Antiepileptics and CNS Drugs (Antipsychotics, Antidepressants, Sedatives) MCQs

Pharmacology · 222 free questions with answers & explanations.

1. A 28-year-old woman with bipolar disorder on valproate plans a pregnancy. The teratological risk specific to valproate that her neurologist must counsel her about is:
2. Clozapine has the lowest risk of extrapyramidal side effects among antipsychotics. The pharmacological basis is:
3. A patient on phenytoin for epilepsy is started on fluconazole for oral candidiasis. Three days later she develops diplopia, nystagmus, and ataxia. The most likely mechanism is:
4. Which benzodiazepine is safest in patients with liver disease and requires NO hepatic metabolism?
5. A patient on an SSRI for depression develops fever, muscle rigidity, diaphoresis, and hyperreflexia 2 days after adding tramadol for back pain. This represents:
6. A patient on valproate and lamotrigine develops severe rash and mucositis consistent with Stevens-Johnson syndrome. The pharmacokinetic interaction responsible is:
7. Clozapine has the lowest risk of tardive dyskinesia among antipsychotics despite being highly efficacious in refractory schizophrenia. Which pharmacological property best explains this?
8. A patient with bipolar disorder on lithium develops coarse tremors, confusion, and ECG changes. Serum lithium level is 2.8 mEq/L. Which early pharmacological intervention reduces lithium absorption from the gut in acute toxicity?
9. Which antidepressant is contraindicated in a patient taking tramadol for chronic pain, due to risk of serotonin syndrome, while also being an inhibitor of CYP2D6?
10. Levetiracetam's anticonvulsant mechanism is unique among antiepileptics. Which molecular target mediates its action?
11. A 32-year-old woman with treatment-resistant depression is started on augmentation with lithium. After 3 weeks she develops coarse tremor, polyuria, polydipsia, and mild cognitive slowing. Lithium toxicity is most likely because of concurrent use of:
12. Clozapine's superior efficacy in treatment-resistant schizophrenia compared to typical antipsychotics is partly attributed to its unique receptor pharmacology. Which of the following BEST describes the key differentiating feature?
13. Sodium valproate inhibits seizures through multiple mechanisms. Which of the following mechanisms is considered most responsible for its broad-spectrum efficacy across absence, tonic-clonic, and myoclonic seizures?
14. A patient on a high-dose SSRI develops confusion, agitation, hyperthermia, tachycardia, diaphoresis, hyperreflexia, and clonus after adding linezolid for a post-operative infection. This adverse drug interaction is most precisely explained by:
15. Perampanel, a third-generation antiepileptic, has a novel mechanism compared to classical agents. It is best classified as:
16. Carbamazepine causes autoinduction of its own metabolism through which cytochrome P450 enzyme, and what is the clinical consequence?
17. The mechanism underlying clozapine-induced agranulocytosis is BEST explained by:
18. A patient on phenelzine (MAOI) for refractory depression is inadvertently given pethidine for post-operative pain. The life-threatening interaction is mediated by:
19. Lacosamide, a newer antiepileptic, exerts its unique mechanism of action by:
20. The D2 receptor partial agonism of aripiprazole means that in a dopamine-depleted (hypo-dopaminergic) state, aripiprazole will:
21. Perampanel, a newer antiepileptic approved for focal and generalised tonic-clonic seizures, exerts its effect by which unique mechanism not shared by any other currently marketed antiepileptic?
22. A patient with treatment-resistant depression fails multiple SSRIs and SNRIs. Pharmacogenomic testing reveals ultrarapid CYP2C19 metabolizer status. This genotype most directly explains poor response to which antidepressant?
23. Brexpiprazole, approved for adjunctive treatment of major depression and schizophrenia, differs from aripiprazole at the D2 receptor in which pharmacologically important way?
24. Lacosamide's antiepileptic mechanism involves 'slow inactivation' of sodium channels rather than the 'fast inactivation' promoted by carbamazepine. Which molecular feature of lacosamide facilitates this slow-inactivation selectivity?
