Answer: B. Clavulanic acid

Explanation: Clavulanic acid irreversibly inhibits many β-lactamases, protecting companion antibiotics.

Answer: C. Inhibition of DNA synthesis by interacting with topoisomerase

Explanation: Ciprofloxacin targets DNA gyrase and topoisomerase IV, blocking DNA replication.

Answer: B. Anthracene nucleus fused to cyclohexane ring that is subsequently connected with amino sugar via glycosidic linkage

Explanation: Doxorubicin antibiotics feature an anthracycline core (anthracene).

Answer: B. Gentamicin

Explanation: Gentamicin lacks efficacy against Mycobacterium tuberculosis and is not used in TB therapy.

Answer: C. They are administered in a 5:1 dose ratio for synergy

Explanation: Cotrimoxazole uses a 5:1 trimethoprim:sulfamethoxazole ratio for optimal synergism.

Answer: A. Mefloquine

Explanation: Mefloquine is the 4-aminoquinoline with two 2′,8′-CF₃ substituents marketed as a racemate.

Answer: B. Polyenes: Fungi

Explanation: Polyenic antibiotics (e.g., amphotericin) are produced by fungal species, not bacteria.

Answer: D. Cycloserine

Explanation: Cycloserine dimerizes to a diketopiperazine in aqueous solution.

Answer: B. Inhibition of gene transcription of interleukins

Explanation: Cyclosporine binds cyclophilin and inhibits calcineurin, blocking IL-2 transcription.

Answer: A. Rifampin

Explanation: Ansamycins are macrocyclic antibiotics with an aliphatic “ansa” bridge; rifampin is the prototypical ansamycin.

Answer: A. Fluoroquinolones

Explanation: Fluoroquinolones (e.g., ciprofloxacin) are implicated in Achilles tendon rupture; other classes are not.

Answer: C. Piperacillin

Explanation: Piperacillin is a ureidopenicillin, not a carbapenem; thienamycin, imipenem, meropenem are carbapenems.

Answer: C. Carbenicillin

Explanation: Carbenicillin efficacy increases in acidic urine (pH 5–6), optimizing urinary tract infection treatment.

Answer: A. EGFR/HER2 inhibitor

Explanation: Trastuzumab is a monoclonal antibody targeting the HER2 receptor (ErbB2) on tumor cells.

Answer: B. Tacrolimus

Explanation: Everolimus, temsirolimus, and sirolimus directly inhibit mTOR; tacrolimus is a calcineurin inhibitor, not mTOR-targeted.

Answer: D. Peroxide bridge

Explanation: Artemisinin’s antimalarial activity derives from its endoperoxide bridge that generates free radicals inside parasites.

Answer: C. Rizatriptan

Explanation: Most triptans bear sulfonamide; rizatriptan lacks a sulfonamide moiety in its structure.

Answer: A. Cefazolin

Explanation: Cefazolin uniquely contains a 5-thio-1,2,3,4-tetrazole side chain linked by a methylene bridge.

Answer: C. Neomycin

Explanation: Neomycin is poorly absorbed systemically and is used topically, unlike netilmicin or sisomicin.

Answer: B. Protease inhibitors - Indinavir

Explanation: Indinavir is an HIV protease inhibitor; NRTIs include zidovudine, lamivudine, not ritonavir.