These are antiparasite agents (the most familiar of which is called ivermectin) that are widely used against fleas and gut worms.

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Should Merck stop donating its drug, ivermectin, to potential victims of riverblindness?

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Relief from itchiness comes with the ivermectin -- even for someone who has lived with the disease for more than 50 years, he said.

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The side effects from the medicine can also be nasty: Ivermectin may cause fever, itching, skin rash, joint or muscle pain, rapid heartbeat, and painful, tender glands.

CNN: With river blindness, 'you never sleep'