<prompt> Which antiemetic drug selectively blocks levodopa induced vomiting without blocking its anti-Parkinsonian action?MetoclopramideCisaprideDomperidoneOndansetron  <response>: LevodopaLev alone- Is less potent- As peripheral dopamine decarboxylase effective than central.Therefore, efficacy of drug decreases. As L-DOPA - Dopamine conveed in periphery central - DA causes peripheral side effects D1 - Hypotension B1 - Arrhythmias a1 - Hypeension CTZ - Vomiting Antiemetic drugs: D2 antagonist : Metoclopramide Domperidone Cross BBB Can cause dystonia Do not cross BBB Do not cause dystonia DOC for levodopa induced vomiting 5HT3 5HT4 No other action As domperidone do not cross BBB, it blocks levodopa induced vomiting without blocking its anti - parkinsonism effect. 