C H A P T E R 1 0
Antiviral agents
131
There are no adequate studies in pregnancy and breast-
feeding, so oseltamivir should be used during pregnancy
and breastfeeding only if the benefits clearly outweigh
the risks to the fetus or neonate.
Women of childbearing age should be advised to use
barrier contraceptives if they are taking ribavirin. The
drug has been associated with serious fetal effects.
Because of the renal excretion, zanamivir must be
used cautiously in people with any renal impairment.
It should be used during pregnancy and breastfeeding
only if the benefits clearly outweigh the risks to the fetus
or neonate.
People with renal dysfunction who are taking
oseltamivir require reduced doses and close monitoring
to avoid altered metabolism and excretion of the drug
.
There are no adequate studies in pregnancy and breast-
feeding, so oseltamivir should be used during pregnancy
and breastfeeding only if the benefits clearly outweigh
the risks to the fetus or neonate.
Women of childbearing age should be advised to use
barrier contraceptives if they are taking ribavirin. The
drug has been associated with serious fetal effects.
Because of the renal excretion, zanamivir must be
used cautiously in people with any renal impairment.
It should be used during pregnancy and breastfeeding
only if the benefits clearly outweigh the risks to the fetus
or neonate.
Adverse events, including bronchospasm and/or
decline in respiratory function, some of which have been
serious, have been reported in association with the use
of
Relenza
during the Northern Hemisphere influenza
season. These events have been reported rarely in people
with underlying respiratory disease (asthma, chronic
obstructive pulmonary disease (COPD)) and have also
been reported very rarely in individuals without under-
lying respiratory disease.
Adverse effects
Use of these antiviral agents is frequently associated
with various adverse effects that may be related to
possible effects on dopamine levels in the brain. These
adverse effects include light-headedness, dizziness and
insomnia; nausea; orthostatic hypotension; and urinary
retention.
Clinically important drug–drug interactions
People who receive amantadine may experience increased
atropine-like effects if this drug is given with an anti
cholinergic drug. Ribavirin levels may be reduced if given
with antacids. The use of ribavirin should be avoided
if the person is also receiving a nucleoside reverse tran-
scriptase inhibitor. Rifampicin is known to decrease the
effectiveness of many drugs, including antiarrhythmics,
digoxin, hormonal contraceptives, corticosteroids, anti-
fungals and central nervous system (CNS) depressants.
People should be monitored closely for loss of effective-
ness of these drugs if this combination is used. There is
an increased incidence of rifampicin-related hepatitis if
it is used concurrently with isoniazid. This combination
should be avoided.
Care considerations for people receiving
agents for influenza A and respiratory viruses
Assessment: history and examination
■
■
Assess for
contraindications or cautions
: known
history of allergy to antiviral agents
to avoid
hypersensitivity reactions
; history of liver or
renal dysfunction
that might interfere with drug
metabolism and excretion
; and current status
related to pregnancy or breastfeeding.
■
■
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.
■
■
Assess for orientation and reflexes
to evaluate any
CNS effects of the drug
; vital signs (temperature,
respiratory rate, breath sounds for adventitious
sounds)
to assess for signs and symptoms of
the viral infection;
blood pressure
to monitor
for orthostatic hypotension;
urinary output
to
monitor genitourinary
(
GU
)
effects of the drug;
and renal and hepatic function tests
to determine
baseline function of these organs.
■
■
Assess for adverse events such as bronchospasm
or decline in respiratory function in people using
zanamivir and seek medical advice immediately.
Implementation with rationale
■
■
Start the drug regimen as soon after exposure to
the virus as possible
to enhance effectiveness and
decrease the risk of complications due to viral
infection.
■
■
Administer influenza A vaccine before the flu
season begins, if at all possible,
to decrease the risk
of contracting the flu and also decrease the risk of
complications.
■
■
Administer the full course of the drug
to obtain the
full beneficial effects.
■
■
Provide safety provisions if CNS effects occur
to
protect the person from injury.
■
■
Instruct the person about the appropriate dosage
scheduling regimen; safety precautions, including
changing position slowly and avoiding driving
and hazardous tasks, that should be taken if CNS
effects occur; and the need to report any adverse
effects such as difficulty walking or talking
to
enhance knowledge about drug therapy and to
promote compliance.