25. A patient with absence epilepsy is started on ethosuximide. The anti-absence mechanism of ethosuximide involves blockade of which specific ion channel, and in which neuronal tissue is this effect most relevant?
26. Clozapine is unique among antipsychotics in its efficacy in treatment-resistant schizophrenia. Beyond D2 blockade, which receptor binding profile best explains both its superior efficacy and its metabolic/cardiovascular side-effect profile?
27. A 35-year-old woman with bipolar disorder and epilepsy is being started on lamotrigine. Her physician warns her about the risk of Stevens-Johnson syndrome and advises slower titration. This risk is significantly increased when lamotrigine is co-administered with which drug?
28. A 42-year-old woman on phenelzine (irreversible MAO inhibitor) for refractory depression eats a meal of aged cheese and develops hypertensive crisis with severe headache. The mechanism of this interaction is best described as:
29. Pregabalin and gabapentin share a structural analogy with GABA but do not act on GABA receptors. Their anticonvulsant and analgesic mechanism involves which molecular target?
30. Perampanel, approved as adjunctive therapy in focal and generalized seizures, acts via a mechanism distinct from all prior antiepileptics. Its mechanism is:
31. A patient on clozapine develops severe agranulocytosis. The pharmacogenomic marker most strongly associated with clozapine-induced agranulocytosis in Caucasians is:
32. A 45-year-old woman with treatment-resistant MDD is prescribed esketamine nasal spray (Spravato). Its rapid antidepressant effect, occurring within hours, is mechanistically attributed to:
33. Aripiprazole's unique receptor pharmacology that distinguishes it from first and most second-generation antipsychotics is its action as a:
34. A patient on carbamazepine for trigeminal neuralgia develops a maculopapular rash 3 weeks after starting therapy. HLA genotyping prior to treatment could have predicted this risk. The HLA allele associated with carbamazepine-induced Stevens–Johnson syndrome in Han Chinese is:
35. A patient on valproate for epilepsy develops thrombocytopenia and elevated serum ammonia without liver failure. Which mechanism best explains the hyperammonemia?
36. Lacosamide is a newer antiepileptic that differs from carbamazepine despite both acting on sodium channels. Which property is unique to lacosamide?
37. A patient with treatment-resistant depression is started on ketamine infusions. Which intracellular signalling cascade mediates the rapid antidepressant effect observed within hours — distinct from the mechanism of traditional antidepressants?
38. A patient homozygous for CYP2C19*17 alleles (ultrarapid metabolizer) is started on escitalopram for depression. Compared to an extensive metabolizer, what is most likely to occur?
39. A 32-year-old woman with bipolar disorder on valproate develops polycystic ovarian morphology, irregular menses, hyperandrogenism, and weight gain. Which pharmacological property of valproate most likely explains these endocrine effects?
40. A patient on clozapine develops fever, tachycardia, diaphoresis, extrapyramidal rigidity, and a creatine kinase of 12,000 U/L. The treating physician suspects neuroleptic malignant syndrome (NMS). Paradoxically, clozapine causes NMS through which mechanism despite its low D2 binding affinity?
41. Bupropion is approved for major depressive disorder and smoking cessation. Its antidepressant mechanism is DISTINCT from SSRIs and SNRIs because it acts primarily as:
42. Perampanel, a newer antiepileptic approved as adjunctive therapy for focal and generalized tonic-clonic seizures, acts by which unique mechanism that distinguishes it from all older antiepileptics?
