Hypocarnitinemia Observed in an Infant Treated with Short-Term Administration of Antibiotic Containing Pivalic Acid.

Carnitine is a water-soluble amino acid derivative required for β-oxidation of long-chain fatty acids. In carnitine cycle abnormalities and low carnitine states, fatty acid β-oxidation is inhibited during fasting, resulting in hypoglycemia. Pivalic acid is a substance used in prodrugs to increase absorption of parent drugs, and antibiotics containing pivalic acid are frequently used as wide spectrum antibiotics for pediatric patients in Japan. Pivalic acid released after absorption is conjugated with free carnitine to form pivaloylcarnitine, which is then excreted in urine. As a consequence, long-term administration of pivalic acid containing antibiotics has been associated with depletion of free carnitine, inhibition of energy production and subsequent hypoglycemia. Here we report a case of a 23-month-old boy treated with an antibiotic containing pivalic acid for 3 days for upper respiratory tract infection. Laboratory data at referral indicated hypoglycemia, decreased free carnitine and elevated five-carbon acylcarnitine. Isomer separation confirmed the major component of increased five-carbon acylcarnitine to be pivaloylcarnitine, thereby excluding the possibility of a genetic metabolic disorder detected with similar acylcarnitine profile. The level of carnitine was normal when the antibiotic was not administered. Our case shows that the use of antibiotics containing pivalic acid in young children requires consideration of hypocarnitinemia, even with short-term administration.