Antidepressants: SSRIs and SNRIs — MCQs

10 questions

An SSRI antidepressant, such as fluoxetine, will be prescribed for an adult patient. You should advise him or her that two of the most likely side effects or adverse responses that may eventually occur at therapeutic blood levels are which of the following?

Which of the following is not an adverse effect of Escitalopram?

How do SSRIs alleviate symptoms of depression?

What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?

What is the most common gastrointestinal side effect of oral contraceptives?

Which of the following is a tricyclic antidepressant?

Which of the following is a selective norepinephrine reuptake inhibitor that can be used for the treatment of ADHD?

A patient on SSRI sertraline was also prescribed amitriptyline and subsequently developed serotonin toxicity. What is the likely treatment for serotonin toxicity?

Q10

Which of the following antidepressants is least likely to have sexual side effects?

Antidepressants: SSRIs and SNRIs Indian Medical PG Practice Questions and MCQs

Question 1: An SSRI antidepressant, such as fluoxetine, will be prescribed for an adult patient. You should advise him or her that two of the most likely side effects or adverse responses that may eventually occur at therapeutic blood levels are which of the following?

A. Sexual dysfunction and sleep disturbances (Correct Answer)
B. Sexual dysfunction and nausea
C. Headache and diarrhea
D. Tremor and weight gain

Explanation: ***Sexual dysfunction and sleep disturbances*** - **Sexual dysfunction** is one of the most common and persistent adverse effects of SSRIs, affecting 40-65% of patients and continuing throughout treatment at therapeutic levels [2], [3]. - **Sleep disturbances** (insomnia or altered sleep architecture) can persist during long-term SSRI therapy and are among the eventual side effects patients experience [1], [2], [3]. - Both effects are characteristic of chronic SSRI use and significantly impact patient compliance and quality of life. *Sexual dysfunction and nausea* - While **sexual dysfunction** is indeed very common and persistent, **nausea** is typically a transient side effect that occurs during the first 1-2 weeks of treatment and usually resolves with continued use [2]. - The question specifically asks about *eventual* occurrence at therapeutic levels over time, making nausea less appropriate as it is not a chronic issue. *Tremor and weight gain* - **Tremor** is not among the most common side effects of SSRIs and occurs less frequently than sexual dysfunction or sleep disturbances. - **Weight gain** can occur with some SSRIs (particularly paroxetine), but fluoxetine is actually considered weight-neutral or may even cause weight loss in some patients, making this combination less likely for fluoxetine specifically [1]. *Headache and diarrhea* - Both **headache** and **diarrhea** are common initial side effects when starting SSRIs but typically improve or resolve within the first few weeks of treatment [1]. - These are transient effects rather than eventual persistent side effects that characterize long-term therapeutic use.

Question 2: Which of the following is not an adverse effect of Escitalopram?

A. Sialorrhoea (Correct Answer)
B. Anorgasmia
C. Vivid dreams
D. Nausea

Explanation: ***Sialorrhoea*** - **Sialorrhoea** (excessive salivation) is generally *not* an adverse effect associated with **escitalopram** or other SSRIs; in fact, **dry mouth** is a more common side effect due to cholinergic blockade [2]. - SSRIs primarily act by increasing **serotonin** levels in the synaptic cleft, and this mechanism does not typically lead to overproduction of saliva. *Anorgasmia* - **Anorgasmia** (inability to achieve orgasm) is a well-known and common sexual adverse effect of **escitalopram** and other **SSRIs** [1, 2]. - This occurs due to increased serotonin activity in the brain, impacting neural pathways involved in sexual response. *Vivid dreams* - **Vivid dreams** or nightmares are a recognized neuropsychiatric side effect of **escitalopram** and other **SSRIs** [1, 3]. - This effect is thought to be related to changes in **REM sleep architecture** caused by serotonin modulation. *Nausea* - **Nausea** is a very common gastrointestinal adverse effect of **escitalopram**, especially during the initial phase of treatment [1]. - It results from increased serotonin activity in the **gastrointestinal tract**, where many serotonin receptors are located.

Question 3: How do SSRIs alleviate symptoms of depression?

