DRUGS ACTING ON CENTRAL NERVOUS SYSTEM
Introduction:
The central nervous system controls thinking, movement, emotions, memory, pain sensation, and consciousness. Drugs acting on the CNS either stimulate or depress brain activity and are used in conditions such as mental illness, seizures, pain, anxiety, sleep disorders, and anesthesia.
Anaesthetics:
Anaesthetics cause loss of sensation by depressing the CNS and are used during medical procedures to prevent pain.
- Local anaesthetics: Act on a specific area
- General anaesthetics: Cause complete unconsciousness
Stages of General Anaesthesia:
- Stage I: Analgesia
- Stage II: Delirium
- Stage III: Surgical anaesthesia
- Stage IV: Medullary paralysis (dangerous stage)
Classification of General Anaesthetics:
- Inhalational agents: Halothane, Enflurane, Ether
- Intravenous agents: Thiopentone sodium, Ketamine, Propofol, Etomidate
- Gaseous anaesthetics: Nitrous oxide
Important Examples:
- Thiopental sodium: Short-acting IV anaesthetic; rapid induction
- Ketamine: NMDA blocker; used in emergency and pediatric procedures
- Propofol: GABA activator; used for sedation and ICU care
Sedatives and Hypnotics:
These drugs depress the CNS. Low doses produce sedation, while higher doses induce sleep.
- Do not relieve pain
- Reduce anxiety and promote sleep
Examples:
- Diazepam: Anxiety, seizures, muscle relaxation
- Alprazolam: Panic and anxiety disorders
- Nitrazepam: Insomnia and seizures
- Phenobarbital: Epilepsy and sedation
Antipsychotics:
Used in schizophrenia, bipolar disorder, and severe behavioural conditions. They mainly act on dopamine and serotonin pathways.
- Chlorpromazine: Schizophrenia, nausea, hyperactivity
- Haloperidol: Psychosis, agitation
- Risperidone: Schizophrenia and bipolar disorder
Anticonvulsants:
Prevent abnormal neuronal activity and are used in epilepsy and seizures.
- Phenytoin: Seizures and neuralgia
- Carbamazepine: Epilepsy and bipolar disorder
- Valproic acid: Seizures, mania, migraine prevention
Antidepressants:
Improve mood by increasing neurotransmitters like serotonin and norepinephrine.
- Amitriptyline: Depression and neuropathic pain
- Fluoxetine: Depression and OCD
- Sertraline: Depression, PTSD, anxiety disorders
