Brief Answer:
Zithromax is azithromycin an antibiotic .

Detailed Answer:
Hi

Thank you for asking HCM.

I have gone through your query. Zithromax is azithromycin an antibiotic. Vomiting and diarrhea can be due to gastroenteritis or food poisoning. Azithromycin can increase the gastric irritation than helping. O wouldn't recommend it unless there are features of infection.

Taking enough fluids and electrolytes is the main treatment of diarrhea and vomiting. You can take ORS, tender coconut water, black tea with lemon sugar and some salt.

Over the counter Proton pump inhibitors like omeprazole ( prilosec) will be helpful for decreasing gastric irritation also. Once nausea settles down you can take low irritating foods like rice porridge. Anti emetic like domperidone will be helpful for nausea but it is a prescription drug. As over the counter you can get dimehydrinate (dramamine) for nausea.

But if there is more vomiting and diarrhea followed by dehydration then intravenous fluid administration will be needed.

Hope this may help you. Let me know if anything not clear.
Thanks.

---