A. By increasing synaptic serotonin levels (Correct Answer)
B. By inhibiting GABA receptors
C. By increasing norepinephrine degradation
D. By decreasing dopamine release

Explanation: ***By increasing synaptic serotonin levels*** - **Selective Serotonin Reuptake Inhibitors (SSRIs)** block the reabsorption (reuptake) of **serotonin** by neurons, leading to higher concentrations of serotonin in the synaptic cleft. - Increased **synaptic serotonin** availability is believed to enhance neuronal communication and mood regulation, thus alleviating symptoms of depression. *By inhibiting GABA receptors* - Inhibiting **GABA receptors** would typically lead to increased neuronal excitability, potentially worsening anxiety or causing seizures, rather than alleviating depression. - Medications that act on GABA receptors, such as **benzodiazepines**, are primarily used for anxiety and sedation, not as first-line antidepressants. *By increasing norepinephrine degradation* - Increasing **norepinephrine degradation** would reduce the levels of norepinephrine, a neurotransmitter associated with alertness and mood, which would likely worsen depressive symptoms. - Many antidepressants, such as **SNRIs**, aim to *increase* norepinephrine levels, not degrade them. *By decreasing dopamine release* - Decreasing **dopamine release** would likely lead to symptoms of anhedonia, lack of motivation, and other features of depression, or even extrapyramidal symptoms if significantly reduced. - **Dopamine** is often associated with reward and pleasure pathways, and increasing its availability can be beneficial in some forms of depression.

Question 4: What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?

A. Norepinephrine reuptake inhibition only
B. Anticholinergic effects on the heart
C. Both norepinephrine reuptake inhibition and anticholinergic effects on the heart (Correct Answer)
D. Direct membrane stabilizing effects only

Explanation: ***Both norepinephrine reuptake inhibition and anticholinergic effects on the heart*** - **Tricyclic antidepressants (TCAs)** block the reuptake of **norepinephrine**, which can lead to increased sympathetic tone on the heart and potentially **tachyarrhythmias** or other cardiac complications. - TCAs also have potent **anticholinergic effects**, blocking muscarinic receptors in the heart; this can increase **heart rate** and affect cardiovascular stability. - While **direct membrane stabilizing effects** (sodium channel blockade) are critical for **QRS widening and conduction delays**, the combination of norepinephrine reuptake inhibition and anticholinergic effects accounts for the broader spectrum of **TCA-induced cardiac toxicity** including tachycardia and hemodynamic instability. *Norepinephrine reuptake inhibition only* - While TCAs do inhibit norepinephrine reuptake contributing to tachycardia and increased sympathetic tone, this mechanism alone does not fully explain the breadth of cardiac effects seen with these drugs. - The **anticholinergic effects** play a significant additional role in altering cardiac function. *Anticholinergic effects on the heart* - While TCAs do exert anticholinergic effects that can impact heart rate and cardiovascular function, this mechanism alone fails to account for the additional contributions from **norepinephrine reuptake inhibition** to the overall cardiac toxicity. - The combination of both mechanisms is necessary for a complete understanding of **TCA-induced cardiac effects**. *Direct membrane stabilizing effects only* - This option refers to the **quinidine-like action** of TCAs, which involves blocking myocardial fast sodium channels, leading to a **prolonged QRS interval** and increased risk of **ventricular arrhythmias** and **conduction defects**. - While direct membrane stabilization is the **primary mechanism of TCA-induced conduction abnormalities** (QRS widening, heart blocks), the question asks for mechanisms of broader **cardiac toxicity**, which includes the combined effects of norepinephrine reuptake inhibition and anticholinergic actions on heart rate and hemodynamics.

Question 5: What is the most common gastrointestinal side effect of oral contraceptives?

A. Decreased appetite
B. Weight loss
C. Nausea (Correct Answer)
D. Constipation

Explanation: ***Nausea*** - **Nausea** is a very common gastrointestinal side effect of oral contraceptives, especially during the initial weeks of use, due to the **estrogen component**. - This side effect often **improves over time** as the body adjusts, or can be managed by taking the pill with food or at bedtime. *Weight loss* - Oral contraceptives are **not typically associated with weight loss**; in fact, some users may experience slight weight gain, although studies show no consistent significant effect. - Changes in weight are more often due to **fluid retention** rather than true fat loss. *Decreased appetite* - **Decreased appetite** is not a common side effect of oral contraceptives; rather, some individuals might experience an increased appetite due to hormonal fluctuations. - The hormonal effects on metabolism and appetite are **varied and not consistently demonstrated** to lead to decreased appetite. *Constipation* - **Constipation** is not a frequent gastrointestinal side effect of oral contraceptives; rather, some users may experience changes in bowel habits, but **diarrhea is more commonly reported** than constipation when GI issues occur. - Hormonal contraceptives primarily affect the gut through **estrogen and progestin**, leading to various effects, but constipation is not a predominant one.

