Products that interfere with the enzymatic breakdown of the drug can significantly (and dangerously) increase blood levels of the drug. For example, the taking of 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
Marketed forms of fentanyl include ampules for intravenous administration (eg a 10ml ampule containing 0.5 mg fentanyl) and skin patches with various delivery rates (eg 0.1mg in an hour).
Fig 10.4 Commercial ampoule of Fentanyl Citrate 0.5mg in 10ml
The analogue carfentanil is even more potent than fentanyl and is not marketed as a pharmaceutical product. It is only available illegally.
