Principles of Psychopharmacology — MCQs
Variation in sensitivity of response to different doses of a drug in different individuals is obtained from?
Choose the correct options regarding the route of administration and bioavailability. A- Intravenous =1 B- 0.75< Oral <1 C-0.75 <IM ≤ 1 D- 0.75<SC ≤ 1 IM - Intramuscular SC- Subcutaneous
Which of the following actions is NOT associated with tricyclic antidepressants?
Which one of the following drugs has a narrow therapeutic range?
At toxic doses, zero-order kinetics is seen in which of the following substances?
Which statement best describes first-order kinetics in pharmacokinetics?
Which of the following best describes a Type B adverse drug reaction?
A 25-year-old medical student who failed his exam tells his friends, "I didn't want to pass anyway. The exam was poorly designed and doesn't test real clinical knowledge." This is an example of which defense mechanism?
Which among the following are defence mechanisms adopted when an individual is faced with problems or failures? I. Rationalization II. Regression III. Projection IV. Replacement Select the correct answer using the code given below :
Clozapine is used in:
Principles of Psychopharmacology Indian Medical PG Practice Questions and MCQs
Question 1: Variation in sensitivity of response to different doses of a drug in different individuals is obtained from?
- A. Dose-response relationship (Correct Answer)
- B. Therapeutic index
- C. Bioavailability
- D. Phase 1 clinical trials
Explanation: ***Dose-response relationship*** - The **dose-response relationship** (particularly the **graded dose-response curve**) describes how the magnitude of a drug's effect changes with different doses. - When plotted for different individuals or populations, these curves reveal **variation in sensitivity** through differences in potency (horizontal shift) and efficacy (maximum response). - This relationship helps characterize inter-individual variability in drug response and is the fundamental concept for understanding differential sensitivity. *Therapeutic index* - The **therapeutic index** is a measure of drug safety, representing the ratio between the toxic dose and the effective dose (TD50/ED50 or LD50/ED50). - It does not directly explain the variation in sensitivity to different doses among individuals, but rather provides information about the drug's overall safety margin. *Bioavailability* - **Bioavailability** refers to the fraction of an administered drug that reaches the systemic circulation unchanged. - While it influences the drug concentration at the site of action, it doesn't directly measure the variability in physiological response to that concentration among individuals. *Phase 1 clinical trials* - **Phase 1 clinical trials** are the first stage of testing a new drug in humans, primarily focusing on safety, dosage range, and pharmacokinetics in a small group of healthy volunteers. - While variability in response may be observed during these trials, they are not the *pharmacological concept* that describes this variation; rather, dose-response relationships are used to interpret findings from these trials.
Question 2: Choose the correct options regarding the route of administration and bioavailability. A- Intravenous =1 B- 0.75< Oral <1 C-0.75 <IM ≤ 1 D- 0.75<SC ≤ 1 IM - Intramuscular SC- Subcutaneous
- A. A and D
- B. A and C
- C. A, C, D (Correct Answer)
- D. A, B, D
Explanation: ***A, C, D*** - Intravenous (IV) administration has **100% bioavailability** because the drug enters the systemic circulation directly, bypassing any absorption barriers. - Intramuscular (IM) and subcutaneous (SC) routes generally have **high bioavailability**, often between 75% and 100%, as drugs are absorbed directly into the bloodstream without first-pass metabolism. *A and D* - While options A and D are correct, this choice is incomplete as option C is also a correct statement regarding bioavailability. - IM administration typically results in high systemic bioavailability, similar to SC, making its exclusion here incorrect. *A and C* - While options A and C are correct, this choice is incomplete as option D is also a correct statement regarding bioavailability. - Subcutaneous administration also generally results in high bioavailability, as absorption tends to be complete. *A, B, D* - While options A and D are correct, option B is typically incorrect for oral bioavailability. - Oral bioavailability of many drugs is often less than 0.75 (75%) due to factors like **first-pass metabolism** and incomplete absorption in the gastrointestinal tract.
