It does require a prescription. I have taken Duramectin paste--ivermectin 1.87% horse medicine available from any farm/feed store for many months. Most use the horse medicines as it is difficult to get a prescription from a doctor--and it would be for a very short time. The dosage is based on weight. To calculate: horse weight = human weight. The average dose is 12 mg., although it is argued it requires 16 mg to be effective. Take at bedtime once a day on an empty stomach.
For disseminated strongyloides, the CDC says take for 2 weeks after all symptoms are gone. You should probably take some very short breaks to rest the liver. (CDC.com)
I am now taking human ivermectin for the first time. I'm taking 12 mg tablet once a day which I purchased from India.