Sedative-Hypnotic and Anxiolytic Drugs: A Comprehensive Overview, Exams of Nursing

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HIP 303 Drugs acting on

Central Nervous System (CNS)

Lesson 2

SEDATIVE-

HYPNOTIC/ANXIOLYTIC DRUGS

Dr. Gitau Chege

Introduction

• Primary use of sedative-hypnotic & anxiolytic drugs is to encourage calmness ( anxiolytics or sedatives ) or to produce sleep (s edative–hypnotics ) - Drug classification is based on clinical uses rather than on similarities in chemical structure.
• All CNS depressants have some ability to relieve anxiety.
  • However, most relieve symptoms of anxiety only at doses that produce noticeable sedation

Introduction

• A sedative drug ↓es activity, moderates excitement, & calms
• A hypnotic drug should produce drowsiness & encourage the onset & maintenance of a state of sleep resembling natural sleep & from which the recipient can be aroused easily
• Hypnotic effects involve more pronounced depression of the CNS than sedation
• Can be achieved with many drugs in this class simply by increasing the dose

Amnesia sedation Hypnosis Coma Death Awake

BASIC PHARMACOLOGY OF SEDATIVE-

HYPNOTICS

 Graded dose-dependent depression of CNS function is a characteristic of most sedative-hypnotics.  However, individual drugs differ in the relationship between the dose & the degree of CNS depression Gitau SC, PhD.

Sleep

• The duration & pattern of sleep varies considerably among individuals
• Age has an important effect on quantity & depth of sleep

Stages of Sleep

• Stage 0 (awake) - 1 - 2 % of sleep time
  • From lying down to falling asleep & occasional nocturnal awakenings.
  • EEG shows α activity when eyes are closed & β activity when eyes are open
  • Eye movements are irregular or slowly rolling.
• Stage 1: (dozing) - 3 – 6 % of sleep time
  • α activity is interspersed with θ waves
  • Eye movements are reduced but there may be bursts of rolling
  • Neck muscles relax.

• Stage 4 (cerebral sleep)- 10 - 20% of sleep time
  • δ activity predominates in EEG
  • K complexes cannot be evoked
  • Eyes are practically fixed; subjects are difficult to arouse
  • Night terror may occur at this time
• NB
• During stage 2, 3 & 4 heart rate, BP & respiration are steady & muscles are relaxed.
• Stages 3 & 4 together are called slow wave sleep (SWS)

Stages of Sleep

• REM sleep (paradoxical sleep)- 20 - 30% of sleep time
  • EEG has waves of all frequency
  • K complexes cannot be elicited
  • Marked, irregular & darting eye movements; dreams & nightmares occur, which may be recalled if the subject is aroused
  • Heart rate & BP fluctuate; respiration is irregular
  • Muscles are fully relaxed, but irregular body movements occur occasionally
  • Erection occurs in males.

CHEMICAL CLASSIFICATION

• Barbiturates
• Ramelteon , a melatonin receptor agonist, is a new hypnotic drug.
• AZAPIRONES e.g., Buspirone is a slow-onset anxiolytic agent whose actions are quite different from those of conventional sedative-hypnotics.
• Other classes of drugs that exert sedative effects include antipsychotics, and many antidepressant drugs.
• Certain antihistaminic agents including hydroxyzine & promethazine are also sedating.

Barbiturates

• Popular hypnotics & sedatives of the last century upto 1960s, but are not used now to promote sleep or to calm patients Condensation of urea & malonic acid to produced barbituric acid

Pharmacokinetics

Absorption

Absorption is rapid & nearly complete Onset of action varies from 10 - 60 minutes ( depend on formulation, & delayed by the presence of food in the stomach. IM injections of sodium salts solutions should be placed deeply into large muscles to avoid the pain & possible necrosis that can result at more superficial sites IV reserved for the management of  status epilepticus (phenobarbital sodium) induction and/or maintenance of general anesthesia (e.g., thiopental or methohexital)