Rise of testosterone, nortestosterone, and 17ß-estradiol concentrations in peripheral blood plasma of pigs after sublingual application in vivo

Application of endogenous anabolic steroids to meat producing animals is not allowed in the EU. In other countries application is practised due to a low oral activity based on an efficient first liver passage. This contrasts with pharmacological investigations where steroids were readily absorbed by the buccal and sublingual mucosa using absorption enhancers. An in vivo study was performed to clarify possible absorption after sublingual applications of one milligram portions of either testosterone (T), 17ß-estradiol (E), or nortestosterone (NT) in sesame oil to castrated male pigs (n = 5) without specific delivery systems during anaesthesia. Blood samples were drawn using jugular vein catheters for 15 min before and 3 h after application. Hormone concentrations were determined by Radioimmunoassay for T and E or Enzymeimmunoassay for NT. For all steroids a slight increase was measurable one minute after application. Maximal values for T, E, and NT were 2.5 ng/ml, 1.5 ng/ml and 4.2 ng/ml, respectively, and were observed after 10 min. The concentrations of the three steroids decreased slowly thereafter but were still significantly elevated 1–3 h after application. Oral absorption of steroids without enhancers should be considered in risk analysis.