346
P A R T 4
Drugs acting on the central and peripheral nervous systems
levels of lithium occur. Most cases of lithium intoxica-
tion occur as a complication of long-term therapy and
are caused by reduced excretion of the drug because of a
variety of factors including dehydration, deterioration of
renal function, infections, and co-administration of diur
etics or NSAIDs (or other drugs that interact).
Psyllium
People being treated with lithium should be encouraged
not to use the herbal therapy psyllium, which is used to
treat constipation and to lower cholesterol levels. If this
agent is combined with lithium, the absorption of the
lithium may be blocked and the person will not receive
therapeutic levels. If the person feels a need for a drug
to relieve constipation or is concerned about cholesterol
levels, they should be encouraged to discuss alternative
measures with the healthcare provider.
Herbal and alternative therapies
BOX 22.6
Prototype summary: Lithium
Indications:
Treatment of manic episodes of bipolar,
manic-depressive illness.
Actions:
Alters sodium transport in nerve and
muscle cells; inhibits the release of noradrenaline
and dopamine, but not serotonin, from stimulated
neurons; increases the intraneuronal stores of
noradrenaline and dopamine slightly; and decreases
the intraneuronal content of second messengers.
Pharmacokinetics:
Route
Onset
Peak
Duration
Oral
Unknown 0.5–3 hours 8–12 hours
Oral,
extended
release Unknown 4–12 hours 12–18 hours
T
1/2
:
24 hours; excreted in the urine.
Adverse effects:
CNS problems, including lethargy,
slurred speech, muscle weakness and fine tremor;
polyuria, gastric toxicity, with nausea, vomiting
and diarrhoea progressing; CV collapse, coma;
adverse effects are related to serum drug levels.
Care considerations for
people receiving lithium
Assessment: History and examination
■
■
Assess for
contraindications or cautions for the
use of the drug
, including any known allergies to
lithium; renal or CV disease; dehydration; sodium
depletion, use of diuretics, protracted sweating
or diarrhoea; suicidal or impulsive people with
severe depression; pregnancy or breastfeeding; and
infection with fever.
■
■
Assess temperature; skin colour and lesions; CNS
orientation, affect and reflexes; bowel sounds and
reported output; pulse, auscultation and blood
pressure, including orthostatic blood pressure;
respiration rate and adventitious sounds; and
urinary output
for baseline status before beginning
therapy and for any potential adverse effects
.
Also obtain liver and renal function tests, thyroid
function tests, FBC and baseline ECG, and obtain
serum lithium levels as appropriate.
Implementation with rationale
■
■
Administer drug cautiously, with daily monitoring
of serum lithium levels, to people with significant
renal or CV disease, dehydration or debilitation,
as well as those taking diuretics,
to monitor for
toxic levels and to arrange for appropriate dose
adjustment.
■
■
Administer drug with food or milk
to alleviate
GI irritation if GI upset is severe.
■
■
Arrange to decrease dose after acute manic
episodes.
Lithium tolerance is greatest during
acute episodes and decreases when the acute
episode is over.
■
■
Ensure that the person maintains adequate intake
of salt and fluid
to decrease toxicity.
■
■
Monitor person’s clinical status closely, especially
during the initial stages of therapy,
to provide
appropriate supportive management as needed.
■
■
Arrange for small, frequent meals, sugarless
lozenges to suck and frequent mouth care,
to increase secretions and decrease discomfort
as needed.
■
■
Provide safety measures such as side rails and
assistance with ambulation if CNS effects occur
to prevent injury.
■
■
Provide thorough teaching, including drug name,
prescribed dosage, measures for avoidance of
adverse effects, cautions that it may take time
to see the desired therapeutic effects, warning
signs that may indicate possible problems and
the need to avoid pregnancy while taking lithium
to enhance knowledge about drug therapy and to
promote compliance.
■
■
Offer support and encouragement
to help the
person to cope with the drug regimen.
Evaluation
■
■
Monitor response to the drug (decreased
manifestations and frequency of manic
episodes).