Question 6: Which of the following is a tricyclic antidepressant?

A. Fluoxetine
B. Citalopram
C. Doxepin (Correct Answer)
D. Venlafaxine

Explanation: ***Doxepin*** - **Doxepin** is a **tricyclic antidepressant (TCA)** that inhibits the reuptake of **serotonin** and **norepinephrine**, and also has significant **histaminergic** and **cholinergic** blocking effects. - TCAs, including doxepin, are commonly used for treating **depression**, **anxiety**, and certain pain conditions. *Venlafaxine* - **Venlafaxine** is a **serotonin-norepinephrine reuptake inhibitor (SNRI)**, not a tricyclic antidepressant. - SNRIs selectively block the reuptake of both **serotonin** and **norepinephrine**, but lack the broad receptor affinity of TCAs. *Fluoxetine* - **Fluoxetine** is a **selective serotonin reuptake inhibitor (SSRI)**, which specifically targets serotonin reuptake. - SSRIs are generally considered a first-line treatment for depression due to a more favorable side effect profile compared to TCAs. *Citalopram* - **Citalopram** is also a **selective serotonin reuptake inhibitor (SSRI)**, much like fluoxetine. - It works by increasing the levels of **serotonin** in the brain by blocking its reuptake, differentiating it from tricyclic antidepressants.

Question 7: Which of the following is a selective norepinephrine reuptake inhibitor that can be used for the treatment of ADHD?

A. Reboxetine
B. Methylphenidate
C. Guanfacine
D. Modafinil
E. Atomoxetine (Correct Answer)

Explanation: ***Atomoxetine*** - **Atomoxetine** is a **selective norepinephrine reuptake inhibitor (SNRI)** that is **FDA-approved specifically for the treatment of ADHD** in children, adolescents, and adults. - It works by **selectively blocking the presynaptic norepinephrine transporter**, increasing norepinephrine availability in the prefrontal cortex and other brain regions involved in attention and impulse control. - Unlike stimulant medications, atomoxetine is **not a controlled substance** and is considered a first-line **non-stimulant option** for ADHD treatment. - It is particularly useful in patients with comorbid anxiety, tic disorders, or substance abuse concerns. *Reboxetine* - While **reboxetine** is technically a **selective norepinephrine reuptake inhibitor**, it is primarily used as an **antidepressant** and is **not approved for ADHD treatment**. - It has been investigated off-label for ADHD, but it is not a standard or recommended treatment option. - Reboxetine has **limited global availability** and has been withdrawn from many markets due to efficacy concerns. *Methylphenidate* - **Methylphenidate** is a **stimulant** medication that inhibits the reuptake of both **dopamine and norepinephrine**, making it **non-selective**. - It is a first-line treatment for ADHD, but its mechanism of action involves dual monoamine reuptake inhibition, not selective norepinephrine reuptake. *Guanfacine* - **Guanfacine** is an **alpha-2 adrenergic agonist**, not a norepinephrine reuptake inhibitor. - It works by stimulating postsynaptic alpha-2A receptors in the prefrontal cortex, which enhances prefrontal cortex function and improves attention and impulse control. *Modafinil* - **Modafinil** is a wakefulness-promoting agent with a **complex, non-selective mechanism** involving dopamine, norepinephrine, histamine, and orexin systems. - It is primarily used for **narcolepsy** and excessive daytime sleepiness, not as a primary ADHD treatment. - It is **not classified as a selective norepinephrine reuptake inhibitor**.

Question 8: Match the following drugs in Column A with their contraindications in Column B. | Column A | Column B | | :-- | :-- | | 1. Morphine | 1. QT prolongation | | 2. Amiodarone | 2. Thromboembolism | | 3. Vigabatrin | 3. Pregnancy | | 4. Estrogen preparations | 4. Head injury |

