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P A R T 4
Drugs acting on the central and peripheral nervous systems
■■
Dopaminergic drugs are used to increase the effects
of dopamine at receptor sites, restoring the balance of
neurotransmitters in the basal ganglia.
■■
The adverse effects associated with these drugs are
related to the systemic effects of dopamine, increased
KEY POINTS
heart rate, increased blood pressure, decreased GI
activity and urinary retention.
■■
Levodopa is the standard dopaminergic used to treat
parkinsonism and Parkinson’s disease. Several other
dopaminergics are now used as adjuncts to levodopa
to increase the dopamine effects as long as possible.
CRITICAL THINKING SCENARIO
Effects of vitamin B
6
intake on levodopa levels
THE SITUATION
S.S., a 58-year-old man with well-controlled Parkinson’s
disease, presents with severe nausea, anorexia, fainting
spells and heart palpitation. He has been maintained on
levodopa for the Parkinson’s disease and he claims to have
followed his drug regimen religiously.
According to S.S. the only change in his lifestyle has
been the addition of several health foods and vitamins.
His daughter, who recently returned from her first year
at university, has begun a new health regimen, including
natural foods and plenty of supplemental vitamins. She was
so enthusiastic about her new approach that everyone in
the family agreed to give this diet a try.
CRITICAL THINKING
Based on S.S.’s signs and symptoms, what has probably
occurred?
In Parkinson’s disease, is it possible to differentiate a
deterioration of illness from a toxic reaction to a drug?
What care implications should be considered when
teaching S.S. and his family about the effects of
vitamin B
6
on levodopa levels?
In what ways can the daughter cope with her role in this
crisis?
Develop a new care plan for S.S. that involves all family
members and that includes drug teaching.
DISCUSSION
The presenting symptoms reflect an increase in Parkinson’s
symptoms, as well as an increase in peripheral dopamine
reactions (e.g. palpitations, fainting, anorexia, nausea). It is
necessary to determine whether the problem involves a
further degeneration in the neurons in the substantia nigra
or the particular medication that S.S. has been taking. In
many people, responsiveness to levodopa is lost as neural
degeneration continues.
The explanation of the new lifestyle—full of grains,
natural foods and vitamins—alerts the nurse to the
possibility of excessive vitamin B
6
intake. In reviewing the
vitamin bottles and some of the food packages supplied by
S.S., it seems that too much vitamin B
6
, which speeds the
conversion of levodopa to dopamine before it can cross
the blood–brain barrier, might be the reason the person’s
symptoms recurred.
The status of S.S.’s Parkinson’s disease should be
evaluated, and then he can be restarted on levodopa. The
smallest dose possible should be used initially, with gradual
increases to achieve the maximum benefit with the fewest
side effects. It would be wise to consider combining the drug
with carbidopa to prevent some of S.S.’s recent problems.
In addition, S.S. should receive thorough drug teaching
in written form for future reference. The need to avoid
vitamin B
6
should be emphasised. The entire family should
be involved in an explanation of what happened and how
this situation can be avoided in the future. Because the
daughter may feel guilty about her role, she should have
the opportunity to discuss her feelings and explore the
positive impact of healthy food on nutrition and quality of
life. This situation can serve as a good teaching example
for staff, as well as present them with an opportunity to
review drug therapy in Parkinson’s disease and the risks and
benefits of more extreme diets.
CARE GUIDE FOR S.S.: LEVODOPA
Assessment: History and examination
Allergies to levodopa; chronic obstructive pulmonary
disease (COPD); dysrhythmias, hypotension, hepatic or
renal dysfunction; psychoses; peptic ulcer; glaucoma
Concurrent use of MAO inhibitors, phenytoin, pyridoxine,
papaverine or tricyclic antidepressants (TCAs)
Focus physical examination on:
CV: blood pressure, pulse rate, peripheral perfusion,
electrocardiogram results
CNS: orientation, affect, reflexes, grip strength
Renal: output, bladder palpation
GI: abdominal examination, bowel sounds
Respiratory: respiration, adventitious sounds
Laboratory tests: renal and liver function tests, full blood
count
Implementation
Ensure safe and appropriate administration of drug.
Provide comfort and safety: slow positioning changes;
assess orientation, provide pain medication as needed;
