Mammary Transfer of Loxoprofen (Loxonin^®) in Humans

Loxoprofen (Loxonin®) is a widely administered non-steroidal anti-inflammatory drug (NSAID) in Japan, with annual sales exceeding 50 billion Japanese yen. Although it is a very versatile drug and is often administered to breastfeeding women, the information available regarding its mammary gland transfer is inadequate.Therefore, in this study, we analyzed loxoprofen levels in the blood and milk of four breastfeeding women who received the drug for pain relief. These women visited the Obstetrics and Gynecology Department of Hanwa Sumiyoshi General Hospital for consultation or a cesarean section.One tablet of Loxonin® (loxoprofen 60 mg) was orally administered to each of the four women, and blood and milk samples were collected 0, 30, 90, 150 and 330 min after drug administration. Twenty microliters of ethanol was added to the blood and milk samples (10 μL), and the mixture was centrifuged at 12000 g for 15 min. The supernatant was analyzed by high-performance liquid chromatography (HPLC).Loxoprofen levels in blood peaked 90 min after its oral administration in all four patients, with the highest level being 4.5 μg/mL in patient II, whereas loxoprofen level in milk was below the detection limit (0.1 μg/mL) at all time points. Taken together, the data suggest low mammary gland transfer of loxoprofen, and thereby a low lactation risk.