Mezlocillin is a new broad-spectrum semisynthetic
penicillin that has shown encouraging in vitro activity against the infecting organisms most likely to cause mortality and morbidity in
cancer patients receiving
chemotherapy. The serum clearances and urine recoveries of
mezlocillin,
ampicillin, and
carbenicillin were compared after the
intravenous administration of single 3-g doses. The peak mean serum concentrations of
mezlocillin and
carbenicillin were 269 and 278 mug/ml, respectively, whereas the peak
ampicillin level was lower at 167 mug/ml. The terminal half-life of
mezlocillin, 66 min, was not significantly different from those of
ampicillin and carbencillin (63 and 77 min, respectively). Recoveries of
mezlocillin,
ampicillin, and
carbenicillin from urine over 6-h periods after
drug dosage were 45, 61, and 80%, respectively. A further study in 11
cancer patients examined serum maintenance levels of
mezlocillin when 3-g doses were given intravenously every 4 h for at least 7 consecutive days. After 3 days of
therapy, the mean serum concentrations were maintained above 50 mug/ml. Although therapeutic efficacy was not an objective of this study, all of three documented
bacterial infections were cured, and no serious toxicity was encountered.