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P A R T 2
Chemotherapeutic agents
be taken on an empty stomach to ensure adequate
absorption. Penicillins are excreted unchanged in the
urine, making renal function an important factor in
safe use of the drug. Penicillins enter breast milk and
can cause adverse reactions (see contraindications and
cautions).
Contraindications and cautions
These drugs are contraindicated in people with aller-
gies to penicillin or cephalosporins or other allergens.
Penicillin sensitivity tests are available if the person’s
history of allergy is unclear and a penicillin is the
drug of choice. Use with caution in people with renal
disease (lowered doses are necessary
because excretion
is reduced
). Although there are no adequate studies of
use during pregnancy, use in women who are pregnant
and in breastfeeding women should be limited to situa-
tions in which the mother clearly would benefit from the
drug,
because diarrhoea and superinfections may occur
in the infant
.
Perform culture and sensitivity tests
to ensure that
the causative organism is sensitive to the penicillin
selected for use.
With the emergence of many resist-
ant strains of bacteria, this has become increasingly
important.
Adverse effects
The major adverse effects of penicillin therapy involve
the GI tract. Common adverse effects include nausea,
vomiting, diarrhoea, abdominal pain, glossitis, sto-
matitis, gastritis, sore mouth and furry tongue. These
effects are primarily related to the loss of bacteria from
the normal flora and the subsequent opportunistic
infections that occur. Superinfections, including yeast
infections, are also very common and are again associ-
ated with the loss of bacteria from the normal flora. Pain
and inflammation at the injection site can occur with
injectable forms of the drugs. Hypersensitivity reactions
may include rash, fever, wheezing and, with repeated
exposure, anaphylaxis that can progress to anaphylactic
shock and death.
Clinically important drug–drug interactions
If penicillins and penicillinase-resistant antibiotics are
taken concurrently with tetracyclines, a decrease in the
effectiveness of the penicillins results. This combina-
tion should be avoided if at all possible, or the penicillin
doses should be raised, which could increase the occur-
rence of adverse effects.
In addition, when the parenteral forms of penicil-
lins and penicillinase-resistant drugs are administered
in combination with any of the parenteral aminoglyco-
sides, inactivation of the aminoglycosides occurs. These
combinations should also be avoided.
Prototype summary: Amoxycillin
Indications:
Treatment of infections caused by
susceptible strains of bacteria, postexposure
prophylaxis for anthrax, treatment of
Helicobacter
infections as part of combination therapy.
Actions:
Inhibits synthesis of the cell wall in
susceptible bacteria, causing cell death.
Pharmacokinetics:
Route Onset
Peak
Duration
Oral
Varies
1 hours
6–8 hours
T
1/2
:
1 to 1.4 hours; excreted unchanged in the urine.
Adverse effects:
Nausea, vomiting, diarrhoea,
glossitis, stomatitis, bone marrow suppression,
rash, fever, superinfections, lethargy.
Care considerations for
people receiving penicillins and
penicillinase-resistant antibiotics
Assessment: History and examination
■
■
Assess for
possible contraindications or cautions
:
known allergy to any cephalosporins, penicillins
or other allergens
because cross-sensitivity often
occurs
(obtain specific information about the
nature and occurrence of allergic reactions);
history of renal disease
that could interfere with
excretion of the drug
; and current pregnancy or
breastfeeding status.
■
■
Perform a physical assessment
to establish
baseline data for evaluating the effectiveness of
the drug and the occurrence of any adverse effects
associated with drug therapy.
■
■
Examine skin and mucous membranes for any
rashes or lesions and injection sites for abscess
formation
to provide a baseline for possible
adverse effects.
■
■
Perform culture and sensitivity tests at the site of
infection
to ensure that this is the drug of choice
for this person.
■
■
Note respiratory status
to provide a baseline for
the occurrence of hypersensitivity reactions.
■
■
Examine the abdomen
to monitor for adverse
effects.
Evaluate renal function test findings,
including BUN and creatinine clearance,
to assess
the status of renal functioning and to determine
any needed alteration in dose.
Implementation with rationale
■
■
Check culture and sensitivity reports
to ensure that
this is the drug of choice for this person.
