Drugs in Psychiatric Disorders Practice Questions

Q: Dry mouth during antidepressant therapy is caused by blockade of which receptors?

Muscarinic acetylcholine receptors. **Explanation:** Dry mouth (xerostomia) is a classic side effect of several antidepressant classes, most notably **Tricyclic Antidepressants (TCAs)** like Amitriptyline and certain SSRIs/SNRIs. **1. Why Muscarinic Acetylcholine Receptors are correct:** The salivary glands are primarily under the control of the parasympathetic nervous system. Stimulation of **M3 muscarinic receptors** by acetylcholine normally triggers watery salivation. Many antidepressants possess potent **anticholinergic (antimuscarinic)** properties. By blocking these receptors, the drugs inhibit parasympathetic signaling, leading to decreased secretions, resulting in dry mouth, blurred vision, urinary retention, and constipation. **2. Analysis of Incorrect Options:** * **Serotonergic receptors:** Blockade or stimulation of these receptors (e.g., 5-HT2) is associated with side effects like sexual dysfunction, GI upset, or serotonin syndrome, but not typically dry mouth. * **Dopaminergic receptors:** Blockade of D2 receptors (common in antipsychotics) leads to Extrapyramidal Symptoms (EPS) and hyperprolactinemia. * **GABA receptors:** These are inhibitory receptors in the CNS. Drugs acting here (like Benzodiazepines) cause sedation and anxiolysis, not peripheral autonomic side effects like xerostomia. **High-Yield Clinical Pearls for NEET-PG:** * **TCAs** are the biggest culprits of "Anti-SLUDGE" effects (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis—all of which are decreased). * **Amitriptyline** has the highest anticholinergic potency among TCAs. * **Management:** Patients are often advised to use sugarless gum or frequent sips of water. * **Contraindication:** Due to their muscarinic blockade, these drugs should be used with caution in patients with **narrow-angle glaucoma** and **benign prostatic hyperplasia (BPH)**.

Q: Which of the following drugs has the least anticholinergic side effects?

Desipramine. **Explanation:** The question tests your knowledge of the side effect profiles of **Tricyclic Antidepressants (TCAs)**. All options listed belong to the TCA class, which typically block muscarinic (M1), histamine (H1), and alpha-1 adrenergic receptors, leading to their characteristic side effect profile. **Why Desipramine is Correct:** TCAs are broadly divided into **Tertiary Amines** and **Secondary Amines**. * **Secondary Amines** (e.g., Desipramine, Nortriptyline) are metabolites of tertiary amines. * They are more selective for inhibiting Norepinephrine reuptake and, crucially, have a **significantly lower affinity** for muscarinic, histaminic, and alpha-adrenergic receptors compared to their parent compounds. * **Desipramine** is the most potent norepinephrine reuptake inhibitor among TCAs and possesses the **least anticholinergic and sedative activity** in this group. **Why Other Options are Incorrect:** * **A, C, and D (Clomipramine, Imipramine, Trimipramine):** These are all **Tertiary Amines**. Tertiary amines are potent inhibitors of both Serotonin and Norepinephrine reuptake but also have a high affinity for muscarinic receptors. This results in significant anticholinergic effects such as dry mouth, blurred vision, urinary retention, and constipation. Among these, **Amitriptyline** (not listed) and **Clomipramine** are often cited as having the highest anticholinergic potency. **High-Yield NEET-PG Pearls:** 1. **Most Anticholinergic TCA:** Amitriptyline. 2. **Least Anticholinergic/Least Sedating TCA:** Desipramine. 3. **Least Arrhythmogenic/Safest in Elderly:** Nortriptyline (a secondary amine with a better safety profile). 4. **Drug of Choice for OCD:** Clomipramine (due to high serotonin selectivity). 5. **TCA Overdose Triad:** Coma, Convulsions, and Cardiac arrhythmias (prolonged QRS/QT intervals). The antidote for cardiotoxicity is Sodium Bicarbonate.

Q: Which of the following drugs belongs to the NaSSA group?

Mirtazapine. **Explanation:** **Mirtazapine** is the correct answer as it is the prototype drug of the **NaSSA** (Noradrenergic and Specific Serotonergic Antidepressant) class. ### Why Mirtazapine is correct: Mirtazapine works through a unique dual mechanism: 1. **Alpha-2 ($\alpha_2$) Antagonism:** It blocks presynaptic $\alpha_2$ autoreceptors (on noradrenergic neurons) and heteroreceptors (on serotonergic neurons). This "disinhibits" the neurons, leading to increased release of both Norepinephrine and Serotonin. 2. **Specific Serotonergic Action:** It blocks **$5-HT_2$** and **$5-HT_3$** receptors. By blocking these, it directs serotonin to specifically stimulate the **$5-HT_1A$** receptor, which mediates antidepressant effects while avoiding side effects like anxiety ($5-HT_2$) or nausea ($5-HT_3$). ### Why other options are incorrect: * **Amoxetine (Atomoxetine):** A selective **NRI** (Norepinephrine Reuptake Inhibitor) primarily used in ADHD. * **Duloxetine & Venlafaxine:** These belong to the **SNRI** (Serotonin-Norepinephrine Reuptake Inhibitor) class. They work by inhibiting the reuptake transporters (SERT and NET) rather than blocking $\alpha_2$ receptors. ### High-Yield Clinical Pearls for NEET-PG: * **Side Effect Profile:** Mirtazapine is a potent **$H_1$ blocker**, leading to significant **sedation** and **weight gain**. * **Clinical Utility:** It is the drug of choice for depressed patients suffering from **insomnia** and **underweight/anorexia**. * **Sexual Dysfunction:** Unlike SSRIs, Mirtazapine has a very low incidence of sexual dysfunction due to its $5-HT_2$ blockade. * **The "California Rocket Fuel":** A high-yield combination of Venlafaxine + Mirtazapine used for treatment-resistant depression.

