Action of vincristine -

Ans. is 'a' i.e., Tubulin inhibitorVincristine (Oncovin)o 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 (tubulin)o 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 therapy)o 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 Wilms's tumour Carcinoma lungNon hodgkin's disease Ewings sarcoma Myelomao Vinblastine and vinorelbine are other vinca alkaloids.o Vinblastine's 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.