Can Flagyl be taken with pitavastatin?

There is a moderate interaction between both medications.

Moderate meaning:

Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.

Interactions between your drugs
Moderate
metroNIDAZOLE pitavastatin
Applies to: Flagyl (metronidazole), pitavastatin

Using metroNIDAZOLE together with pitavastatin may increase the risk of nerve damage, which is a potential side effect of both medications. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. Let your doctor know if you develop weakness, numbness, pain, burning, or tingling in your hands, feet, or limbs. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Interaction report: https://www.drugs.com/interactions-check.php?drug_list=1617-988,3167-0

Did you inform the Dr. who prescribed the antibiotic that the patient was on Pitavastatin?

If you did then the Dr. is aware of the potential interaction between both medications and he/she has outweighed that the benefits are greater than the risks, if you didn't inform the Dr., before the patient takes the antibiotic, as I mentioned contact the Dr. and double check.