43. Perampanel, a newer antiepileptic, has a unique mechanism among approved antiepileptics in that it:
44. Aripiprazole's ability to reduce both positive and negative symptoms of schizophrenia without weight gain is best attributed to its receptor pharmacology profile of:
45. A depressed patient who is a CYP2D6 ultrarapid metabolizer is given nortriptyline at standard doses. The expected clinical consequence is:
46. Sodium oxybate (GHB, gamma-hydroxybutyrate) is approved for cataplexy in narcolepsy. Its mechanism of action relevant to this indication involves:
47. A 32-year-old on valproate for bipolar disorder becomes pregnant. Apart from neural tube defects, the teratogenic concern specifically linked to valproate's inhibition of histone deacetylase (HDAC) relates to:
48. A 32-year-old woman with focal epilepsy poorly controlled on levetiracetam is found to carry the SCN1A p.Arg1648Cys variant (gain-of-function mutation). The BEST pharmacological choice to add is:
49. Clozapine's superior efficacy in treatment-resistant schizophrenia is attributed to which receptor pharmacology profile distinguishing it from other second-generation antipsychotics?
50. A patient on a therapeutic dose of an SSRI develops fever 40°C, muscle rigidity, myoclonus, hyperreflexia, and diarrhea 2 hours after adding tramadol for pain. This presentation is best managed with:
51. Valproate inhibits multiple pharmacological targets. Which of the following mechanisms contributes MOST to its broad-spectrum antiepileptic activity including absence seizures?
52. A woman of childbearing age with juvenile myoclonic epilepsy is counselled against valproate. The preferred alternative levetiracetam exerts its antiepileptic effect through which unique mechanism?
53. In treatment-resistant depression, augmentation with aripiprazole is preferred over olanzapine. The pharmacological rationale relates to aripiprazole's unique receptor profile, which includes:
54. A patient on carbamazepine for trigeminal neuralgia develops a severe maculopapular rash. Pharmacogenomic testing reveals HLA-B*15:02 positivity. This allele predicts risk for which adverse reaction?
55. Clozapine's superior efficacy in treatment-resistant schizophrenia despite relatively low D2 receptor occupancy is best explained by which property?
56. Brexanolone (allopregnanolone) is approved for postpartum depression. Its mechanism of action primarily involves:
57. A patient on carbamazepine for epilepsy develops hyponatremia with serum sodium of 126 mEq/L. What is the mechanism underlying this adverse effect?
58. Which pharmacogenomic variant is most strongly associated with carbamazepine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis in Southeast Asian populations?
59. Valproate inhibits which enzyme involved in GABA metabolism, thereby contributing to its anticonvulsant action?
60. Clozapine's unique efficacy in treatment-resistant schizophrenia is best explained by its receptor binding profile compared to typical antipsychotics. Which characteristic is most pharmacologically distinctive?
61. Sodium valproate inhibits which enzyme to elevate brain GABA levels, contributing to its antiepileptic effect?
62. A patient started on clozapine develops fever, rigidity, altered consciousness and a creatine kinase of 8000 U/L on day 3. The most appropriate immediate treatment after discontinuing clozapine is:
63. Lamotrigine exerts its primary antiepileptic mechanism by:
64. The atypical antipsychotic with the lowest propensity for extrapyramidal side effects and highest risk of agranulocytosis is:
65. Bupropion is used for depression and smoking cessation. Its pharmacological mechanism is:
66. A 28-year-old woman with treatment-resistant major depression undergoes intranasal esketamine therapy. The mechanism of its rapid antidepressant effect is:
67. A patient with focal epilepsy poorly controlled on carbamazepine is found to be a CYP3A4 ultrarapid inducer due to genetic variation. The MOST pharmacologically accurate explanation for therapeutic failure is:
68. A 35-year-old woman with treatment-resistant depression is started on a MAO-B selective inhibitor as augmentation, and later develops hypertensive crisis after eating aged cheese. The mechanism is:
69. Sodium valproate's teratogenicity (causing neural tube defects) is best attributed to which molecular mechanism?
70. A patient on clozapine develops severe metabolic syndrome. The receptor most responsible for clozapine-induced weight gain and hyperphagia is:
71. The anticonvulsant mechanism of perampanel — a newer anti-epileptic drug — is unique because it targets:
72. A patient on haloperidol develops sustained muscle spasm of the neck, oculogyric crisis, and arching of the back three days after starting the drug. This is best classified as:
73. Lamotrigine exerts its antiepileptic effect primarily by:
74. A 35-year-old woman with depression develops serotonin syndrome after her SSRI dose was increased and she was concurrently prescribed tramadol for back pain. Which triad of findings is most characteristic of serotonin syndrome?
