Carnitine status and safety after administration of S-1108, a new oral cephem, to patients.

The metabolism and clinical safety of the pivalic acid-containing antibiotic S-1108, an orally active pro-drug cephalosporin, were investigated to assess the clinical effects, with special emphasis on the influence of carnitine consumption in 15 patients with various infectious diseases receiving S-1108 three times a day at a 300- or 600-mg total daily dose for 3 to 7 days. The free carnitine concentrations in plasma were greatly reduced to approximately 65% of pretreatment levels, and the plasma pivaloylcarnitine (the main metabolite of pivaloyloxymethyl ester) concentrations were increased during the 200-mg (three times a day) regimens but returned to the pretreatment levels within 3 to 5 days after the cessation of treatment. In three elderly patients with declining renal function (creatinine clearance rate, 31 to 50 ml/min), the acylcarnitine/free carnitine ratio increased from 0.1 to 0.4 up to 0.7 to 1.5 at day 5 during the 7-day treatment, showed a tendency to decrease, and then returned to the pretreatment ratio 4 days after discontinuation of the drug. The degree of free carnitine reduction and increase of the acylcarnitine/free carnitine ratio depended mostly on the dose and the duration of S-1108 treatment. The increased acylcarnitine/free carnitine ratio in elderly patients was due to reduction of the free carnitine concentration in plasma and mainly to the retardation of nontoxic pivaloylcarnitine excretion. This study indicated that there was a decrease in free carnitine levels in plasma, but there were no clinical symptoms or adverse effects associated with carnitine reduction in patients during the 7-day multiple administration of S-1108.