Question 3: Which of the following actions is NOT associated with tricyclic antidepressants?
- A. Block 5-HT or NE reuptake
- B. Anticholinergic action
- C. MAO inhibition (Correct Answer)
- D. Causes sedation
Explanation: ***MAO inhibition*** - Tricyclic antidepressants (TCAs) primarily exert their effects by inhibiting the reuptake of **norepinephrine** and **serotonin**, not by inhibiting monoamine oxidase (MAO). - **MAO inhibitors** are a distinct class of antidepressants with a different mechanism of action and side effect profile. *Anticholinergic action* - Many TCAs have significant **anticholinergic effects**, blocking muscarinic receptors and leading to side effects like dry mouth, constipation, and blurred vision. - These effects contribute to the **adverse event profile** of TCAs, especially in elderly patients. *Block 5-HT or NE reuptake* - The primary mechanism of action of TCAs involves the **inhibition of serotonin (5-HT)** and **norepinephrine (NE) reuptake** into presynaptic neurons. - This action increases the concentration of these neurotransmitters in the **synaptic cleft**, thereby potentiating their effects. *Causes sedation* - TCAs frequently cause **sedation**, particularly the more histaminergic ones (e.g., amitriptyline, doxepin), due to their **histamine H1 receptor antagonism**. - This side effect can be beneficial for patients with insomnia but can be problematic for daytime functioning.
Question 4: Which one of the following drugs has a narrow therapeutic range?
- A. Propranolol
- B. Phenytoin (Correct Answer)
- C. Piroxicam
- D. Prazosin
Explanation: ***Phenytoin*** - **Phenytoin** has a **narrow therapeutic index**, meaning there is a small difference between the therapeutic and toxic doses. - This necessitates **therapeutic drug monitoring** to ensure effective treatment while avoiding adverse effects like nystagmus, ataxia, or gingival hyperplasia. *Propranolol* - **Propranolol** is a **beta-blocker** used for hypertension, angina, and arrhythmias, generally considered to have a wide therapeutic range. - While dose adjustments are common, routine therapeutic drug monitoring is typically **not required** due to its relatively safe profile at higher doses compared to drugs like phenytoin. *Piroxicam* - **Piroxicam** is a **nonsteroidal anti-inflammatory drug (NSAID)** with a relatively wide therapeutic window. - Its primary concerns are gastrointestinal and renal side effects rather than toxicity from a narrow therapeutic range. *Prazosin* - **Prazosin** is an **alpha-1 adrenergic blocker** used for hypertension and benign prostatic hyperplasia, and it generally has a wide therapeutic range. - The main concern with prazosin is **first-dose phenomenon** (orthostatic hypotension), which is an initial effect rather than toxicity from a narrow therapeutic window.
Question 5: At toxic doses, zero-order kinetics is seen in which of the following substances?
- A. Phenytoin (Correct Answer)
- B. Valproate
- C. Carbamazepine
- D. Penicillin
Explanation: ***Phenytoin*** - **Phenytoin** exhibits **zero-order kinetics** at toxic (saturating) doses because its metabolic enzymes become saturated, leading to a constant amount of drug eliminated per unit time rather than a constant fraction - This property makes its plasma concentration disproportionately increase with small dose adjustments once the enzymes are saturated, greatly increasing the risk of **toxicity** - Phenytoin is the **classic example** of capacity-limited metabolism due to saturation of hepatic enzymes (CYP2C9 and CYP2C19) *Penicillin* - Penicillin generally follows **first-order kinetics**, meaning a constant fraction of the drug is eliminated per unit time, and its elimination rate is proportional to its concentration - It is not commonly associated with zero-order kinetics even at higher doses, as its elimination pathways (renal excretion and metabolism) are typically not saturated within therapeutic or moderately toxic ranges *Valproate* - Valproate primarily follows **first-order kinetics** within its therapeutic range, with its elimination rate dependent on the drug concentration - While it can exhibit non-linear kinetics at very high concentrations due to protein binding saturation and enzyme saturation, it is less commonly cited as a classic example of zero-order kinetics compared to phenytoin *Carbamazepine* - Carbamazepine follows **first-order kinetics** within its therapeutic window - It undergoes **autoinduction** of its own metabolism, meaning that with continued dosing, its metabolic enzymes become more active, leading to increased elimination over time rather than saturation-induced zero-order kinetics
Question 6: Which statement best describes first-order kinetics in pharmacokinetics?