75. The 'anticonvulsant hypersensitivity syndrome' occurring with aromatic antiepileptics (phenytoin, carbamazepine, phenobarbitone) is thought to be mediated by toxic accumulation of:
76. Valproate is teratogenic due to neural tube defects. Its mechanism of teratogenicity involves:
77. Clozapine requires mandatory weekly white blood cell monitoring due to which potentially fatal side effect?
78. Bupropion is used in smoking cessation and depression. Its mechanism that distinguishes it from SSRIs and SNRIs is:
79. Clozapine causes agranulocytosis as a serious adverse effect. The mechanism most accepted for this idiosyncratic toxicity involves:
80. A patient on phenytoin develops gingival hyperplasia. The most accepted cellular mechanism is:
81. Lamotrigine's primary mechanism of antiepileptic action is:
82. Which benzodiazepine is preferred for status epilepticus via the intravenous route due to its rapid onset and relatively long duration compared to others by this route?
83. A 28-year-old woman with bipolar disorder is started on lamotrigine. Valproate is added for better mood control. The dose of lamotrigine must be REDUCED by 50% because valproate:
84. Which antipsychotic is classified as a dopamine partial agonist at D2 receptors (dopamine system stabiliser) and also acts as a partial agonist at 5-HT1A receptors?
85. A patient taking phenelzine (an irreversible MAO inhibitor) for depression develops severe headache, hypertensive crisis, and palpitations after eating aged cheese. This is the 'cheese reaction.' Which enzyme substrate causes this by releasing norepinephrine from sympathetic terminals?
86. Zolpidem is preferred over diazepam for insomnia because it selectively acts on which GABA-A receptor subunit combination?
87. A patient on clozapine develops absolute neutrophil count (ANC) <500/mm3. Apart from stopping clozapine, which haematopoietic agent can be used to accelerate recovery of neutrophil count?
88. Lamotrigine's antiepileptic mechanism primarily involves:
89. A 40-year-old man taking valproate for epilepsy shows elevated serum ammonia with encephalopathy but near-normal liver enzymes. The most likely mechanism for this valproate-associated hyperammonemia is:
90. Clozapine is unique among antipsychotics in treating refractory schizophrenia but requires mandatory monitoring due to its most feared adverse effect. What agranulocytosis monitoring schedule is required?
91. A patient on phenytoin for generalised tonic-clonic seizures is started on rifampicin for pulmonary tuberculosis. What pharmacokinetic consequence is expected?
92. Which antidepressant mechanism best explains why mirtazapine causes weight gain and sedation more than most SSRIs?
93. A 28-year-old woman with a history of migraine, bipolar disorder, and epilepsy is considering starting valproate. The prescriber must counsel her primarily about which teratogenic risk?
94. Clozapine's unique antipsychotic efficacy in treatment-resistant schizophrenia is attributed to its distinct receptor pharmacology. Which profile best explains its superiority over typical antipsychotics?
95. Bupropion is prescribed as an antidepressant. Its primary mechanism of action is:
96. Lamotrigine is used as a mood stabiliser in bipolar disorder and as an antiepileptic. Its primary mechanism of action is:
97. A patient on long-term benzodiazepine therapy abruptly stops the drug. The life-threatening withdrawal complication that can occur and the mechanism behind it is:
98. A 28-year-old woman with juvenile myoclonic epilepsy is started on valproate. The drug's most important mechanism relevant to myoclonic seizures involves:
99. A patient on clozapine for treatment-resistant schizophrenia develops a WBC count of 2800/mm³. The mechanism of clozapine-induced agranulocytosis involves:
100. Lamotrigine is used as add-on therapy for partial seizures and also in bipolar depression. Its mechanism shared across both indications is:
101. A patient taking fluoxetine for depression is inadvertently given tramadol for pain. He develops agitation, clonus, hyperthermia, and diaphoresis within 30 minutes. The mechanism is:
102. A 55-year-old man with Parkinson's disease on levodopa-carbidopa develops sudden onset uncontrollable movements of his limbs 2 hours after his morning dose. This side effect is termed:
103. Sodium oxybate (gamma-hydroxybutyrate/GHB) is used in narcolepsy with cataplexy. Its mechanism for improving cataplexy and sleep consolidation involves:
104. A patient with treatment-resistant depression fails two adequate SSRI trials. She is started on ketamine infusion. The mechanism of ketamine's rapid antidepressant effect (within hours) is distinct from SSRIs because:
105. A 32-year-old woman with focal epilepsy is on carbamazepine. She becomes pregnant. The neurologist is most concerned about a specific teratogenic risk. Which neural tube defect is most strongly associated with carbamazepine use during the first trimester?
