Drugs in Psychiatric Disorders Practice Questions

Q: Which of the following is a selective 5-HT reuptake blocker?

Fluoxetine. ### Explanation **Correct Answer: C. Fluoxetine** **Mechanism of Action:** Fluoxetine is a prototype **Selective Serotonin Reuptake Inhibitor (SSRI)** [1, 3]. It works by specifically inhibiting the serotonin transporter (SERT) at the presynaptic terminal, thereby increasing the concentration of serotonin (5-HT) in the synaptic cleft [2]. Unlike older antidepressants, SSRIs have minimal affinity for adrenergic, histaminergic, or cholinergic receptors, leading to a better side-effect profile [3]. **Analysis of Incorrect Options:** * **A. Desipramine:** This is a secondary amine **Tricyclic Antidepressant (TCA)**. It is highly selective for inhibiting the reuptake of **Norepinephrine (NE)** rather than Serotonin [3]. * **B. Amitriptyline:** A tertiary amine **TCA**. It is a non-selective inhibitor that blocks the reuptake of both **Serotonin and Norepinephrine (SNRI-like action)**. It also possesses significant anticholinergic and sedative properties [1, 3]. * **D. Dothiepin (Dosulepin):** Another **TCA** similar to amitriptyline. It inhibits the reuptake of both NE and 5-HT and is known for its high cardiotoxicity in overdose [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** SSRIs (like Fluoxetine) are the first-line treatment for Depression, OCD, Panic Disorder, Social Phobia, and Post-Traumatic Stress Disorder (PTSD) [3]. * **Longest Half-life:** Fluoxetine has the longest half-life among SSRIs (due to its active metabolite, norfluoxetine), making it the least likely to cause "discontinuation syndrome" [2]. * **Side Effects:** The most common side effects of SSRIs include **GI upset (nausea/diarrhea)** and **sexual dysfunction** (delayed ejaculation) [2]. * **Serotonin Syndrome:** Always monitor for this when SSRIs are combined with MAO inhibitors; a "washout period" of 2–5 weeks is required when switching between them.

Q: Vilazodone is a:

Serotonin partial agonist and reuptake inhibitor (SPARI). **Explanation:** **Vilazodone** is a unique antidepressant classified as a **Serotonin Partial Agonist and Reuptake Inhibitor (SPARI)**. Its mechanism of action is dual: 1. **Inhibition of Serotonin Reuptake:** It inhibits the serotonin transporter (SERT), similar to SSRIs, increasing synaptic serotonin levels. 2. **5-HT1A Receptor Partial Agonism:** It acts as a partial agonist at the presynaptic and postsynaptic 5-HT1A receptors. This dual action is thought to result in a faster clinical onset and potentially fewer sexual side effects compared to traditional SSRIs. **Analysis of Incorrect Options:** * **Option A (SSRI):** While Vilazodone does inhibit serotonin reuptake, the term SSRI is reserved for drugs like Fluoxetine or Sertraline, which lack direct receptor agonist activity. * **Option B (SARI):** Serotonin Antagonist and Reuptake Inhibitors (e.g., **Trazodone, Nefazodone**) primarily block 5-HT2 receptors rather than acting as 5-HT1A partial agonists. * **Option C (SNRI):** SNRIs (e.g., **Venlafaxine, Duloxetine**) inhibit the reuptake of both Serotonin and Norepinephrine. Vilazodone has no significant effect on norepinephrine reuptake. **High-Yield Clinical Pearls for NEET-PG:** * **Vortioxetine** is another related drug, often called a "Serotonin Modulator and Stimulator" (SMS), which acts as a 5-HT1A agonist and 5-HT3 antagonist. * **Side Effects:** Vilazodone is most commonly associated with GI upset (diarrhea, nausea). * **Key Advantage:** It is noted for having a **lower incidence of sexual dysfunction** and weight gain compared to SSRIs, making it a preferred choice in specific patient profiles.

Q: Which antidepressant has no anticholinergic effects?

