Brief Answer:
Probably a stomach bug

Detailed Answer:
Hello,
Thank you for your query.

Prevacid is more potent that Zantac and doesn't cause loose stools.
Her symptoms indicate a possible stomach bug or food poisoning.

*does she have any other medical issues or take any medications?
*any change in diet the past week or unusual food intake?
*how long was she on Zantac?
*are the stools foul smelling? Does it have mucus?
*is she passing urine in normal amount and colour?
*how many episodes of loose stools and vomiting has she had so far?

I recommend :
-rest
-proper Hydration. Oral rehydration solutions /Gatorade (about 100ml after every loose stool or vomiting). She should sip on these in small quantities - a couple of table spoonful every 5 minutes.. The goal is for the urine to be light coloured and adequate
-avoid sugary, carbonated drinks, spicy, oily foods.
-rice, toast, applesauce, yogurt (with active cultures) are fine
-avoid milk. She can have black tea with lemon and honey. Helps soothe the intestine and reduce diarrhea.

If this Continues for more than 36 hrs and is severe OR if she is unable to drink/eat, and looks lethargic /sick, please take her to the ER.
A fever may ensue which can be treated with paracetamol. If fever persists more than 2 days, she needs to see a doctor then.

She may continue Prevacid (lansoprazole). If you have an antiemetic like ondasetron or do peridot, she may take that, if vomiting persists.
Remember to have smaller quantities of food and fluids until this resolves. Gulping fluid can trigger vomiting.

Hope this helps.
Please let me know if there is anything else I can help you with. Hope your mother feels better soon.

Wish you both good health.

Regards,
Dr. Shuba Hariprasad

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