All these drugs work as microtubule inhibitors except which?

• A. Colchicine
• B. Griseofulvin
• C. Mebendazole
• D. Allopurinol

Answer: (D)

Drugs that interfere with microtubule dynamics disrupt tubulin polymerization or spindle function, which blocks cell division or parasite replication. Colchicine binds tubulin and prevents its polymerization, stopping mitosis. Griseofulvin binds fungal microtubules and disrupts mitotic spindle in fungi. Mebendazole binds parasite tubulin and inhibits microtubule formation, impairing essential processes in worms. Allopurinol, on the other hand, targets purine metabolism by inhibiting xanthine oxidase to reduce uric acid production; it does not affect microtubules. So Allopurinol is not a microtubule inhibitor.