Analgesics, Tranquilizers, Antidepressants — Revision Notes

⚡ 30-Second Revision

Analgesics: — Pain relievers.

- Non-Opioids: - NSAIDs (e.g., Aspirin, Ibuprofen): Inhibit COX enzymes. $E_{pain} downarrow$ - Paracetamol: Analgesic, antipyretic; weak anti-inflammatory. Hepatotoxic in overdose. - Opioids: (e.g., Morphine, Codeine): Act on opioid receptors. Potent, high addiction potential. Respiratory depression.

Tranquilizers (Anxiolytics): — Reduce anxiety.

- Benzodiazepines: (e.g., Diazepam): Enhance GABA-A receptor activity (increase Cl- frequency). Sedative, anxiolytic. - Barbiturates: (e.g., Phenobarbital): Enhance GABA-A receptor activity (increase Cl- duration). Higher toxicity.

Antidepressants: — Treat depression.

- SSRIs: (e.g., Fluoxetine): Selective Serotonin Reuptake Inhibitors. Increase synaptic 5-HT. - TCAs: (e.g., Imipramine): Tricyclic Antidepressants. Block NE & 5-HT reuptake. Anticholinergic side effects. - MAOIs: (e.g., Phenelzine): Monoamine Oxidase Inhibitors. Prevent monoamine breakdown. 'Cheese reaction' risk.

2-Minute Revision

Neurologically active drugs modulate CNS function. Analgesics relieve pain. Non-opioids like NSAIDs (Aspirin, Ibuprofen) inhibit COX enzymes, reducing prostaglandins, effective for mild-moderate pain and inflammation.

Paracetamol is analgesic/antipyretic but weakly anti-inflammatory, with hepatotoxicity risk in overdose. Opioids (Morphine, Codeine) act on opioid receptors for severe pain, causing euphoria, respiratory depression, and high addiction potential.

Tranquilizers (anxiolytics) reduce anxiety. Benzodiazepines (Diazepam) enhance GABA's inhibitory effect at GABA-A receptors, increasing chloride influx, leading to sedation and anxiolysis. Antidepressants treat mood disorders.

SSRIs (Fluoxetine) selectively block serotonin reuptake, increasing synaptic serotonin. TCAs (Imipramine) block both serotonin and norepinephrine reuptake but have significant anticholinergic side effects.

MAOIs (Phenelzine) inhibit monoamine oxidase, preventing neurotransmitter breakdown, but carry a risk of hypertensive crisis with tyramine-rich foods. Key is to link drug class, specific examples, and their primary mechanism of action.

5-Minute Revision

Neurologically active drugs are crucial in medicinal chemistry, targeting the CNS to manage pain, anxiety, and depression. Analgesics are pain relievers. They are broadly categorized into non-opioids and opioids.

Non-opioids include NSAIDs like Aspirin and Ibuprofen, which inhibit cyclooxygenase (COX) enzymes, thereby reducing the synthesis of prostaglandins responsible for pain and inflammation. They are effective for mild to moderate pain.

Paracetamol (Acetaminophen) is another non-opioid, primarily analgesic and antipyretic, but with weak anti-inflammatory action; its overdose is severely hepatotoxic. Opioid analgesics, such as Morphine and Codeine, are potent drugs for severe pain.

They act by binding to specific opioid receptors in the CNS, leading to pain relief, euphoria, and significant side effects like respiratory depression and a high potential for physical dependence and addiction.

Codeine is a prodrug, converted to morphine.

Tranquilizers, also known as anxiolytics, are used to reduce anxiety. Benzodiazepines like Diazepam are a prominent class. Their mechanism involves enhancing the inhibitory effects of the neurotransmitter GABA at the GABA-A receptor.

They increase the frequency of chloride channel opening, hyperpolarizing neurons and reducing overall brain excitability, resulting in a calming effect. Barbiturates, an older class (e.g., Phenobarbital), also enhance GABA but increase the *duration* of chloride channel opening, making them more potent and dangerous in overdose.

Antidepressants are used to treat depression and other mood disorders, often by modulating monoamine neurotransmitter levels. Selective Serotonin Reuptake Inhibitors (SSRIs), such as Fluoxetine, are widely used.

They selectively block the reuptake of serotonin into the presynaptic neuron, increasing its concentration in the synaptic cleft. Tricyclic Antidepressants (TCAs) like Imipramine block the reuptake of both serotonin and norepinephrine but also block other receptors, leading to significant anticholinergic side effects (dry mouth, blurred vision).

Monoamine Oxidase Inhibitors (MAOIs), like Phenelzine, inhibit the enzyme monoamine oxidase, which metabolizes monoamines, thus increasing their levels. MAOIs require strict dietary restrictions to avoid a hypertensive crisis ('cheese reaction').

