<prompt> Action of vincristine -Tubulin inhibitorAntimetaboliteAdenylate cyclase inhibitorAnti folate  <response>: Ans. is a i.e., Tubulin inhibitorVincristine Oncovino Alkaloid derived from Vinca rosae.o Vincristine belongs to the plant alkaloid group of anticancer.o Rapidly acting anticancero This class of drugs are also known as spindle poison,o These drugs bind to microtubular protein tubulino The drug-tubulin complex then attaches itself to microtubules and causes depolvmerization of microtubules.o Depolvmerization of microtubule causesMitotic arrest at metaphaseDissolution of mitotic spindleInterference with chromosome segregationo Useful for inducing remission in childhood ALL not useful in maintenance therapyo It can also be used for pediatric solid tumors Wilnvs tumor, neuroblastoma, rhabdomyosarcoma and lymphomas,o Prominent adverse effects-Peripheral neuropathy Alopecia SL4DHVincristine is a marrow sparing drug but some times it may cause myelosuppression which is very less than vinblastin.o Indications of vincristine-Hodgkins disease Wilmss tumour Carcinoma lungNon hodgkins disease Ewings sarcoma Myelomao Vinblastine and vinorelbine are other vinca alkaloids.o Vinblastines most important clinical use is the curative therapy of metastatic testicular tumor,o Vinblastine can cause bone marrow suppression in contrast with vincristin, alopecia, and nausea vomiting,o As they arrest mitosis, all vinca alkaloids act in M phase. 