- A. Absorption of the drug is independent of the serum concentration
- B. Elimination of the drug is proportional to the serum concentration (Correct Answer)
- C. Absorption of the drug is proportional to the serum concentration
- D. Elimination of the drug is independent of the serum concentration
Explanation: ***Elimination of the drug is proportional to the serum concentration*** - In **first-order kinetics**, a **constant fraction** (or percentage) of the drug is eliminated per unit of time. - This means that as the **serum drug concentration** increases, the absolute amount of drug eliminated per unit time also increases proportionally. *Absorption of the drug is independent of the serum concentration* - Drug absorption is generally driven by factors like **concentration gradient**, surface area, and blood flow, and while it can be influenced by drug concentration, this statement does not define first-order kinetics of *elimination*. - This statement is not the primary characteristic distinguishing first-order from zero-order kinetics regarding drug disposition. *Elimination of the drug is independent of the serum concentration.* - This describes **zero-order kinetics**, where a **constant amount** of drug is eliminated per unit of time, regardless of the serum concentration. - In zero-order kinetics, the elimination rate becomes saturated, so the elimination process cannot keep up with higher drug concentrations. *Absorption of the drug is proportional to the serum concentration* - While drug absorption can be proportional to the concentration (especially through passive diffusion), first-order kinetics specifically refers to the **elimination phase** of pharmacokinetics. - The rate of absorption can be a complex process and is not the defining characteristic for distinguishing first-order from zero-order *elimination*.
Question 7: Which of the following best describes a Type B adverse drug reaction?
- A. Augmented effect of drug
- B. Effect seen on chronic use of drug
- C. Delayed effect of drug
- D. Unpredictable bizarre reaction (Correct Answer)
Explanation: ***Unpredictable bizarre reaction*** - Type B reactions are **unpredictable**, **bizarre**, and not directly related to the drug's known pharmacological actions. - They often involve **immunological reactions** or genetic predispositions, such as allergies or idiosyncratic responses. *Augmented effect of drug* - This describes a **Type A** adverse drug reaction, which is predictable and results from an **exaggerated pharmacological effect** of the drug. - It is typically dose-dependent and can be managed by adjusting the dosage. *Effect seen on chronic use of drug* - This description can apply to several types of adverse reactions, but it commonly relates to **Type C (chronic) reactions**, where effects occur only after prolonged exposure. - These reactions might be due to **cumulative toxicity** or adaptive changes in the body. *Delayed effect of drug* - This aligns with **Type D (delayed) adverse drug reactions**, which manifest long after the drug exposure has ended or after a period of latency. - Examples include **carcinogenesis** or teratogenesis, occurring months or years later.
Question 8: A 25-year-old medical student who failed his exam tells his friends, "I didn't want to pass anyway. The exam was poorly designed and doesn't test real clinical knowledge." This is an example of which defense mechanism?
