McKenna's Pharmacology for Nursing, 2e

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.

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

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

■ ■ Monitor response to the drug (decreased manifestations and frequency of manic episodes).