Hypnotics in Clinical Practice
In clinical practice, hypnotic drugs are used to treat sleep-onset disorders. These are specialized medications that induce a specific state of the central nervous system. The primary requirement for such drugs is that the state they induce must closely mimic natural physiological processes.
The main indication for prescribing hypnotics is various forms of sleep disorders, medically termed insomnia. When conducting pharmacotherapy, the clinician pursues two fundamental goals:
- Induction: significantly facilitating the sleep-onset process.
- Maintenance: ensuring adequate and continuous duration of rest.
Physiological Architecture: Phase Alternation
Electroencephalography (EEG) data clearly demonstrate that nocturnal rest is not a uniform process. Based on the pattern of brain wave activity, two regularly alternating phases are distinguished.
1. Non-Rapid Eye Movement Sleep (Non-REM sleep) In scientific literature, this phase is also called slow-wave, orthodox, or synchronized sleep. It dominates the structure of nocturnal rest, accounting for 75 to 80 percent of total time. The development of the orthodox phase occurs sequentially, progressing through four stages:
- Beginning with stage 1, which represents regular drowsiness.
- Gradually deepening up to stage 4, termed delta sleep. At this stage, the EEG records characteristic slow, high-amplitude $\delta$-waves.
2. Rapid Eye Movement Sleep (REM sleep) Its synonyms include rapid, paradoxical, or desynchronized sleep. The paradoxical phase accounts for about 20–25 percent of total rest time. This period is accompanied by vivid dreaming. A characteristic clinical marker of the phase is rapid eye movements (hence the acronym REM). Episodes of desynchronized activity follow a strict cyclicity, repeating every 80–90 minutes.
Neurochemical Control of Sleep and Wakefulness
The alternation of orthodox and paradoxical phases, as well as the maintenance of stable rest, is controlled by a complex set of neurotransmitters and peptides. The balance of these substances determines the quality of central nervous system restoration.
- Serotonin: acts as a key factor that primarily induces (triggers) the sleep-onset process.
- Melatonin: a hormone ensuring phase synchronization and fine regulation of circadian rhythms.
- Inhibitory and opioid systems: gamma-aminobutyric acid (GABA), endorphins, and enkephalins. They provide necessary CNS inhibition.
- Specific factors: for example, delta-sleep-inducing peptide, which regulates the deep stages of the slow-wave phase.
- Wakefulness and modulation mediators: this group includes acetylcholine, dopamine, adrenaline, and histamine. Their activation leads to the termination of rest.
Clinical Typology of Insomnia
Disorders of natural physiological rest are classified based on which stage or parameter of the process is disrupted:
- Presomnic disorders — primary sleep-onset impairment (difficulty with induction).
- Intrasomnic disorders — impairment of depth and quality. Manifested as superficial sleep, frequent groundless nocturnal awakenings, and anxious dreams.
- Postsomnic disorders — impairment of total duration. These include chronic sleep deprivation and early final awakening.
- Structural disorders — pathological alteration of the physiological ratio of slow-wave (80%) and rapid (20%) sleep.