Q: Neuroleptics cause hyperprolactinemia by blocking the effect of which neurotransmitter on pituitary lactotropes?

Dopamine. **Explanation:** The correct answer is **Dopamine**. **Mechanism of Action:** In the normal physiological state, dopamine acts as the primary **Prolactin Inhibiting Factor (PIF)**. It is secreted by the tuberoinfundibular pathway of the hypothalamus and acts on **D2 receptors** located on the pituitary lactotropes to tonicly inhibit prolactin secretion. Neuroleptics (antipsychotics) work by blocking D2 receptors. When these drugs block D2 receptors in the tuberoinfundibular pathway, the inhibitory effect of dopamine is lost, leading to disinhibition of lactotropes and a subsequent rise in serum prolactin levels (**Hyperprolactinemia**). **Analysis of Incorrect Options:** * **Glycine:** An inhibitory neurotransmitter primarily found in the spinal cord and brainstem; it does not regulate prolactin. * **Acetylcholine:** While involved in various central pathways, it does not play a primary role in the tonic inhibition of prolactin. * **Serotonin:** Generally has a stimulatory effect on prolactin release (via 5-HT receptors), but it is not the neurotransmitter blocked by neuroleptics to cause this specific side effect. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Features:** Hyperprolactinemia manifests as galactorrhea, gynecomastia, amenorrhea, and infertility. * **Drug Specifics:** Typical antipsychotics (e.g., Haloperidol) and the atypical antipsychotic **Risperidone** are most notorious for causing hyperprolactinemia. * **Exceptions:** **Aripiprazole** (a partial D2 agonist) and **Quetiapine** are less likely to cause significant prolactin elevation. * **Treatment:** If a drug must be used to treat hyperprolactinemia, dopamine agonists like **Cabergoline** or Bromocriptine are preferred.

Q: Which of the following medications is known to cause seizures as a side effect?

Clozapine. **Explanation:** **Clozapine** is the correct answer because it is well-documented for its dose-dependent risk of lowering the seizure threshold. It is an atypical (second-generation) antipsychotic reserved for treatment-resistant schizophrenia. The risk of seizures is approximately 1% at doses below 300 mg/day but increases significantly to about 5% at doses above 600 mg/day. This pro-convulsant effect is thought to be due to its potent antagonistic action at multiple receptors, particularly its effect on GABAergic and glutamatergic neurotransmission. **Incorrect Options:** * **Olanzapine:** While structurally related to clozapine, it has a much lower risk of seizures. Its primary side effects are significant weight gain and metabolic syndrome. * **Aripiprazole:** This is a partial D2 agonist with a very low seizure profile. It is generally considered weight-neutral and is less likely to cause sedation or extrapyramidal symptoms (EPS). * **Amisulpride:** A substituted benzamide that selectively blocks D2/D3 receptors. It is not typically associated with seizures; its main concerns are hyperprolactinemia and QTc prolongation. **High-Yield Clinical Pearls for NEET-PG:** 1. **Clozapine Monitoring:** The most feared side effect is **agranulocytosis** (requires mandatory ANC monitoring), but seizures and **myocarditis** are also critical life-threatening risks. 2. **Management:** If a patient on clozapine develops seizures, the dose should be reduced, and an anticonvulsant (usually **Valproate**) is added. 3. **Other Pro-convulsant Drugs in Psychiatry:** **Bupropion** (antidepressant) is the other high-yield drug known for causing seizures, especially in patients with eating disorders (bulimia/anorexia). 4. **Sialorrhea:** Clozapine is unique for causing excessive salivation (hypersalivation) despite its anticholinergic profile.

Q: Which of the following is NOT a side effect of depression?

