**Question:** All are true about cephalosporins, except:

A. Cephalosporins are beta-lactam antibiotics.
B. They are bacteriostatic agents.
C. They have a narrow therapeutic index.
D. They are usually administered intravenously.

**Core Concept:** Cephalosporins are a class of beta-lactam antibiotics. They inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), which leads to bacterial cell wall weakening and eventually cell death. Cephalosporins are bactericidal agents, not bacteriostatic. They have a relatively wide therapeutic index and can be administered orally or intravenously.

**Why the Correct Answer is Right:** Option B is incorrect because cephalosporins are bactericidal, not bacteriostatic agents. Bacteriostatic antibiotics inhibit bacterial growth without killing the bacteria, which allows the bacteria to recover upon discontinuation of the drug. In contrast, cephalosporins kill bacteria by causing their lysis (cell rupture) upon binding to PBPs and inhibiting cell wall synthesis.

**Why Each Wrong Option is Incorrect:**

**Option A:** Cephalosporins are indeed beta-lactam antibiotics, which makes this statement partially true. However, the core concept is that they are bactericidal, not bacteriostatic.

**Option C:** Cephalosporins have a relatively wide therapeutic index, meaning they can be used within a broader concentration range without causing significant toxicity to the patient. This statement is incorrect because a narrow therapeutic index indicates drugs with a small margin between therapeutic and toxic doses, which makes them more susceptible to inter-patient variability in pharmacokinetics and pharmacodynamics. Cephalosporins have a broad spectrum of activity against Gram-positive and Gram-negative bacteria, but they generally have a wide therapeutic index.

**Option D:** Cephalosporins can be administered orally or intravenously, which makes this statement partially true. However, cephalosporins can also be administered parenterally (intravenously, intramuscularly, or subcutaneously) for optimal absorption and therapeutic efficacy.

**Core Concept:** Cephalosporins are a class of antibiotics effective against both Gram-positive and Gram-negative bacteria due to their ability to inhibit bacterial cell wall synthesis. They are bactericidal and have a relatively wide spectrum of activity. Cephalosporins can be administered orally, parenterally, or topically for various clinical indications. The choice of administration route depends on factors such as patient condition, drug availability, and clinical need.