CNS drugs

• Central Nervous System (CNS)

  These drugs target the neurotransmitters of the CNS & results in a range of effects
• Psychotropic drugs


  Capable of changing emotional behaviour
• Psychotropic drugs

  • Anxiolytics and Sedative Hypnotics
  • Neuroleptics/Antipsychotics
  • Antidepressants
  • Psychostimulants
  • Psychotomimetics
• Other CNS drugs


  • Anti-Epileptic drugs
  • Anti-Parkinsons Drugs
  • Anti-Emetics
• Anxiety


  Usually occurs in response to a threat that is unknown, internal, vague and conflicting
• Anxiety disorders


  • Panic disorder
  • Phobias
  • OCD
  • Post traumatic stress disorder
  • Generalised anxiety disorder
• Anxiolytics


  Medication which reduces anxiety and has a calming effect on patient behaviour
• Sedative Hypnotics

  Drugs that cause drowsiness and encourage the onset of sleep
• In low doses, sedative hypnotics can be used as anxiolytics
• Benzodiazepines


  Naming pattern: ends with "pam" or "lam" e.g. diazepam, lorazepam, flunitrazepam, clonazepam, alprazolam, midazolam, loprazolam
• Other indications for benzodiazepines

  • Pre-anaesthesia
  • Induction anaesthesia
  • Aids to endoscopies
  • Delirium tremens
• Therapeutic effects of benzodiazepines

  • Anxiolytics
  • Sedative-hypnotics
  • Anticonvulsant properties
  • Muscle relaxant properties
• Examples of benzodiazepines


  • Sedative hypnotics
  • Anxiolytics
  • Antagonists
• Short and ultra short acting benzodiazepines

  • Midazolam (Dormicum)
  • Triazolam (Halcion)
• Mechanism of action of benzodiazepines

  Enhancement of GABA (Gamma–aminobutyric acid), an inhibitory CNS transmitter. Reduces anxiety, induces relaxation and sleep, depression of convulsions, relaxation of skeletal muscles
• Adverse effects of benzodiazepines

  • Drowsiness
  • Over-sedation
  • Disorientation
  • Confusion
  • Inertia, slurred speech and ataxia
  • Floppy baby syndrome
  • Residual sedation or 'hangover'
  • Cognitive disturbances
  • Paradoxical effects
  • Dependency
• Non-benzodiazepine hypnotics


  Less dependence producing than the benzodiazepines. Do not have anticonvulsant or anxiolytic actions. Used in the management of insomnia
• Non-benzodiazepine hypnotics


  • Zolpidem (Stilnox)
  • Zopiclone (Imovane)
• Psychoses


  More severe types of psychiatric disorders. Impairment in behaviour, Inability to think coherently. Schizophrenia and related disorders
• Antipsychotics/Neuroleptics


  Drug treatment for psychoses
• Mechanism of action of typical antipsychotics

  Block post-synaptic dopamine (D2) receptors
• Mechanism of action of atypical antipsychotics

  Target other neurotransmitters e.g. serotonin. Have less extrapyramidal side effects
• Examples of typical and atypical antipsychotic drugs

  • Typical antipsychotics: Phenothiazines (Chlorpromazine, Trifluoperazine, Prochlorperazine), Benzamides (Sulpiride), Butyrophenones (Haloperidol)
  • Atypical antipsychotics: Clozapine, Olanzapine, Risperidone, Quetiapine
• Pharmacological effects of antipsychotics

  • Block: dopamine, cholinergic, alpha, serotonin, histamine receptors
  • Variety of adverse effects but also varied indications e.g. anti-emetic
• Receptor blockade effects of antipsychotics

  • D2 (mesolimbic & mesocortical pathways): Antipsychotic effects
  • D2 (nigrostriatal pathway): Extrapyramidal effects (EPS)
  • D2 (tuberoinfundibular pathway): ↑ prolactin release (hyperprolactinaemia)
  • D2 (chemo-emetic trigger zone): Anti-emetic effect
  • Muscarinic: Anticholinergic effects
  • Alpha-adrenergic: Postural hypotension
  • Serotonin: Antipsychotic effects with ↓EPS
  • Histamine-1: Weight gain, sedation
• Adverse effects of antipsychotics

  • Extrapyramidal side effects (EPS): Parkinsonism, Dystonic reactions, Akathisia, Tardive dyskinesia
  • Neuroleptic Malignant Syndrome (NMS): Muscle rigidity and hyperthermia
• Therapeutic uses of antipsychotics

  • Schizophrenia
  • Psychosis
  • Uncontrollable attack of hiccoughs
  • Anaesthesia (pre-anaesthesia)
  • Nausea and vomiting
  • Tourette's syndrome
• Depression


  Caused by shortage of noradrenaline and /serotonin in the CNS
• Aim of depression treatment

  To increase the level of noradrenaline and /serotonin
• Depressive disorders


  • Major depression
  • Major depressive disorder with dysthymia
  • Bipolar disorders
• Extrapyramidal side effects (EPS)

  • Parkinsonism - Muscle rigidity, tremor
  • Dystonic reactions - Uncoordinated spasm
  • Akathisia - Inward restlessness and inability to sit still
  • Tardive Dyskinesia - Chewing movements and smacking lips
• Neuroleptic Malignant Syndrome (NMS)

  • Rare but fatal
  • Muscle rigidity and hyperthermia
• Therapeutic Uses of Antipsychotics/Neuroleptics

  • Schizophrenia - Chlorpromazine
  • Psychosis - Haloperidol
  • Anaesthesia (pre-anaesthesia) - Droperidol
  • Nausea and vomitting - Prochlorperazine (Stemetil)
  • Tourette's syndrome - Haloperidol, risperidone
• Depression


  Caused by shortage of noradrenaline and/or serotonin in the CNS
• Treatment Aim for Depression

  To increase the level of noradrenaline and/or serotonin
• Depressive Disorders


  • Major depression
  • Major depressive disorder with dysthymia
  • Bipolar disorders
• Major Depressive disorder with dysthymia

  • Emotional withdrawal
  • Low self-esteem
  • Lack of motor movements
  • Accompanied by anxiety symptoms
• Bipolar Disorders


  Occurrence of one or more manic episodes, accompanied by a major depressive disorder
• Types of Antidepressants


  • Tricyclic Antidepressants (TCAs)
  • Selective Serotonin Reuptake Inhibitors (SSRIs)
  • Monoamine Oxidase Inhibitors (MAOIs)
  • Tetracyclic antidepressants
  • Others e.g. SNRIs, Lithium carbonate
• Tricyclic Antidepressants (TCAs)


  Inhibit re-uptake of noradrenaline (NA) & serotonin (5-HT)