Indications for Use
Mood-stabilizing agents are used to treat conditions associated with severe affective disorders. The primary clinical indications include:
- Bipolar affective disorder (BAD) (also known as manic-depressive psychosis). This condition is characterized by the regular alternation of depressive and manic episodes, separated by periods of full recovery known as intermissions.
- Cyclothymia. This psychiatric disorder features chronic mood instability. Unlike true manic-depressive psychosis, the frequent shifts between emotional lows and highs are less severe and do not reach the same depth.
Drugs in this group effectively manage manic syndrome. Mania is characterized by pathological elation, pathologically increased arousal, excessive physical activity, and a marked acceleration of speech and movement.
Drug Classification
To reliably stabilize emotional background in clinical practice, two main groups of medications are used:
- Lithium salts — the foundational group of mood stabilizers.
- Antiepileptic drugs — in this context, primarily carbamazepine and valproic acid.
Antiepileptic drugs are prescribed to prevent manic-depressive states. They are often used as part of combination therapy, complementing lithium salts when lithium monotherapy proves insufficiently effective.
Pharmacodynamics of Lithium Salts
The exact mechanism of action of lithium is not yet fully established, but pharmacology highlights three key hypotheses:
- Ionic mechanism. Lithium ions can penetrate inside neurons via fast sodium channels. Accumulating intracellularly, they physically block the transmembrane transport of sodium ions, ultimately disrupting normal cell membrane depolarization processes.
- Effects on neurotransmitters. These drugs actively interfere with monoamine metabolism within central nervous system structures.
- Intracellular mechanism. Lithium disrupts the production of crucial secondary messengers that transmit signals inside the cell (including cAMP, diacylglycerol, and inositol-1,4,5-trisphosphate).
Characteristics of Lithium Therapy
The primary representative of this group is lithium carbonate. It is well absorbed from the gastrointestinal tract, but its therapeutic effect sets in quite slowly, requiring a latency period of about 2–3 weeks. The drug possesses selective antimanic action without causing prominent sedative effects. Therapy is prescribed for long-term management (years) for reliable prevention of manic and depressive phases in BAD.
In addition to standard formulations, extended-release preparations and alternative salts exist. Extended-release variants cause less gastrointestinal irritation due to the slow release of the active substance and feature low hygroscopicity.
Safety Profile and Toxicity
Lithium salts have a narrow therapeutic index, making them potentially dangerous to use and requiring rigorous therapeutic drug monitoring.
- Side effects: patients frequently complain of severe thirst, nausea, tremor, polyuria, and muscle weakness.
- Toxic action: occurs when the therapeutic blood concentration is exceeded by only 2–3 times. Acute poisoning manifests as intractable vomiting, seizures, ataxia, and can rapidly progress to coma.
Because lithium preparations are eliminated primarily by the kidneys, any renal pathology is an absolute contraindication to their use. Impairment of excretory function inevitably leads to drug accumulation and a sharp spike in toxicity.