Drugs - Lithium 02

Question 1

Why should plasma levels of lithium be closely monitored?

Answer 1

It has a narrow therapeutic index of as low as 2 or 3

Question 2

What do you need to keep the dose of lithium under?

Answer 2

1.5 mEq/L

Question 3

What are the side effects of lithium when the levels are kept below 1.5?

Answer 3

• GI distress: anorexia, nausea, vomiting, diarrhea
• polyurea and polydipsia
• fine hand tremor (treat with beta blocker propranolol)
• slight muscle weakness

Question 4

What are the side effects of lithium when levels are between 1.5 and 2.5?

Answer 4

• Persistent or recurrent G.I. effects
• coarse hand tremor
• muscle hyperirritability
• slurred speech
• confusion or somnolence
• profuse diarrhea

Question 5

What are the side effects of lithium levels are above 2.5?

Answer 5

Serious lithium toxicity:

• increased deep tendon reflexes
• irregular pulse
• hypotension
• epileptic seizures
• stupor or coma

Question 6

What are the overall side effects of lithium therapy?

Answer 6

• Renal: produces mild nephrogenic diabetes insipidus that manifests as polyurea because it interferes with the activation of adenylyl cyclase by ADH (vasopressin), also decreased water reabsorption and unresponsive to ADH administration
• aggravation of psoriasis and acne (hair loss, dermatitis)
• weight gain
• non-toxic goiter and hypothyroidism (dry skin, coarse skin, tired, cold intolerance)
• Leukocytosis (high white blood cells)

Question 7

What does lithium compete with for reabsorption in the renal tubules?

Answer 7

Sodium

Question 8

Anything that causes an increased loss of sodium in the body is going to do what for lithium absorption?

Answer 8

Increase lithium absorption and toxicity

Question 9

What is the effect of thiazide diuretics on lithium excretion?

Answer 9

They can reduce lithium excretion by as much as 50% so reduce the dose of lithium by as much as 50% and monitor serum levels closely

Question 10

Is there a problem with using loop diuretics with lithium?

Answer 10

No

Question 11

What does increased sodium in the diet do to lithium?

Answer 11

It increases the excretion of lithium while low-sodium or diuretics retain lithium

Question 12

Why is there a paradoxical effect of thiazide diuretics producing less urine volume in lithium treated patients compared to that of patients taking lithium alone?

Answer 12

Because 80% of lithium is usually reabsorbed normally, but when sodium is depleted 86% is reabsorbed, less reaches the distal tubule, and lithium has a smaller effect on the inhibition of ADH and more water is reabsorbed

Question 13

What happens with the coadministration of NSAIDS and lithium?

Answer 13

Coadministration of NSAIDS can increase lithium toxicity by inhibiting its excretion