Fluoxamine. **Explanation:** The correct answer is **Fluvoxamine** (Option C). **1. Why Fluvoxamine is correct:** Fluvoxamine belongs to the **Selective Serotonin Reuptake Inhibitors (SSRIs)** class. Unlike older antidepressants, SSRIs specifically inhibit the reuptake of serotonin (5-HT) with minimal to no affinity for muscarinic (cholinergic), alpha-adrenergic, or histaminergic receptors. Consequently, they are devoid of classical anticholinergic side effects such as dry mouth, blurred vision, urinary retention, and constipation. **2. Why other options are incorrect:** * **Imipramine & Amitriptyline (Options A & D):** These are **Tricyclic Antidepressants (TCAs)**. TCAs are notorious for blocking muscarinic receptors. Amitriptyline is, in fact, the most potent anticholinergic among the TCAs. * **Mianserin (Option B):** This is an atypical (tetracyclic) antidepressant. While it has significantly fewer anticholinergic effects compared to TCAs, it still possesses some mild antimuscarinic activity, unlike SSRIs which have none. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC):** SSRIs (like Fluvoxamine, Fluoxetine, Sertraline) are the first-line treatment for Depression, OCD, Panic Disorder, and Social Phobia due to their superior safety profile. * **Side Effects of SSRIs:** While they lack anticholinergic effects, they commonly cause **GI upset (nausea/diarrhea)** and **sexual dysfunction** (delayed ejaculation). * **TCA Overdose Triad:** Coma, Convulsions, and Cardiotoxicity (due to sodium channel blockade). * **Fluvoxamine Specific:** It is particularly noted for its efficacy in **Obsessive-Compulsive Disorder (OCD)**.

Q: Which of the following is a mood-stabilizing drug?

Lithium. ### Explanation **Correct Answer: A. Lithium** **Mechanism and Role:** Lithium is the "gold standard" mood stabilizer used primarily in the treatment of **Bipolar Affective Disorder (BPAD)**. It is effective in treating acute mania and is the drug of choice for the long-term prophylaxis of both manic and depressive episodes. Its mechanism involves the inhibition of the **Inositol Monophosphatase (IMPase) pathway**, which depletes intracellular phosphatidylinositol 4,5-bisphosphate (PIP2), thereby dampening overactive neuronal signaling. **Analysis of Incorrect Options:** * **B. Fluoxetine:** This is a **Selective Serotonin Reuptake Inhibitor (SSRI)**. It is an antidepressant used for Major Depressive Disorder and Panic Disorder. In BPAD, using antidepressants alone can potentially trigger a "switch" into mania. * **C. Amitriptyline:** This is a **Tricyclic Antidepressant (TCA)**. It inhibits the reuptake of Norepinephrine and Serotonin. Like Fluoxetine, it is used for depression, not as a primary mood stabilizer. * **D. Haloperidol:** This is a high-potency **First-Generation Antipsychotic (Typical Antipsychotic)**. While it is used to manage acute agitation in manic episodes due to its D2 receptor antagonism, it does not possess the prophylactic mood-stabilizing properties required to prevent future episodes. **High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Index:** Lithium has a very **narrow therapeutic index** (0.5–1.2 mEq/L). Monitoring is essential. * **Teratogenicity:** Use in pregnancy is associated with **Ebstein’s Anomaly** (atrialization of the right ventricle). * **Side Effects:** Common issues include fine tremors, polyuria (Nephrogenic Diabetes Insipidus), and hypothyroidism. * **Other Mood Stabilizers:** Valproate (often preferred for rapid cycling), Carbamazepine, and Lamotrigine.

Q: What is the specific antagonist for benzodiazepines?

Flumazenil. ### Explanation **Correct Option: A. Flumazenil** Flumazenil is a specific **competitive antagonist** at the benzodiazepine (BZD) binding site on the **GABA-A receptor** complex [1], [3]. It effectively reverses the sedative, psychomotor, and anticonvulsant effects of benzodiazepines [1]. It is the drug of choice for managing BZD overdose and for reversing sedation induced during anesthesia or diagnostic procedures [4]. **Analysis of Incorrect Options:** * **B. Alprazolam:** This is a short-to-intermediate acting **benzodiazepine agonist** used primarily for anxiety and panic disorders [2]. It would worsen, rather than antagonize, BZD toxicity. * **C. Di-isopropyl phenol:** This is the chemical name for **Propofol**, a rapid-acting intravenous anesthetic agent. It acts by enhancing GABAergic neurotransmission but at a different site than BZDs. * **D. Cremophor EL:** This is a **polyoxyethylated castor oil** used as a pharmaceutical vehicle (solvent) to solubilize hydrophobic drugs like Diazepam (in older formulations) or Paclitaxel. It is associated with hypersensitivity reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Flumazenil blocks the BZD site but does *not* antagonize the effects of Barbiturates, Ethanol, or General Anesthetics, as they bind to different sites on the GABA receptor [1]. * **Half-life:** Flumazenil has a very short half-life (~1 hour). Because most BZDs have a longer duration of action, **re-sedation** can occur, necessitating repeated doses or an infusion. * **Contraindication:** It should be avoided in patients with a history of seizures or those with mixed tricyclic antidepressant (TCA) overdose, as it can precipitate **refractory seizures** by removing the protective anticonvulsant effect of the BZD [3]. * **Z-drugs:** Flumazenil also reverses the effects of non-benzodiazepine hypnotics like Zolpidem, Zaleplon, and Eszopiclone [1].