Flupenthixol. **Explanation:** The question asks which drug is **NOT** associated with causing depression as a side effect. **1. Why Flupenthixol is the correct answer:** Flupenthixol is a thioxanthene neuroleptic (antipsychotic). While high doses are used to treat schizophrenia, **low doses (0.5–3 mg/day)** have a unique **antidepressant and anxiolytic effect**. Unlike many other antipsychotics that can cause "neuroleptic-induced deficit syndrome" (mimicking depression), low-dose flupenthixol is specifically indicated for the management of psychogenic depression and depressive neurosis. Therefore, it is a treatment for, rather than a cause of, depression. **2. Analysis of Incorrect Options (Drugs that cause depression):** * **Propranolol:** Beta-blockers, particularly lipophilic ones like propranolol, can cross the blood-brain barrier and are well-documented to cause depressive symptoms, fatigue, and sleep disturbances. * **Oral Contraceptives (OCPs):** Hormonal fluctuations caused by OCPs (specifically the progestogen component) are associated with mood swings and clinical depression in susceptible individuals due to interference with tryptophan metabolism. * **L-dopa:** While used for Parkinson’s disease, L-dopa can cause a wide range of psychiatric side effects, including depression, anxiety, and psychosis, as it alters dopamine levels in the mesolimbic pathway. **NEET-PG High-Yield Pearls:** * **Other drugs causing depression:** Reserpine (depletes monoamines), Interferon-alpha, Isotretinoin, and Corticosteroids. * **Reserpine** is the classic historical example used to support the "Monoamine Hypothesis" of depression. * **Flupenthixol** is often used in clinical practice for "masked depression" or depression with psychosomatic symptoms.

Q: Which of the following SSRIs has a sedating property?

Paroxetine. ### Explanation **Correct Option: C. Paroxetine** Paroxetine is unique among Selective Serotonin Reuptake Inhibitors (SSRIs) because it possesses significant **antimuscarinic (anticholinergic) activity**. This mild blockade of cholinergic receptors, combined with its weak inhibition of the norepinephrine transporter, results in a **sedating effect**. Consequently, it is often prescribed for patients with depression associated with significant anxiety or insomnia. **Analysis of Incorrect Options:** * **A. Fluoxetine:** Known as the most "activating" SSRI. It has a long half-life and can cause insomnia and agitation; therefore, it is typically administered in the morning. * **B. Mianserin:** While it is highly sedating, it is a **Tetracyclic Antidepressant (TeCA)**, not an SSRI. It acts as an alpha-2 antagonist. * **D. Clomipramine:** This is a **Tricyclic Antidepressant (TCA)**, specifically a potent serotonin reuptake inhibitor used in OCD. While sedating, it does not belong to the SSRI class. **High-Yield Clinical Pearls for NEET-PG:** * **Weight Gain:** Paroxetine is the SSRI most commonly associated with weight gain and the highest risk of **discontinuation syndrome** due to its short half-life and lack of active metabolites. * **Teratogenicity:** Paroxetine is generally avoided in pregnancy as it is linked to **fetal cardiac malformations** (ASD/VSD). * **Drug Interactions:** It is a potent inhibitor of the **CYP2D6** enzyme. * **Fluvoxamine:** Another SSRI that can be sedating (often used in OCD), but Paroxetine remains the classic textbook answer for sedating SSRIs.

Question 1

Dry mouth during antidepressant therapy is caused by blockade of which receptors?

Accepted Answer

Muscarinic acetylcholine receptors

Answer

Serotonergic receptors

Answer

Dopaminergic receptors

Answer

GABA receptors

Question 2

Which of the following drugs has the least anticholinergic side effects?

Accepted Answer

Desipramine

Answer

Clomipramine

Answer

Imipramine

Answer

Trimipramine

Question 3

Which of the following drugs belongs to the NaSSA group?

Accepted Answer

Mirtazapine

Answer

Amoxetine

Answer

Duloxetine

Answer

Venlafaxine

Question 4

Which of the following statements is NOT true for the therapy with lithium?

Accepted Answer

Sodium ion is a specific antidote for lithium clearance.

Answer

It is used in bipolar disorder.

Answer

Amiloride is useful in treating lithium-induced diabetes insipidus.

Answer

Regular measurements of blood concentration of lithium are necessary.

Question 5

Neuroleptics cause hyperprolactinemia by blocking the effect of which neurotransmitter on pituitary lactotropes?

Accepted Answer

Dopamine

Answer

Glycine

Answer

Acetylcholine

Answer

Serotonin

Question 6

Which of the following medications is known to cause seizures as a side effect?

Accepted Answer

Clozapine

Answer

Olanzapine

Answer

Aripiprazole

Answer

Amisulpride

Question 7

Which of the following is NOT a side effect of depression?

Accepted Answer

Flupenthixol

Answer

Propranolol

Answer

Oral contraceptives

Answer

L-dopa

Question 8

Which of the following SSRIs has a sedating property?

Accepted Answer

Paroxetine

Answer

Fluoxetine

Answer

Mianserin

Answer

Clomipramine

Question 9

Which drug can act as an antagonist of Haloperidol?

Accepted Answer

Ropinirole

Answer

Clozapine

Answer

Imipramine

Answer

Pimozide

Question 10

Cardiac conduction defects seen with Tricyclic antidepressants are due to which mechanism?

Accepted Answer

Both norepinephrine reuptake inhibition and antimuscarinic action on the heart

Answer

Norepinephrine and serotonin reuptake inhibition

Answer

Antimuscarinic action on the heart

Answer

Only norepinephrine reuptake inhibition

Drugs in Psychiatric Disorders — MCQs

Drugs in Psychiatric Disorders — MCQs

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