112 HANDBOOK OF PSYCHIATRIC DRUGS

112 HANDBOOK OF PSYCHIATRIC DRUGS

above, particularly if prolonged, can cause central nervous system impairment, renal shutdown, coma, permanent brain injury, and death. Management of severe lithium intoxication (Table 3-11) may require hemodialysis and medical intensive care to maintain fluid and electrolyte balance, prevent further absorption of the drug, and maximize the rate of elimination.

To avoid this, patients and their families need to be instructed carefully on a number of matters related to lithium levels. They should be alerted to the early signs of intoxication—such as increased tremor, confusion, and ataxia—and directed to stop

Management of Serious Lithium Toxicity

1. Rapidly assess (including clinical signs and symptoms, serum lithium levels, electrolytes, and electrocardiogram), monitor vital signs, and make an accurate diagnosis.

2. Discontinue lithium therapy. 3. Support vital functions and monitor cardiac status. 4. Limit absorption.

a. If patient is alert, provide an emetic. b. If patient is obtunded, intubate and suction nasogastrically

(prolonged suction may be helpful because lithium levels in gastric fluid may remain high for days).

5. Prevent infection in comatose patients by body rotation and pulmonary toilet. 6. When lithium has reached nontoxic levels, vigorously hydrate (ideally 5 to 6 L/d); monitor and balance the electrolytes. 7. In moderately severe cases:

a. Implement osmotic diuresis with urea, 20 g given intravenously two to five times per day, or mannitol, 50 to 100 g/d, given intravenously.

b. Increase lithium clearance with aminophylline, 0.5 g up to every 6 hours, and alkalinize the urine with intravenously administered sodium lactate.

c. Ensure adequate intake of sodium chloride to promote excretion of lithium.

8. Implement hemodialysis in the most severe cases. These are characterized by:

a. Serum lithium levels between 2 and 4 mEq/L with severe clinical signs and symptoms (particularly decreasing urinary output and deepening CNS depression).

b. Serum lithium levels greater than 4 mEq/L.

113 taking further lithium and contact their psychiatrist promptly. A

MOOD STABILIZERS

lithium level should be obtained as soon as possible that same day and the symptoms followed closely for the next several days. The psychiatrist should also be contacted if the patient develops new gastrointestinal symptoms, especially vomiting or diarrhea. These symptoms may reflect an elevated lithium level or may, even if caused by an unrelated factor (such as gastrointestinal infection), trigger an elevation in the lithium level as a conse- quence of fluid and electrolyte changes. Other causes of fluid loss with insufficient replacement, such as excessive sweating due to heat exposure or fever, should also prompt a tempo- rary discontinuation of lithium treatment until fluid balance is restored. Concomitant use of other medications may also increase levels of lithium and lead to lithium intoxication (See ‘Drug Interactions’).

The most common adverse effects from lithium are (Table 3-12):

• nausea • vomiting • diarrhea • postural tremor • polydipsia • polyuria

If troublesome, these can usually be mitigated by altering the lithium timing or formulation or by adding a remedy. Specific interventions include the following:

• Beta blocking drugs generally dramatically reduce or completely eliminate lithium tremor. Propranolol is often used and must be dosed b.i.d. or t.i.d. to cover the entire day (unless a long acting form of propranolol is used). Treatment is initiated at 10 mg b.i.d. to t.i.d. and increased as tolerated and needed. Doses above 160 mg are not usually required.

• Diuretics for polydipsia or polyuria. Diuretics may paradox- ically decrease urine volume, but because some (such as thiazides) can also raise the serum lithium concentration, lithium level must be carefully monitored and the lithium dose adjusted downward appropriately. Potassium levels should also be monitored and supplementation may be necessary.