Zofran dosage and timing

How often are people taking zofran? My dr is concerned about heart side effects. I have no underlying heart issues, but those side effects of long term zofran use are a concern. I haven’t seen a lot on this forum for zofran side effects other than constipation.

I just started 4mg, taken once per week, the morning after my shot (which is taken the night before). It’s been working fine, but I’m about to move up in dosage and wondering if taking 8mg in one day will be bad. Also wondering what others do?

Usually nausea is rough the day after injection, then mild but fine to work etc on days after.

My SW is 160, GW is 120, CW is 145. (5’1”)