Understanding these distinct mechanisms and examples is vital for NEET.

Prelims Revision Notes

Analgesics, Tranquilizers, Antidepressants: NEET Quick Notes

I. Analgesics (Pain Relievers)

Definition: — Relieve pain without loss of consciousness.
Classes:

* Non-Opioid Analgesics: * NSAIDs (Non-Steroidal Anti-Inflammatory Drugs): * Examples: Aspirin, Ibuprofen, Naproxen, Diclofenac, Celecoxib. * Mechanism: Inhibit Cyclooxygenase (COX) enzymes (COX-1 & COX-2), reducing prostaglandin synthesis.

* Uses: Mild-to-moderate pain, inflammation, fever. * Side Effects: Gastric irritation/ulcers, renal impairment, cardiovascular risks. * Paracetamol (Acetaminophen): * Mechanism: Believed to involve central COX inhibition; weak peripheral anti-inflammatory.

* Uses: Analgesic, antipyretic (fever reducer). * Side Effects: Hepatotoxicity in overdose (due to NAPQI metabolite). * Opioid Analgesics (Narcotic Analgesics): * Examples: Morphine, Codeine, Heroin, Fentanyl, Pethidine.

* Mechanism: Bind to opioid receptors ($mu, kappa, delta$) in CNS, inhibiting pain transmission. * Uses: Moderate-to-severe pain. * Side Effects: Respiratory depression (most dangerous), sedation, constipation, nausea, vomiting, miosis, euphoria.

* Key Point: High potential for physical dependence and psychological addiction. Codeine is a prodrug (metabolized to morphine).

II. Tranquilizers (Anxiolytics / Sedatives-Hypnotics)

Definition: — Reduce anxiety, promote calmness/sedation.
Classes:

* Benzodiazepines: * Examples: Diazepam, Chlordiazepoxide, Lorazepam, Alprazolam. * Mechanism: Enhance the effect of GABA (gamma-aminobutyric acid) at GABA-A receptors. Increase *frequency* of Cl- channel opening, leading to neuronal hyperpolarization.

* Uses: Anxiety disorders, insomnia, muscle spasms, seizures. * Side Effects: Sedation, drowsiness, impaired coordination. Potential for dependence. * Barbiturates: * Examples: Phenobarbital, Thiopental.

* Mechanism: Enhance GABA-A receptor activity. Increase *duration* of Cl- channel opening. Can directly open Cl- channels at high doses. * Uses: Anticonvulsant, anesthetic induction (historically for anxiety/insomnia).

* Side Effects: Profound CNS depression, respiratory depression, high overdose risk, high dependence potential.

III. Antidepressants (Mood Modulators)

Definition: — Alleviate symptoms of depression and other mood disorders.
Monoamine Hypothesis: — Depression linked to deficiency of monoamine neurotransmitters (serotonin, norepinephrine, dopamine).
Classes:

* SSRIs (Selective Serotonin Reuptake Inhibitors): * Examples: Fluoxetine (Prozac), Sertraline, Paroxetine, Escitalopram. * Mechanism: Selectively block reuptake of serotonin (5-HT) into presynaptic neuron, increasing synaptic 5-HT.

* Uses: Major depressive disorder, anxiety disorders, OCD. * Side Effects: Nausea, sexual dysfunction, insomnia. Generally well-tolerated. * TCAs (Tricyclic Antidepressants): * Examples: Imipramine, Amitriptyline, Nortriptyline.

* Mechanism: Block reuptake of both norepinephrine (NE) and serotonin (5-HT). Also block muscarinic, histamine, and alpha-adrenergic receptors. * Uses: Depression, neuropathic pain. * Side Effects: Anticholinergic effects (dry mouth, blurred vision, constipation, urinary retention), sedation, orthostatic hypotension, cardiotoxicity (in overdose).

* MAOIs (Monoamine Oxidase Inhibitors): * Examples: Phenelzine, Tranylcypromine. * Mechanism: Inhibit Monoamine Oxidase (MAO) enzyme, preventing breakdown of NE, 5-HT, and dopamine, thus increasing their levels.

* Uses: Atypical depression, treatment-resistant depression. * Side Effects: Orthostatic hypotension. Critical: 'Cheese reaction' (hypertensive crisis) with tyramine-rich foods. Serotonin syndrome with other serotonergic drugs.

Vyyuha Quick Recall

To remember the main classes and their actions: All Three Are Neuro-active.

Analgesics: Pain Out (P for Paracetamol/NSAIDs, O for Opioids)
Tranquilizers: GABA Boost (GABA for mechanism, B for Benzodiazepines/Barbiturates)
Antidepressants: Serotonin Norepinephrine Modulators (S for SSRIs, N for TCAs, M for MAOIs)