106. Clozapine is the only antipsychotic consistently effective in treatment-resistant schizophrenia. Its superior efficacy has been linked to its receptor binding profile. Which receptor occupancy pattern distinguishes clozapine from typical antipsychotics?
107. A 50-year-old man on phenytoin for epilepsy develops symptoms of cerebellar ataxia, nystagmus, and confusion. His plasma phenytoin level is 32 mcg/mL. The treating physician reduces the dose. This toxicity occurs at a sub-lethal level primarily because phenytoin exhibits:
108. A 28-year-old woman with bipolar disorder is started on lamotrigine. Her dermatologist notes she also uses an oral contraceptive pill containing ethinyl estradiol and levonorgestrel. The pharmacokinetic consequence of this combination relevant to the psychiatrist is:
109. Buspirone is prescribed for generalised anxiety disorder. Unlike benzodiazepines, buspirone does not cause sedation, dependence, or enhance GABA-A function. Its primary mechanism of action is:
110. Perampanel, approved for adjunctive treatment of focal and generalized tonic-clonic seizures, acts by a uniquely distinct mechanism compared to all other antiepileptic drugs. Its mechanism is:
111. Clozapine's superior efficacy in treatment-resistant schizophrenia is partially attributed to its receptor binding profile. Which receptor combination best distinguishes clozapine from other second-generation antipsychotics?
112. A patient on phenytoin develops double vision, nystagmus, and ataxia. The plasma level is in the toxic range. Phenytoin's concentration-dependent kinetics (saturation kinetics) means that a small dose reduction will:
113. Brexpiprazole and cariprazine are classified as dopamine 'partial agonists' at D2 receptors. The therapeutic advantage of partial agonism over full antagonism (e.g., haloperidol) at D2 receptors includes:
114. A 32-year-old woman on a therapeutic dose of lithium (serum level 0.9 mEq/L) for bipolar disorder develops coarse tremor, slurred speech, and confusion after starting a new drug. Which drug most likely precipitated lithium toxicity?
115. Valproic acid is the broadest spectrum antiepileptic. It achieves this via multiple mechanisms. Which mechanism is responsible for its efficacy in absence seizures specifically?
116. Ketamine, a dissociative anaesthetic and antidepressant, produces its rapid antidepressant effect (within hours) by a mechanism distinct from monoamine-based antidepressants. The most widely accepted mechanism is:
117. Buspirone is an anxiolytic with no abuse potential, unlike benzodiazepines. Its mechanism of action is:
118. A 35-year-old woman with bipolar disorder is started on valproate. After 3 weeks she develops vomiting, confusion, and her serum ammonia is markedly elevated. Liver function tests are normal. This adverse effect of valproate is most likely due to:
119. Clozapine's superior efficacy in treatment-resistant schizophrenia compared with typical antipsychotics is primarily attributed to its:
120. A patient taking an SSRI for depression is also prescribed tramadol for pain. Two days later he develops agitation, hyperthermia, diaphoresis, and clonus. The pathophysiological mechanism responsible is:
121. Lamotrigine is particularly useful in bipolar depression. Its primary mechanism of action in seizure control is:
122. Regarding benzodiazepine pharmacology, which of the following best explains why zolpidem has fewer anxiolytic and muscle-relaxant effects compared with diazepam despite acting at the same receptor complex?
