Taking Zofran (ondansetron) odt for nausea. Doc said I could double 4mg tablets. I took 2 tablets 4 hours ago is it okay take another dose?

Maybe. In general, zofran (ondansetron) is made for short-term usage, and if it has not gotten your symptoms under control yet, adding more is unlikely to help. If, however, it was helping and has worn off, taking one additional tablet would be okay. Again, in the short-term. Keep in mind zofran (ondansetron) is an opiate relative, which means if you have a drug or alcohol history or a family history, it is not your best choice.