Q: Which of the following SSRIs does NOT affect the blood levels of other drugs?

Sertraline. ### Explanation The primary reason SSRIs (Selective Serotonin Reuptake Inhibitors) affect the blood levels of other drugs is their ability to inhibit **Cytochrome P450 (CYP450)** enzymes in the liver. When these enzymes are inhibited, the metabolism of co-administered drugs (like warfarin, TCAs, or beta-blockers) decreases, leading to increased plasma concentrations and potential toxicity. **1. Why Sertraline is the Correct Answer:** **Sertraline** (along with Citalopram and Escitalopram) is known for having **minimal to no inhibitory effect** on CYP450 isoenzymes. Because it does not significantly interfere with the metabolic pathways of other medications, it has a very low potential for clinically significant drug-drug interactions. This makes it a preferred choice in elderly patients or those on multiple medications (polypharmacy). **2. Why the Other Options are Incorrect:** * **Fluoxetine:** A potent inhibitor of **CYP2D6** and **CYP3A4**. It has a very long half-life and significantly raises the levels of drugs like haloperidol and propranolol. * **Fluvoxamine:** A potent inhibitor of **CYP1A2** and **CYP2C19**. It significantly increases the levels of theophylline and warfarin. * **Paroxetine:** A highly potent inhibitor of **CYP2D6**. It can interfere with its own metabolism and significantly increase the levels of tricyclic antidepressants (TCAs). **Clinical Pearls for NEET-PG:** * **Safest SSRIs (Lowest Drug Interactions):** Sertraline, Citalopram, Escitalopram. * **Most Potent CYP2D6 Inhibitors:** Fluoxetine and Paroxetine. * **Longest Half-life:** Fluoxetine (due to its active metabolite, norfluoxetine), which requires a 5-week washout period before starting an MAOI to avoid **Serotonin Syndrome**. * **Drug of Choice (DOC):** SSRIs are the first-line treatment for Depression, OCD, Panic Disorder, and Social Phobia.

Q: All of the following are hallucinogens, except?

Methylphenidate. **Explanation:** The correct answer is **Methylphenidate**. **1. Why Methylphenidate is the correct answer:** Methylphenidate is a **CNS stimulant** that primarily acts by increasing the synaptic concentration of dopamine and norepinephrine through the inhibition of their reuptake (similar to cocaine). It is the first-line pharmacological treatment for **Attention Deficit Hyperactivity Disorder (ADHD)** and is also used in Narcolepsy. Unlike hallucinogens, it does not typically induce perceptual distortions or hallucinations at therapeutic doses. **2. Why the other options are incorrect:** * **LSD (Lysergic Acid Diethylamide):** A potent "classic" hallucinogen and a 5-HT2A receptor agonist. It causes profound alterations in sensory perception and "synesthesia" (seeing sounds/hearing colors). * **Phencyclidine (PCP):** Also known as "Angel Dust," it is a **dissociative anesthetic** that acts as an NMDA receptor antagonist. It is notorious for causing hallucinations, agitation, and vertical/horizontal nystagmus. * **Mescaline:** A naturally occurring alkaloid derived from the Peyote cactus. Like LSD, it acts primarily on serotonin receptors to produce hallucinogenic effects. **Clinical Pearls for NEET-PG:** * **Psilocybin** (Magic mushrooms) and **DMT** are other common classic hallucinogens. * **Ketamine** is a "dissociative" hallucinogen similar to PCP (NMDA antagonist). * **Adverse effect of Methylphenidate:** Growth suppression in children (requires "drug holidays") and insomnia. * **Antidote for Hallucinogen Overdose:** Generally supportive care; Benzodiazepines are used for agitation or "bad trips."

