CNS Depressants Class PDF

CNS Sedative-Hypnotic Drugs Chapter 37 (see also anxiolytic drugs) CNS Depressants Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: Nervousness Excitability Irritability Without causing sleep CNS Depressants Hypnotic...

CNS Sedative-Hypnotic Drugs Chapter 37 (see also anxiolytic drugs) CNS Depressants Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: Nervousness Excitability Irritability Without causing sleep CNS Depressants Hypnotics Reduce CNS function to the point that they cause sleep A sedative can become a hypnotic if given in large enough doses CNS Depressants Sedative-hypnotics: At low doses, depress CNS function without inducing sleep At higher doses, depress CNS function to the point of causing sleep  Barbiturates vs Benzodiazapines CNS Depressants Take home message Benzodiazapienes are much more commonly used as sedative-hypnotics (and anxiolytics) better pharmacological profile better adverse effects profile Be aware of barbiturate uses Sedative-Hypnotics: Barbiturates: Indications Sedative – Hypnotic now rarely used for this but low doses might be used Antiepileptic can raise the seizure threshold thus reducing seizures Anaesthesia for surgical procedures for short procedures Barbiturates Short acting PenTObarbital (rarely used) Long acting Phenobarbital eg antiepileptic Therapeutic Index Barbiturates have a narrow therapeutic index – need to be monitored Barbiturates: Mechanism of Action Site of action Most have broad CNS depression action Potentiates GABA action and mimics GABA Metabolized in liver and excreted in urine Barbiturates: Toxicity and Overdose Overdose frequently leads to respiratory depression, and subsequently, respiratory arrest Overdose produces CNS depression (sleep to coma and death) Can be therapeutic Anaesthesia induction Uncontrollable seizures: “phenobarbital coma” Barbiturates Reduced clinical use of barbiturates due to: Tolerance Physical dependence Liver enzyme induction Abuse potential Powerful respiratory depressants (no tolerance development) No antidote Benzodiazepines CNS Depressants: Benzodiazepines Most frequently prescribed sedative- hypnotics one of the most commonly prescribed drug classes favourable adverse effect profiles compared to barbiturates good efficacy and safety profile CNS Depressants: Benzodiazepines Classified as either: Sedative-hypnotic Anxiolytic (medication that relieves anxiety) Benzodiazepines: Sedative-Hypnotic Long acting chlordiazepoxide, clorazepate, flurazepam Intermediate acting lorazepam (Ativan), oxazepam Short acting Midazolam (Versed) (IV), triazolam Conscious sedation - amnesic property Benzodiazepines: Mechanism of Action Benzodiazepines: Mechanism of Action GABA reduces excitability of neurones Fewer action potentials in nerve cells Benzodiazepines enhances effect of GABA Decreased neuronal excitability =Depress CNS activity  Benzodiazepines Affect hypothalamic, thalamic, and limbic systems of the brain Do not suppress REM sleep as much as barbiturates Do not increase metabolism of other drugs PO administration does NOT depress respiration excessively but can in overdose when combined with other CNS depressants and when given IV Flumazenil used to reverse BZD overdose BZD receptor antagonist Much better than Barbiturates Benzodiazepines: Drug Effects Useful in controlling agitation and anxiety Reduce excessive sensory stimulation, inducing sleep especially in short term use for insomnia due to anxiety Induce skeletal muscle relaxation Benzodiazepines: Indications Sedation Sleep induction Skeletal muscle relaxation (central effect) Anxiety relief Treatment of alcohol withdrawal Agitation Epilepsy Balanced anaesthesia Benzodiazepines: Adverse Effects Drowsiness Headache Dizziness Vertigo Lethargy Paradoxical excitement (nervousness) “Hangover effect” Benzodiazepines: Interactions All other CNS depressants alcohol, opioids - have cumulative effects Grapefruit alters drug absorption Cimetidine inhibits benzodiazepine metabolism Herbs kava, valerian and chamomile increase CNS depression Client Care Implications Clients should be instructed to avoid Alcohol other CNS depressants Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued dosage reduced gradually Other Hypnotics BZD – like drugs Structurally different from BZD Same drug target as BZD Zolpidem (Ambien), zaleplon, zopiclone Short-term use in management of insomnia