I'm a medical marijuana patient and my family doctor prescibed me an antibiotic called Flagyl can I still use both at same time?

With caution. Altho my research did not produce any specific interactions between cannabis & flagyl, preceed with caution since Flagyl can interact with many medications as well as with alcohol; so no alcohol (caution even with alcohol-containing mouthwash or otc cold meds) for at least a week after completing the flagyl. If you experience nausea/vomiting, notify your doc for possible alternative.
Flagyl and thc. Medications are often metabolized in the liver by enzymes called cyp 450. Data on the effects of Metronidazole (flagyl) on specific pathways of drug metabolism are limited but most likely on called cyp3a. Marijuana one ingredient called cbd most potently inhibited catalytic activity of human cyp3a enzymes, especially cyp3a4 and cyp3a5. So Flagyl and marijuana most likely interfere with each other.