Q: Which of the following is a monoamine oxidase inhibitor?

Phenelzine. **Explanation:** **Phenelzine** is the correct answer as it is a **non-selective, irreversible Monoamine Oxidase Inhibitor (MAOI)**. It works by inhibiting both MAO-A and MAO-B enzymes, thereby increasing the synaptic concentrations of norepinephrine, serotonin, and dopamine. While effective for atypical depression, it is considered a second-line agent due to its side effect profile and dietary restrictions. **Analysis of Incorrect Options:** * **Amitriptyline:** This is a **Tricyclic Antidepressant (TCA)**. It primarily inhibits the reuptake of serotonin and norepinephrine. It is also known for its significant anticholinergic and sedative properties. * **Benztropine:** This is a **centrally acting anticholinergic** (muscarinic antagonist). In psychiatry, it is primarily used to treat Extrapyramidal Side Effects (EPS) caused by antipsychotics, such as acute dystonia or parkinsonism. * **Clonazepam:** This is a **Benzodiazepine** that acts as a GABA-A receptor modulator. It is used as an anxiolytic, hypnotic, and antiepileptic, but it does not inhibit the MAO enzyme. **High-Yield Clinical Pearls for NEET-PG:** * **Cheese Reaction:** Patients on non-selective MAOIs (like Phenelzine) must avoid tyramine-rich foods (aged cheese, red wine). Tyramine displaces stored norepinephrine, leading to a **hypertensive crisis**. * **Drug Interactions:** MAOIs should never be combined with SSRIs or Pethidine due to the risk of **Serotonin Syndrome**. * **Washout Period:** A 14-day gap is required when switching between MAOIs and other antidepressants to allow for enzyme regeneration. * **Selective MAO-B Inhibitor:** Remember **Selegiline**, used primarily in Parkinson’s disease.

Question 1

Which of the following is a RIMA?

Accepted Answer

brofaromine

Answer

escitalopram

Answer

selegiline

Answer

dapoxetine

Question 2

Which of the following is a selective 5-HT reuptake blocker?

Accepted Answer

Fluoxetine

Answer

Desipramine

Answer

Amitriptyline

Answer

Dothiepin

Question 3

Vilazodone is a:

Accepted Answer

Serotonin partial agonist and reuptake inhibitor (SPARI)

Answer

Selective serotonin reuptake inhibitor (SSRI)

Answer

Serotonin antagonist and reuptake inhibitor (SARI)

Answer

Serotonin-norepinephrine reuptake inhibitor (SNRI)

Question 4

Which antidepressant has no anticholinergic effects?

Accepted Answer

Fluoxamine

Answer

Imipramine

Answer

Mianserin

Answer

Amitriptyline

Question 5

Which of the following is a mood-stabilizing drug?

Accepted Answer

Lithium

Answer

Fluoxetine

Answer

Amitriptyline

Answer

Haloperidol

Question 6

What is the specific antagonist for benzodiazepines?

Accepted Answer

Flumazenil

Answer

Alprazolam

Answer

Di-isopropyl phenol

Answer

Cremophor EL

Question 7

All of the following are true about Clozapine EXCEPT?

Accepted Answer

It has a lesser potency in blocking 5-HT2 than the D2 receptor.

Answer

It can cause agranulocytosis.

Answer

It has more affinity to D4 receptors compared to D2 receptors.

Answer

It is an atypical antipsychotic agent.

Question 8

Which of the following SSRIs does NOT affect the blood levels of other drugs?

Accepted Answer

Sertraline

Answer

Fluoxetine

Answer

Fluvoxamine

Answer

Paroxetine

Question 9

All of the following are hallucinogens, except?

Accepted Answer

Methylphenidate

Answer

LSD

Answer

Phenylcyclidine

Answer

Mescaline

Question 10

Which of the following is a monoamine oxidase inhibitor?

Accepted Answer

Phenelzine

Answer

Amitriptyline

Answer

Benztropine

Answer

Clonazepam

Drugs in Psychiatric Disorders — MCQs

Drugs in Psychiatric Disorders — MCQs

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