- A. Denial
- B. Projection
- C. Displacement
- D. Rationalization (Correct Answer)
Explanation: ***Rationalization*** - **Rationalization** involves constructing a logical justification for actions or attitudes that otherwise would be unacceptable, thereby avoiding feelings of guilt or shame. - The man in the scenario uses logical reasons to explain his actions, preventing him from feeling guilty about them. *Denial* - **Denial** is a defense mechanism where a person refuses to accept or acknowledge a reality or facts of a situation, usually a painful or threatening one. - In this case, the man is not denying his actions but rather finding reasons to excuse them. *Projection* - **Projection** is when an individual attributes their own unacceptable thoughts, feelings, or qualities to another person. - The man is creating excuses for his own behavior, not attributing his feelings or actions to someone else. *Displacement* - **Displacement** involves redirecting unacceptable urges or feelings from their original target to a less threatening one. - The man is not shifting his emotions to a different object or person; instead, he is justifying his own actions.
Question 9: Which among the following are defence mechanisms adopted when an individual is faced with problems or failures? I. Rationalization II. Regression III. Projection IV. Replacement Select the correct answer using the code given below :
- A. I, III and IV
- B. I, II and III (Correct Answer)
- C. I, II and IV
- D. II, III and IV
Explanation: ***I, II and III*** - **Rationalization**, **Regression**, and **Projection** are all classic defense mechanisms described in psychoanalytic theory. - These mechanisms are unconscious strategies used by the **ego** to reduce anxiety and protect the self from unacceptable thoughts or feelings, particularly when an individual faces problems or failures. *I, III and IV* - This option correctly identifies Rationalization and Projection, but incorrectly includes **Replacement**. - While "replacement" might refer to a form of **displacement** in some contexts, it is not a standard, recognized defense mechanism in the classic psychoanalytic framework. *I, II and IV* - This option correctly identifies Rationalization and Regression, but incorrectly includes **Replacement**. - **Replacement** is not a standard defense mechanism; instead, individuals might experience **displacement** where feelings are redirected to a safer target. *II, III and IV* - This option includes Regression and Projection, but misses **Rationalization** while incorrectly including **Replacement**. - **Rationalization** is a very common defense mechanism involving creating logical but false justifications for actions or beliefs.
Question 10: Clozapine is used in:
- A. Depression
- B. Resistant schizophrenia (Correct Answer)
- C. Mania
- D. Delirium
Explanation: **Explanation:** **Clozapine** is an atypical (second-generation) antipsychotic and is considered the **gold standard** for the management of **Treatment-Resistant Schizophrenia (TRS)**. 1. **Why Option B is Correct:** Resistance in schizophrenia is defined as a lack of satisfactory clinical improvement despite the use of adequate doses of at least two different antipsychotics (including one atypical) for a duration of 6–8 weeks each. Clozapine is uniquely effective in these cases due to its complex receptor profile (low D2 affinity, high 5-HT2A, D4, and alpha-adrenergic blockade). It is the only antipsychotic proven to reduce suicidal behavior in schizophrenic patients. 2. **Why Other Options are Incorrect:** * **A. Depression:** First-line treatments are SSRIs/SNRIs. While some atypicals (like Quetiapine or Aripiprazole) are used as adjuncts in resistant depression, Clozapine is not used due to its side-effect profile. * **C. Mania:** Acute mania is treated with Lithium, Valproate, or standard antipsychotics (e.g., Olanzapine, Risperidone). Clozapine is reserved only for ultra-resistant cases, not as a standard indication. * **D. Delirium:** Low-dose Haloperidol is the drug of choice. Clozapine is contraindicated in delirium because its strong anticholinergic properties can worsen the confusional state. **High-Yield Clinical Pearls for NEET-PG:** * **Agranulocytosis:** The most dreaded side effect (occurs in ~1%). Mandatory **WBC monitoring** is required (weekly for the first 6 months). * **Seizures:** Clozapine carries a dose-dependent risk of seizures. * **Sialorrhea:** Paradoxical hypersalivation is a common, bothersome side effect. * **Myocarditis:** A rare but fatal side effect; monitor for tachycardia and chest pain. * **Metabolic Syndrome:** High risk of weight gain and diabetes (similar to Olanzapine).
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