The stability and the behavior of patent blue (Alphazurine 2G) dye in a vehicle such as lidocaine hydrochloride injection were studied with regard to medication orders which may be prepared by hospital pharmacists. The patent blue family of dyes are sulfonated diaminotriphenylmethane, vital, acid dyes which have been used as diagnostic aids in both lymphography and burn debridement. A literature review, including some toxicological information, is presented. The occurrence of the sodium salt form and the equilibrium solubility of the patent blue sample studied are reported. Some implications of patent blue injections include: Clinical literature reports of toxicities, the unapproved status of patent blue by the Food and Drug Administration, results of stability studies, and the formation of viscid, water-insoluble precipitates of patent blue in combination with lidocaine hydrochloride. The extemporaneous preparation and subsequent use of parenteral prescriptions of patent blue dye in vehicles containing lidocaine hydrochloride and methylparaben are not recommended.