98
P A R T 2
Chemotherapeutic agents
Imipenem-cilastatin is a combination of imipenem,
which interferes with cell wall synthesis and causes
bacterial cell death, and cilastin, which inactivates the
imipenem and leads to increased urinary excretion of
the drug and decreased renal toxicity. It can be given IM
or IV and is approved for use in children.
Meropenem is given IV every 8 hours by either bolus
over 5 minutes or IV infusion over 15–30 minutes.
Contraindications and cautions
Carbapenems are contraindicated in the following con-
ditions: known allergy to any of the carbapenems or
beta-lactams
;
seizure disorders,
which could be exacer-
bated by the drug
; meningitis,
because safety in people
with meningitis has not been established
; breastfeed-
ing,
because it is not known whether these drugs enter
breast milk, but potentially they could cause serious
effects in the infant.
Use caution during pregnancy
because carbapenems
are used to treat only severe infections, and the benefits
of the drug must be carefully weighed against potential
adverse effects on the fetus.
Test urine function regu-
larly when these drugs are used
because they depend on
the kidney for excretion and are toxic to the kidney.
Ertapenem is not recommended for use in people
younger than 18 years of age.
Adverse effects
Toxic effects on the GI tract can limit the use of carb
apenems in some people. Pseudomembranous colitis,
Clostridium difficile
diarrhoea and nausea and vomiting
can lead to serious dehydration and electrolyte imbal-
ances, as well as to new serious infections.
Superinfections can occur with any of the carb
apenems. Closely monitor to deal with the new infection
before it becomes overwhelming.
CNS effects can include headache, dizziness and
altered mental state. Seizures have been reported when
carbapenems are combined with other drugs. Monitor
people to provide safety measures if any of these occur.
TABLE 9.2
DRUGS IN FOCUS Carbapenems
Drug name
Dosage/route
Usual indications
doripenem (Doribax)
500 mg IV, over 1 hour every 8 hour for
5–14 days
Treatment of complicated intraabdominal
infections or complicated UTIs, including
pyelonephritis, caused by susceptible
bacteria
ertapenem (Invanz)
1 g/day IV or IM for 5–14 days
Treatment of community acquired
pneumonia, complicated GU infections,
acute pelvic infections, complicated
intra-abdominal infections, skin and skin
structure infections
imipenem-cilastatin
(Primaxin)
250–500 mg IV q 6–8 hours or 500–750 mg
IM q 12 hours
Paediatric: <40 kg and >3 months:
15 mg/kg/day IV q 6 hours
Treatment of serious respiratory, intra-
abdominal, urinary tract, gynaecological,
bone and joint, skin and skin structure
infections; septicaemia, endocarditis,
bone and joint infections, and
polymicrobic infections
meropenem (Merrem I.V.)
500 mg–1 g IV, q 8 hours
Treatment of respiratory tract infection,
complicated urinary tract infection,
febrile neutropenia, intra-abdominal and
gynaecological infections, complicated
skin infections, meningitis, septicaemia
where there is resistance to commonly
used antibiotics
Prototype summary: Ertapenem
Indications:
Treatment of community-acquired
pneumonia, complicated GU infections,
complicated intraabdominal infections, skin and
skin structure infections, and acute pelvic infections
caused by susceptible bacteria.
Actions:
Inhibits protein synthesis in susceptible
strains of gram-negative bacteria, disrupting
functional integrity of the cell membrane and
causing cell death.
Pharmacokinetics:
Route
Onset
Peak
IM, IV
Rapid
30–120 minutes
T
1/2
:
4 hours; excreted unchanged in the urine.
Adverse effects:
Headache, dizziness, nausea,
vomiting, pseudomembranous colitis, rash, pain at
injection site.
