1. Lithium mediates the mechanism of action of lithium salts. Lithium possibly influences the second messenger systems of IP₃, cAMP and DAG by decreasing various enzymes important for re-circulation and conversion of membrane phosphor-inositides. Thus in effect influencing cholinergic and monoamine neurotransmission (Brand, 2021).
2. The therapeutic index of lithium is 0.5-1.5nM, thus it is a very narrow therapeutic index, because with concentrations higher than 2nM toxicity is experienced. The clinical significance of this narrow therapeutic index, is n high risk for toxicity but also doses that is sub-therapeutic. The plasma levels should thus be monitored very carefully (Brand, 2021).
3. In the case of recurrent or resistant depression, lithium can be combined with antidepressants for better antidepressant-effects (SAMA & UCT, 2020).

When a patient does not respond to lithium or valproate as antimanic drugs individually, it can be used in combination with each other (Katzung, 2018).

If a patient does not respond to carbamazepine as mood stabilizer, lithium can be used in combination (Katzung, 2018).

Lithium is otherwise used as a single drug in treating acute manic attacks, treatment for self-mutating or aggressive behaviour and also as prophylaxis for hypomanic and manic episodes (SAMA & UCT, 2020).

4. - Lithium in combination with traditional antipsychotic drugs has an increased or worsened   

  EPS (extrapyramidal symptoms).

- In combination with phenytoin, carbamazepine, losartan, metronidazole, methyldopa and  

  calcium-ion channel blockers it causes neurotoxicity.

- Interaction  caffeine, antacids or theophylline with lithium causes decreased effectiveness    

  due to an increase in the renal excretion of lithium (Brand, 2021).

5. The major side effects of lithium is:

• Weight gain
• Sexual dysfunction
• Fatigue and muscle weakness
• Edema
• Nocturia, polyuria or polydipsia
• Sedation, aphasia, ataxia and tremors
• Acne
• Alopecia
• Nephrogenic diabetes insipidus
• Leucocytosis
• Thyroid enlargement (Brand, 2021).

6. Lithium is a category D in pregnancy (Katzung, 2018). A patient  cannot breastfeed while taking lithium due to the excretion of lithium in high concentration is breast milk (SAMA & UCT, 2020).

7. .

• Treatment of self-mutilating or aggressive behaviour.
• Prophylaxis of hypomanic and manic episodes.
• Treatment of an acute manic episode (SAMA & UCT, 2020).

8./9.) Miss B. Polar is using two drugs along with her lithium-drug causing interaction, both additional drugs is increasing the concentration of lithium in her body. Using the NSAID (Indocid®) caused weight gain, due to the toxicity resulting in combination with lithium (Brand, 2021; Drugs.com, 2020). To try and treat her weight gain she decided to use a diuretic which also causes lithium toxicity. Thus this explains her fatigue, tiredness, polydipsia, feeling shaky and nauseous (Brand, 2021).

My recommendation would be that she stops to use both the diuretic and NSAID. She can rather use another pain stiller such as paracetamol or orphenadrine if she has pain again in the future to help prevent lithium toxicity and thus weight gain (Brand, 2021). She can try to exercise (more) and eat healthy in order to loose the gained weight.

Reference list

Brand, L. 2021. Antipsychotic drugs and lithium salts. Study unit 9 [pdf]. Unpublished lecture notes on eFundi, FKLG312. Potchefstroom, NWU.

Drugs.com. 2020. Indocid (Rectal). https://www.drugs.com/cons/indocid.html Date of access: 1 May 2021.

Katzung, B.G. 2018. Basic & Clinical Pharmacology. 14th ed. International: McGraw-Hill Education.

South African Medical Association (SAMA) & University of Cape Town (UCT). 2020. 13th ed. Pretoria: South African Medical Association