Lithium

Sample

1. It is done on the serum of the patient.
2. The time to take the sample is 12 hours after the dose.

Indications

1. It is used particularly in psychiatric patients on lithium therapy :
   1. Mania.
   2. Manic depressive illness (Bipolar affective disorder).
   3. The manic phase of the affective disorder.
   4. For the treatment and prevention of mania and people with bipolar disorders.

Pathophysiology

1. This is present in the ultra-trace amount.
   1. Lithium is an element like sodium and potassium.
   2. Its salt may be found on earth in small quantities.
      1. The amount of river water and the well is very low.
      2. In plants and the animal, the tissue is also low.

2. Metabolism of Lithium

   1. There is the complete absorption of lithium from the GI tract.
   2. The peak level reaches within 2 to 4 hours after the intake of the drug.
   3. This is free in the blood and does not bind to the protein.
   4. The clearance in the blood is biphasic.
   5. First phase: 30 to 40 % cleared with a half-life of 22 hours.
   6. Second phase: The remainder lithium present in the ion pool is cleared with a half-life of 48 to 72 hours.
   7. The clearance is mainly dependant upon the renal function where active absorption occurs.
   8. Decreased renal function causes prolonged clearance time.
      

      Lithium Absorption From the GIT

3. Lithium carbonate is used as a drug to treat patients with bipolar manic depression.
   1.   When given to patients then regulates the neurotransmission in the brain.
4. The lithium level should be monitored very carefully because the Level for the therapeutic dose and toxic dose is very narrow.
   1. Therapeutic level =  0.8 to 1.2 meq/L (meq/L = mmol/L).
   2. Maintinance dose = 0.5 to 1.2 mmol/L.
   3. Toxic level = >2.0 meq/L
      

      Lithium Doses and Optimum Dose

5. There is a lab variation of these values from lab to lab.
6. Decreased dietary sodium leads to a decrease in the excretion of lithium.

Normal

Source 2 

• Therapeutic level: 0.8 to 1.2 meq/L
• Toxic level :  > 2.0 meq/L
• (meq/L = mmol/L, both values are the same)

Source 4

• Acute mania = 0.6 to 1.2 meq/L
• Protection against future episodes in patients with bipolar disorder = 0.8 to 1.0 meq/L
• Toxic level = >2 meq/L

The side effects of the  raised level of lithium:

Clinical presentation	If the lithium level is
Gastrointestinal symptoms	1.5 to 2.0 meq/L
Tremors	1.5 to 2.0 meq/L
Somnolence	2.0 to 2.5 meq/L
Seizures	>2.5 meq/L
Death	>2.5 meq/L

Stop the medicine when the patient feels the following signs and symptoms:

1. The patient has dizziness, or drowsiness, or a lake of energy.
2. There may be muscle weakness.
3. The patient may have nausea, vomiting, or diarrhea.
4. Difficulty in speech.
5. There may be a lack of coordination.
6. The patient may be confused.
7. May get irregular tremors or shaking.
8. There may be restlessness.

• The recommended time for the lithium estimation is 12 hours after the dose:

Mechanism of Lithium action

1. This enhances the reuptake of catecholamines.
2. So it decreases their concentration in the neuronal junction.
3. This reduced level produces a sedation effect on CNS.
4. Lithium also modulates the distribution of sodium, calcium, magnesium in the nerve cells.
5. Also, regulate the glucose metabolism that affects the nerve function.
6. The clearance is done by the kidneys. So in the case of renal damage, the clearance is delayed.
   

   Lithium Effect on Nerves

Treatment

• Lithium is given to the patient as lithium carbonate.

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