Huh? Is that 250 mg of ivermectin in the arm? Is English your second language?
The “arm “ is the “study arm”, very common term to describe the cohorts that are separated for various study interventions. As a matter of fact, English is my second language, I babbled when I was an infant, but I gave it up when I grew up.
Here it is as used in the original report in JAMA network:”The ivermectin dosage for each patient in the intervention arm was calculated to the nearest 6-mg or 12-mg whole tablets (dosing table in the study protocol)”