The antimicrobial spectra, pharmacokinetics, tissue penetration, side effects, clinical trials and indications, dosage, and cost of
mezlocillin (
Mezlin) and
piperacillin (
Pipracil), two new semisynthetic
beta-lactam penicillins, are reviewed. Both
mezlocillin and
piperacillin are active against a wider range of bacteria than previously available
penicillins, but their spectra are not identical.
Piperacillin is more active than
mezlocillin against Pseudomonas aeruginosa; their activities against Klebsiella pneumoniae, Streptococcus faecalis, and Bacteroides fragilis are similar to one another. Neither
drug is absorbed orally; both are well absorbed (60-70%) after i.m. injection. Following i.v. infusion or injection, both drugs distribute rapidly (distribution half-life = 10-20 min); neither is
protein bound substantially. Both drugs are primarily excreted unchanged in the urine by glomerular filtration and tubular secretion. Elimination half-lives of both drugs are slightly prolonged in
renal-failure patients. However, the half-life of
mezlocillin in
renal failure is longer then the half-life of
piperacillin because of dose-dependent kinetics of
mezlocillin at low glomecular filtration rates.
Probenecid alters the disposition of both drugs. Both drugs are widely distributed throughout the body. Reported side effects are similar to those of other
penicillins.
Mezlocillin and
piperacillin may be used to treat susceptible organisms causing the following conditions: complicated and uncomplicated
urinary-tract infections,
septicemia, uncomplicated gonococcal
urethritis, and lower respiratory-tract, intra-abdominal, gynecologic, skin, and skin-structure
infections.
Piperacillin is also effective for bone and joint
infections. Dosages of both
antibiotics should be adjusted based on patients' clinical condition and renal status. Both agents are relatively expensive in comparison with older
penicillins and
cephalosporins; their daily costs are similar to
third-generation cephalosporins,
carbenicillin, and
ticarcillin. The potential benefits of
mezlocillin and
piperacillin are in their extended in vitro spectra of activity and minimal toxicities. More comparative clinical trials are needed to support any claims of clinical superiority of these drugs over older, less expensive regimens.