The FDA does not “approve” drugs. The FDA licenses drugs.
Ivermectin is a licensed drug. There are coupons on GoodRx for it.
The FDA can and does list “indications” for licensed drugs, and they would LIKE to have the authority to restrict use to “indications”, such as “ivermectin is INDICATED for treatment of ascariasis” - but they have no such authority now,
So, pharmacists are asking for something that does not exist under US law, which is FDA permission to fill a prescription for a licensed drug,
In this case UK pharmacists...different rules/laws across the pond.