123. A 28-year-old woman with bipolar disorder on valproate presents at 8 weeks gestation. Valproate's main teratogenic mechanism linked to neural tube defects involves:
124. Among second-generation antipsychotics, clozapine is uniquely effective for treatment-resistant schizophrenia. Which receptor binding profile best explains its superior efficacy while also accounting for its seizure-risk side effect?
125. A patient taking phenytoin for epilepsy is found to have zero-order (saturable) kinetics at therapeutic doses. A dose increase of 20% raises plasma levels disproportionately by 80%. Which pharmacokinetic feature of phenytoin explains this?
126. Which antidepressant mechanism is most associated with hypertensive crisis when tyramine-rich foods are ingested?
127. Midazolam, used for procedural sedation, is distinct from diazepam in clinical pharmacokinetics primarily because:
128. A 25-year-old woman with juvenile myoclonic epilepsy is started on sodium valproate. Which COMBINATION of mechanisms best explains its broad-spectrum antiseizure activity?
129. A 35-year-old man with treatment-resistant schizophrenia is started on clozapine. After 3 months, he develops neutropenia. The hematological monitoring protocol requires weekly CBCs for:
130. A patient with major depressive disorder is started on an SNRI. The mechanism by which SNRIs are effective involves:
131. A 28-year-old woman with epilepsy is being initiated on lamotrigine. The dose is titrated slowly when given with valproate because valproate:
132. An elderly patient on chlorpromazine for schizophrenia develops parkinsonian features and tardive dyskinesia after 18 months. The receptor mechanism MOST responsible for tardive dyskinesia is:
133. Carbamazepine is a potent inducer of CYP3A4 and also autoinduces its own metabolism. A patient with bipolar disorder stabilised on carbamazepine is started on oral contraceptives. Which clinical consequence is most likely?
134. Which antiepileptic drug acts by selectively binding to the SV2A (synaptic vesicle glycoprotein 2A) and is approved as adjunctive therapy for focal and generalised seizures with a favourable drug-interaction profile?
135. Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia. The life-threatening haematological adverse effect that necessitates mandatory periodic blood monitoring is:
136. A young man presents 12 hours after taking an overdose of a tricyclic antidepressant with prolonged QRS, hypotension and seizures. The most appropriate intervention to counteract cardiac toxicity is administration of:
137. Which benzodiazepine is preferred in elderly patients requiring anxiolysis because it does not undergo hepatic Phase I oxidative metabolism and has no active metabolites?
138. Sodium valproate has multiple mechanisms; which of the following is considered its PRIMARY mechanism of action in seizure control?
139. A patient with tardive dyskinesia develops this condition after prolonged use of a first-generation antipsychotic. The pathophysiological mechanism most widely accepted is:
140. Lamotrigine is effective in focal and generalised seizures including absence. Its primary mechanism is:
141. The unique antidepressant effect of mirtazapine compared to SSRIs is mediated through:
142. Levetiracetam has a novel mechanism of action that differs from all classic antiepileptics. It acts by:
143. Perampanel, approved as adjunctive therapy in partial-onset seizures, has a unique mechanism among antiepileptics. It acts as a selective non-competitive antagonist at which receptor?
144. A 35-year-old woman on valproate for epilepsy develops tremor, weight gain, and hair loss. These adverse effects are most likely related to which mechanism?
145. Which antipsychotic has the highest risk of causing QTc prolongation and sudden cardiac death, and is specifically contraindicated in patients with congenital long QT syndrome?
