In acute vomiting, when even a sip of water dont stay in stomach, this medicine helped magically several times:
This is sold in allopathic shops. This seems to be an equivalent to a branded medicine, Emetrol. Its primary content is Phos acid, which seems to improve digestion instantly.
The description for this medicine says: "For relief of nausea due to upset stomach from intestinal flu and food or drink indiscretions. Safe for children with flu or fever"
For general nausea and vomitting: 
 Dosage  Medicine     Note
 1st Medicine  Ars Alb 30     helps to neutralize toxin           
 2nd Medicine  Ipecac 30 in wet dose, every 15 minutes in wet dose, every 15 minutes
How often to repeat: 1st Medicine, only once, but 2nd medicine, every 15 mintes
How long to take: Slow down dose, say every 1 hour, 2 hours, as soon as improvement is noticed.
Other potential benefit from this protocol: