Mental health disorders such as anxiety, depression, and stress-related conditions, alongside the medical need for anesthesia and sedation, have made psychotropic drugs some of the most widely prescribed medications globally. These drugs act on the central nervous system (CNS), targeting neurotransmitters like GABA, serotonin, and norepinephrine to restore chemical balance and provide therapeutic relief.
Anesthetics and Antianxiety Drugs
1. Local Anesthetics
Suffix: -caine
Examples: Lidocaine, Bupivacaine, Procaine
Mechanism: Block sodium channels in neuronal membranes → prevent nerve impulse conduction → local loss of sensation.
Uses: Minor surgical procedures, dental procedures, regional anesthesia.
Side Effects: CNS toxicity (tremors, seizures), cardiovascular toxicity (arrhythmias, hypotension).
2. Barbiturates (CNS Depressants)
Suffix: -barbital
Examples: Phenobarbital, Pentobarbital
Mechanism: Enhance GABA-A receptor activity → prolonged chloride channel opening → sedation and CNS depression.
Uses: Sedation, anesthesia induction, seizure control.
Side Effects: Respiratory depression, dependence, drug interactions.
3. Benzodiazepines (for Anxiety and Sedation)
Suffixes:
- -zolam → Alprazolam, Midazolam
- -zepam → Diazepam, Lorazepam, Clonazepam
Mechanism: Potentiate GABA-A receptor activity → increase frequency of chloride channel opening → anxiolysis, sedation, muscle relaxation.
Uses: Anxiety disorders, insomnia, seizures, pre-anesthesia medication, alcohol withdrawal.
Side Effects: Sedation, tolerance, dependence, withdrawal symptoms (if abruptly discontinued).
Antidepressants
Depression is a leading cause of disability worldwide, affecting over 280 million people (WHO data). Antidepressants aim to restore balance of neurotransmitters, primarily serotonin, norepinephrine, and dopamine.
1. Selective Serotonin Reuptake Inhibitors (SSRIs)
Suffixes: -oxetine, -talopram, -zodone
Examples: Fluoxetine, Citalopram, Escitalopram, Trazodone
Mechanism: Inhibit serotonin (5-HT) reuptake → increased serotonin in synaptic cleft → improved mood.
Uses: Depression, anxiety, OCD, PTSD, bulimia.
Side Effects: Nausea, sexual dysfunction, insomnia, serotonin syndrome (with other serotonergic drugs).
2. Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs/DNRIs)
Suffixes: -faxine, -zodone, -nacipram
Examples: Venlafaxine, Desvenlafaxine, Levomilnacipran
Mechanism: Inhibit reuptake of both serotonin and norepinephrine.
Uses: Major depressive disorder, generalized anxiety disorder, neuropathic pain, fibromyalgia.
Side Effects: Hypertension, sweating, insomnia, withdrawal symptoms.
3. Tricyclic Antidepressants (TCAs)
Suffixes: -triptyline, -pramine
Examples: Amitriptyline, Nortriptyline, Imipramine, Clomipramine
Mechanism: Block reuptake of serotonin and norepinephrine; also antagonize histamine and muscarinic receptors.
Uses: Depression, neuropathic pain, migraine prophylaxis, enuresis (bedwetting).
Side Effects: Anticholinergic effects (dry mouth, constipation, blurred vision), arrhythmias, weight gain, sedation.
Mechanisms of Action – Simplified Overview
| Drug Class | Neurotransmitter/System Targeted | Effect |
|---|---|---|
| Local Anesthetics (-caine) | Sodium channels | Block nerve impulse → anesthesia |
| Barbiturates (-barbital) | GABA-A | CNS depression, sedation |
| Benzodiazepines (-zolam, -zepam) | GABA-A | Anxiolysis, sedation |
| SSRIs (-oxetine, -talopram, -zodone) | Serotonin reuptake | ↑ Serotonin → improved mood |
| SNRIs (-faxine, -nacipram) | Serotonin & norepinephrine reuptake | ↑ Mood, ↓ pain perception |
| TCAs (-triptyline, -pramine) | Serotonin & norepinephrine reuptake + receptor blockade | Antidepressant, analgesic |
Clinical Applications
1. Anxiety Disorders:
- First-line: SSRIs and SNRIs.
- Acute relief: Benzodiazepines (short-term only due to dependence risk).
2. Major Depressive Disorder (MDD):
- First-line: SSRIs and SNRIs.
- Resistant cases: TCAs, MAO inhibitors, or atypical antidepressants.
3. Insomnia:
- Short-acting benzodiazepines (e.g., temazepam) or non-benzodiazepine hypnotics.
4. Chronic Pain & Fibromyalgia:
- SNRIs (duloxetine) and TCAs (amitriptyline) are effective.
5. Surgical Anesthesia & Sedation:
- Local anesthetics (-caine) for minor procedures.
- Midazolam (a benzodiazepine) for preoperative sedation.
Quick Reference Table
| Drug Class | Common Suffix | Examples | Clinical Use |
|---|---|---|---|
| Local anesthetics | -caine | Lidocaine, Bupivacaine | Local anesthesia |
| Barbiturates | -barbital | Phenobarbital | Seizures, sedation |
| Benzodiazepines | -zolam, -zepam | Alprazolam, Diazepam | Anxiety, seizures, insomnia |
| SSRIs | -oxetine, -talopram, -zodone | Fluoxetine, Citalopram | Depression, anxiety |
| SNRIs | -faxine, -nacipram | Venlafaxine, Levomilnacipran | Depression, neuropathic pain |
| TCAs | -triptyline, -pramine | Amitriptyline, Imipramine | Depression, migraine prophylaxis |
Frequently Asked Questions (FAQs)
Q1. What is the difference between benzodiazepines and barbiturates?
Both act on GABA receptors, but benzodiazepines are safer, have less risk of respiratory depression, and are preferred for anxiety and sedation.
Q2. Why are SSRIs considered first-line antidepressants?
They have a favorable safety profile, fewer side effects, and lower risk of overdose compared to TCAs and MAO inhibitors.
Q3. Can antidepressants cause dependence?
Unlike benzodiazepines, SSRIs and SNRIs are not addictive, but sudden discontinuation may cause withdrawal symptoms.
Q4. Why are TCAs less commonly prescribed now?
Due to their significant side effects and risk of cardiotoxicity in overdose, they are reserved for resistant cases.
Q5. What is serotonin syndrome?
A potentially life-threatening condition caused by excessive serotonergic activity, leading to agitation, sweating, tremors, hyperthermia, and seizures.
Q6. Are local anesthetics safe during pregnancy?
Some (like lidocaine) are considered relatively safe, but always require physician supervision.
