Buy Quality Pure Fentanyl Powder Online is a potent, synthetic opioid pain medication with a rapid onset and short duration of action. It is a strong agonist at the μ-opioid receptors.Fentanyl Powder (also known as fentanil) is a potent, synthetic opioid pain medication with a rapid onset and short duration of action. It is a strong agonist at the μ-opioid receptors. Fentanyl is estimated to be between 50 and 100 times as potent as morphine.