangitis; cefepime + vancomycin ± metronidazole, piperacillin-tazobactam or a carbapenem cover severe or healthcare-associated infection. Antibiotics are not for every uncomplicated case, and after cholecystectomy with adequate source control they are withdrawn within 24 h (≈ 4 days for complicated disease; 4–7 days after successful drainage for cholangitis). One irony: ceftriaxone itself causes biliary sludge that can mimic cholecystitis.

Ceftriaxone covers penicillin-susceptible streptococci with once-daily dosing that suits home OPAT, is preferred for HACEK and other gram-negatives because beta-lactamase production is common, and partners ampicillin against E. faecalis. Cefazolin is the MSSA alternative to nafcillin (both run 6 weeks). For dental prophylaxis, an oral cephalosporin or penicillin is preferred over clindamycin because of C. difficile risk.

The empiric backbone: ceftriaxone + vancomycin, fast — started for every suspected bacterial meningitis, before the LP if the patient is severely ill, because a 3–6 hour treatment delay is associated with increased mortality. Ceftriaxone (or cefotaxime) is also first-line for meningococcal disease; after neurosurgery or head trauma the regimen switches to vancomycin + ceftazidime or cefepime for MRSA and Pseudomonas coverage.

Part of empiric therapy (e.g., ceftriaxone with vancomycin); cefazolin is an alternative for susceptible staphylococci and, with cefuroxime, the surgical prophylaxis given 30 minutes before incision to prevent post-operative osteomyelitis.

The classic inpatient β-lactam backbone: third-generation ceftriaxone or cefotaxime paired with a macrolide (or doxycycline). IDSA’s CAP clinical pathway doses it for a hospitalized adult as ceftriaxone 1–2 g IV every 24 hours (2 g if over 80 kg, and 2 g in severe CAP) or cefotaxime 1–2 g IV every 8 hours, plus azithromycin 500 mg IV or PO every 24 hours — clarithromycin 500 mg every 12 hours, or doxycycline 100 mg every 12 hours when a macrolide is not tolerated or the QTc is prolonged; with benzylpenicillin, targeted therapy for S. pneumoniae. The anti-pseudomonal generations — cefepime, ceftazidime — cover HAP/VAP and P. aeruginosa.

Cefazolin before cesarean skin incision; cephalexin for mild wound infection or mastitis. StatPearls: "Weight-based IV cefazolin should be given within 60 minutes before the skin incision." WHO: "a single dose of first generation cephalosporin or penicillin should be used in preference to other classes of antibiotics." StatPearls: "In the absence of purulent drainage, a first-generation cephalosporin, eg, cephalexin, provides effective coverage."

Third-generation agents bring broad-spectrum, predominantly gram-negative activity with beta-lactamase stability — indicated in gram-negative sepsis and empiric therapy of serious infections (meningitis, pneumonia, GU, bone/joint) when the suspected source points their way.

Ceftriaxone is the backbone of both gonorrhea and pelvic inflammatory disease treatment — those are the two infections the first-line chip on this class refers to — and its dose is weight-dependent in two different places. The rule is an administration rule, and it holds wherever ceftriaxone is given in this treatment context: "Ceftriaxone 500 mg IM in a single dose" for persons weighing under 150 kg, and "1 g of ceftriaxone should be administered" for persons weighing 150 kg or more. Both the number and the weight threshold changed from older teaching, and both are tested. In the outpatient PID regimen it is 500 mg IM as a single dose, rising to 1 g for persons above 150 kg with documented gonorrhea. In parenteral PID regimen 1 it is 1 g intravenously every 24 hours. Other cephalosporins occupy specific niches rather than being interchangeable — cefoxitin and cefotetan in the parenteral pelvic inflammatory disease regimens, cefixime when ceftriaxone is unavailable, and ceftriaxone again as a penicillin-allergy option in primary and secondary syphilis. Those alternative regimens and their doses belong to the class page; what belongs here is that ceftriaxone is the backbone and that its dose is weight-dependent. Note what is no longer part of the gonorrhea regimen: routine azithromycin. Doxycycline is added only when chlamydia has not been excluded. Cephalosporin generations, spectrum and cross-reactivity belong to the class page.

The original β-lactams — bactericidal cell-wall inhibitors. The defining nursing job is screening for and recognizing allergy, from rash to anaphylaxis.

Powerful, broad-spectrum DNA-synthesis blockers — but a boxed warning for disabling tendon, nerve, and CNS effects means they’re reserved when alternatives exist.

Suppress viral replication rather than kill viruses outright. The nursing essentials: hydrate with acyclovir, start early (flu within 48 h), and remember most antivirals suppress — they don’t cure.

Powerful IV drugs for serious Gram-negative infection — but nephrotoxic and ototoxic. Levels matter.

Broad, generally safe protein-synthesis inhibitors — a penicillin-allergy alternative. Watch QT and CYP3A4.

Broad-spectrum 30S inhibitors. Generally avoided in pregnancy and in children 8 or younger (permanent tooth staining) unless the infection is serious — doxycycline is still first-line for Rocky Mountain spotted fever at any age — and kept apart from dairy/antacids.