Products that interfere with the enzymatic breakdown of the drug can significantly (and dangerously) increase blood levels of the drug. For example, the gastric acid-reducing drug, cimetidine (Tagamet), has this effect and can be a useful potentiator of fentanyl. One recent report has suggested that taking grapefruit juice ‘may result in a potentially dangerous increase in fentanyl plasma concentrations. This can, in turn, increase or prolong adverse drug effects and may cause potentially fatal respiratory depression’. See: https://bit.ly/2SnaePY
Marketed forms of fentanyl include ampules for intravenous administration (eg. a 10ml ampule contains 0.5 mg fentanyl) and skin patches with various delivery rates (eg. 0.1mg per hour). The analogue, carfentanil, is even more potent than fentanyl and is not marketed as a pharmaceutical product. Reports received by Exit suggest it can be illegally purchased at White House Market on the dark web (using Tor browser). See: https://bit.ly/33c8sU4
Commercial ampoule of Fentanyl Citrate 0.5mg in 10ml