146. A patient taking phenytoin for epilepsy develops gingival hyperplasia. The mechanism underlying this adverse effect involves:
147. A patient on an SSRI for depression is started on tramadol for pain. Within 2 hours she develops agitation, diaphoresis, hyperthermia, and clonus. The most likely diagnosis and the primary receptor mechanism driving this syndrome is:
148. A patient with newly diagnosed focal epilepsy is started on lacosamide. Its unique mechanism of action compared to phenytoin involves:
149. The risk of Stevens-Johnson syndrome is significantly higher in patients carrying the HLA-B*1502 allele who are prescribed:
150. Clozapine's superior efficacy in treatment-resistant schizophrenia is best attributed to its relatively HIGH affinity for which receptor, compared to typical antipsychotics?
151. Which antidepressant mechanism is responsible for the 'cheese effect' (hypertensive crisis) seen when certain foods are consumed?
152. Midazolam is preferred over diazepam for procedural sedation in the ICU primarily because:
153. A 30-year-old man with schizophrenia on haloperidol develops involuntary rhythmic movements of the tongue and lips with grimacing, three years into treatment. These movements persist even after haloperidol is stopped. What is this adverse effect, and what is the most likely mechanism?
154. A 25-year-old woman with absence epilepsy is started on a drug that blocks T-type voltage-gated calcium channels in thalamic neurons, disrupting the 3 Hz spike-and-wave oscillations. Which drug is this?
155. A 45-year-old man with Parkinson's disease on levodopa-carbidopa develops wearing-off and on-off fluctuations after 5 years of therapy. His neurologist adds a peripheral COMT inhibitor to prolong the action of levodopa. Which drug is being added?
156. A 28-year-old woman on long-term lithium for bipolar disorder presents with polyuria producing 5 litres of urine per day, polydipsia, and a urine specific gravity of 1.001. Serum sodium is 148 mEq/L. Which mechanism explains this presentation?
157. A 32-year-old man with treatment-resistant depression is prescribed phenelzine, an irreversible MAO inhibitor. The patient is counselled on dietary restrictions. Which food combination poses the GREATEST risk of a hypertensive crisis for this patient?
158. A 35-year-old woman presents to the emergency department following deliberate ingestion of multiple diazepam tablets. She is drowsy but rousable, with a respiratory rate of 10/min. Which statement best describes the mechanism of action of the reversal agent used?
159. An epileptic patient on long-term phenytoin therapy develops coarse facial features, gum hypertrophy, and hirsutism. Blood levels are within the therapeutic range. These effects are best explained by which pharmacological property of phenytoin?
160. A 28-year-old woman with a seizure disorder is started on valproate. Which of the following best explains valproate's efficacy in absence seizures?
161. A 6-year-old child is brought with sudden-onset staring episodes lasting 5–10 seconds with eye blinking, occurring >20 times daily. EEG confirms 3 Hz spike-and-wave discharges. The drug of choice and its primary mechanism are:
162. A patient receiving carbamazepine for trigeminal neuralgia develops hyponatraemia with serum sodium of 128 mEq/L. The most likely mechanism is:
163. Lamotrigine is used as add-on therapy in a patient with partial seizures refractory to carbamazepine. Which statement about lamotrigine's pharmacology is CORRECT?
164. A patient in the ICU has been fitting continuously for 35 minutes despite two doses of IV lorazepam. What is the next appropriate pharmacological step and its mechanism?
165. Levetiracetam's unique mechanism of action distinguishes it from most other antiepileptics. It acts by:
166. Barbiturates differ from benzodiazepines in their mechanism of action at GABA-A receptors. The key difference is:
167. A patient reports difficulty sleeping and is prescribed zolpidem. Which statement correctly differentiates zolpidem (a Z-drug) from classical benzodiazepines?
168. A 40-year-old man on haloperidol for schizophrenia develops sustained upward deviation of the eyes with neck stiffness within 2 days of starting therapy. This acute reaction is best described as:
169. Clozapine is prescribed for a patient with treatment-resistant schizophrenia. The mandatory baseline investigation and the life-threatening adverse effect it monitors are:
170. A patient develops hyperthermia (40.5°C), generalised lead-pipe rigidity, autonomic instability, and elevated serum creatine kinase after starting a depot antipsychotic. The treatment of choice includes:
171. Which atypical antipsychotic has the LOWEST risk of causing extrapyramidal side effects (EPS) and tardive dyskinesia, and why?
