Q- Which of the following medications has the narrowest margin of safety due to a small difference between its therapeutic and toxic doses?
A- Alprazolam
B- Amantadine
C- Lithium
D- Simvastatin
C- Lithium- Serum levels of lithium must be monitored regularly to avoid toxicity, which can lead to serious neurologic, renal, and cardiac complications. The other drugs listed have wider therapeutic windows, making them safer.
Q- Which one of the following chemotherapeutic agents acts by binding to tubulin and disturbing microtubule polymerization?
A- Cyclophosphamide
B- Doxorubicin
C- Paclitaxel
D- Vincristine
D-Vincristine- It is a vinca alkaloid that binds to tubulin and prevents the polymerization of microtubules, leading to inhibition of mitotic spindle formation and arresting the cell cycle in metaphase. Cyclophosphamide is an alkylating agent. Doxorubicin intercalates DNA and inhibits topoisomerase ll. Paclitaxel stabilizes microtubules and prevents their disassembly.
Q- Which of the following medications is considered the most effective chronic treatment for both rheumatoid arthritis and choriocarcinoma?
A- Hydroxychloroquine
B- Methotrexate
C- Sulfasalazine
D- Thalidomide
B-Methotrexate- It is a folate antagonist that inhibits dihydrofolate reductase, impairing DNA synthesis. It is widely used as a first-line disease-modifying antirheumatic drug (DMARD) in rheumatoid arthritis and is also the drug of choice for choriocarcinoma, a highly chemo-sensitive tumor.
