**Question:** All of the following are Beta-lactamase inhibitors except: March 2005

A. Carbapenems
B. Ampicillin
C. Tazobactam
D. Nitrofurantoin

**Core Concept:** Beta-lactamase inhibitors are drugs that inhibit the bacterial enzyme beta-lactamase, which breaks down beta-lactam antibiotics like penicillins, cephalosporins, and carbapenems. Beta-lactamase inhibitors are essential in preserving the effectiveness of these antibiotics against pathogens that produce beta-lactamase.

**Why the Correct Answer is Right:** D. Nitrofurantoin is a urinary antiseptic and antiprotozoal agent used to treat urinary tract infections (UTIs). Although it is sometimes used to enhance the effectiveness of beta-lactam antibiotics in UTIs, nitrofurantoin is primarily an antiprotozoal agent and not a beta-lactamase inhibitor.

**Why Each Wrong Option is Incorrect:**

B. Ampicillin: A beta-lactam antibiotic used in the treatment of various infections. Although ampicillin is susceptible to beta-lactamase, it is not specifically an inhibitor of the enzyme.

C. Tazobactam: A beta-lactamase inhibitor that is commonly co-administered with cephalosporins to protect them from hydrolysis by beta-lactamase, making it a correct answer.

D. Nitrofurantoin: As mentioned earlier, nitrofurantoin is primarily an antiprotozoal agent and not a beta-lactamase inhibitor.

**Correct Answer:** D. Nitrofurantoin (1)