A. A-1, B-3, C-2, D-4
B. A-4, B-1, C-3, D-2 (Correct Answer)
C. A-3, B-2, C-4, D-1
D. A-2, B-4, C-1, D-3

Explanation: ***A-4, B-1, C-3, D-2*** - **Morphine** is contraindicated in **head injury** as it can increase intracranial pressure and mask neurological symptoms. - **Amiodarone** is contraindicated in patients with **QT prolongation** due to its risk of inducing more severe arrhythmias like Torsades de Pointes. - **Vigabatrin** is contraindicated during **pregnancy** due to its potential for teratogenicity and adverse effects on fetal development. - **Estrogen preparations** are contraindicated in patients with a history of **thromboembolism** due to their increased risk of blood clot formation. *A-1, B-3, C-2, D-4* - This option incorrectly matches **Morphine** with QT prolongation and **Estrogen preparations** with head injury, which are not their primary contraindications. - It also incorrectly links **Vigabatrin** with thromboembolism and **Amiodarone** with pregnancy. *A-3, B-2, C-4, D-1* - This choice incorrectly associates **Morphine** with pregnancy and **Vigabatrin** with head injury, which are not the most critical or direct contraindications. - It also misaligns **Amiodarone** with thromboembolism and **Estrogen preparations** with QT prolongation. *A-2, B-4, C-1, D-3* - This option incorrectly matches **Morphine** with thromboembolism and **Amiodarone** with head injury, which are not their most significant contraindications. - It also incorrectly links **Vigabatrin** with QT prolongation and **Estrogen preparations** with pregnancy.

Question 9: A patient on SSRI sertraline was also prescribed amitriptyline and subsequently developed serotonin toxicity. What is the likely treatment for serotonin toxicity?

A. Flumazenil
B. Cyproheptadine (Correct Answer)
C. L-Carnitine
D. Leucovorin
E. Naloxone

Explanation: ***Cyproheptadine*** - **Cyproheptadine** is a serotonin antagonist that can help reverse the effects of excessive serotonin in the central nervous system. - It works by blocking **serotonin 5-HT2A receptors**, which are implicated in the pathophysiology of serotonin toxicity. *Flumazenil* - **Flumazenil** is a benzodiazepine receptor antagonist used to reverse the effects of benzodiazepine overdose. - It has no role in the treatment of **serotonin toxicity**, as it does not affect serotonin pathways. *L-Carnitine* - **L-Carnitine** is a mitochondrial co-factor used in fatty acid metabolism, sometimes supplemented for certain metabolic disorders or muscle pain. - It does not have any direct action on **serotonin receptors** or the serotonin system, making it ineffective for serotonin toxicity. *Leucovorin* - **Leucovorin** (folinic acid) is used to counteract the effects of methotrexate toxicity or to enhance the effects of fluorouracil in chemotherapy. - It is not involved in modulating **neurotransmitter levels** or reversing the symptoms of serotonin toxicity. *Naloxone* - **Naloxone** is an opioid receptor antagonist used to reverse opioid overdose. - It has no effect on **serotonin receptors** or serotonergic pathways, making it ineffective for treating serotonin toxicity.

Question 10: Which of the following antidepressants is least likely to have sexual side effects?

A. Amitriptyline
B. Fluoxetine
C. Venlafaxine
D. Mirtazapine (Correct Answer)

Explanation: ***Mirtazapine*** - **Mirtazapine** is an atypical antidepressant (NaSSA - Noradrenergic and Specific Serotonergic Antidepressant) that works by blocking alpha-2 adrenergic receptors, enhancing serotonin and norepinephrine release [1]. - It has the **lowest incidence of sexual side effects** among antidepressants because it blocks 5-HT2 and 5-HT3 receptors while avoiding significant 5-HT1A stimulation, which is responsible for sexual dysfunction with SSRIs [1]. - It may even **improve libido** in some cases due to its unique receptor profile and histamine antagonism that can enhance sleep quality. *Amitriptyline* - **Amitriptyline** is a tricyclic antidepressant (TCA) with broad receptor actions, including anticholinergic and antihistaminic effects. - TCAs like amitriptyline can cause **sexual dysfunction** (including erectile dysfunction and decreased libido) due to their anticholinergic properties and effects on multiple neurotransmitter systems, though typically less severe than SSRIs. *Fluoxetine* - **Fluoxetine** is a selective serotonin reuptake inhibitor (SSRI), and while effective for depression, it is associated with a **high incidence of sexual side effects** (30-70% of patients) [2]. - These side effects include **decreased libido**, **anorgasmia**, and **erectile dysfunction**, caused by increased serotonergic activity at 5-HT2 receptors in areas regulating sexual function [2]. *Venlafaxine* - **Venlafaxine** is a serotonin-norepinephrine reuptake inhibitor (SNRI), increasing both serotonin and norepinephrine levels in the brain [1]. - Like SSRIs, SNRIs such as venlafaxine frequently cause **sexual dysfunction**, with common complaints including reduced libido and difficulty achieving orgasm due to enhanced serotonergic neurotransmission [1].

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