172. A 25-year-old woman on fluoxetine for depression is also started on tramadol for post-operative pain. She develops agitation, clonus, hyperthermia, and diaphoresis. The most likely diagnosis and mechanism is:
173. A patient on phenelzine (an MAOI) for depression eats aged cheese and develops a severe hypertensive crisis. The correct explanation is:
174. A depressed patient is started on amitriptyline. Which adverse effect profile is MOST characteristic of tricyclic antidepressants compared to SSRIs?
175. A 32-year-old woman on lithium for bipolar disorder presents with coarse tremor, polyuria, and vomiting. Serum lithium is 1.9 mEq/L. The mechanism of lithium toxicity is best explained by:
176. Morphine produces analgesia primarily through which receptor and intracellular mechanism?
177. A patient is brought unconscious with pin-point pupils, respiratory rate 4/min, and a Glasgow Coma Scale of 6 after suspected fentanyl overdose. Naloxone is administered IV. Which property of naloxone is most relevant to repeat dosing?
178. Propofol is used for induction and maintenance of anaesthesia. Which statement about propofol is CORRECT?
179. Ketamine is described as producing 'dissociative anaesthesia'. Its primary mechanism and a unique clinical feature is:
180. Minimum Alveolar Concentration (MAC) is an important measure in inhalational anaesthesia. Which of the following DECREASES MAC?
181. Lignocaine (lidocaine) is used as a local anaesthetic. The mechanism by which it blocks nerve conduction is:
182. A patient receiving a bupivacaine epidural develops cardiovascular collapse with a wide-complex arrhythmia refractory to standard ACLS measures. The specific antidote is:
183. Levodopa is used in Parkinson's disease. Why is it combined with carbidopa?
184. A Parkinson's patient on levodopa-carbidopa for 6 years develops sudden random involuntary writhing movements of the limbs unrelated to dose timing. This phenomenon is termed:
185. A patient with Parkinson's disease is prescribed selegiline. Its mechanism and a specific dietary interaction to avoid are:
186. A patient with Parkinson's disease started on pramipexole (a dopamine agonist) reports episodes of falling asleep suddenly while driving without warning. This adverse effect is known as:
187. Regarding SSRIs, which statement best explains their delayed therapeutic onset (2–4 weeks) despite rapid serotonin reuptake inhibition?
188. A patient on clozapine for treatment-resistant schizophrenia develops fever, agranulocytosis, and drooling. The receptor most responsible for the drooling (sialorrhea) as an adverse effect of clozapine is:
189. Lamotrigine is the preferred antiepileptic in women of childbearing age partly due to lower teratogenicity than valproate. However, lamotrigine levels can drop significantly during pregnancy, requiring dose adjustment. The mechanism is:
190. A patient on a therapeutic dose of phenytoin develops nystagmus, ataxia, and mental slowing. Phenytoin has a narrow therapeutic window because of its saturable (zero-order) kinetics. Which pharmacokinetic principle best explains why small incremental doses cause disproportionately large rises in plasma phenytoin levels?
191. A 42-year-old woman on venlafaxine (SNRI) for major depressive disorder presents with severe hypertension, diaphoresis, and tachycardia after starting linezolid for VRE infection. The most appropriate immediate management is:
192. A pharmacogenomics consultation is requested for a 35-year-old woman with bipolar disorder about to start lamotrigine. Her HLA genotype is HLA-B*15:02. What is the clinical significance of this finding?
193. Clozapine is the gold-standard antipsychotic for treatment-resistant schizophrenia. Its superior efficacy is attributed to a unique receptor binding profile. Which receptor-binding characteristic differentiates clozapine from first-generation antipsychotics and accounts for its minimal extrapyramidal side effects?
194. Sodium valproate is metabolized to 4-en-valproic acid via beta-oxidation in the mitochondria. This metabolite is specifically responsible for which serious adverse effect?
195. A patient on phenytoin for seizures requires initiation of warfarin for atrial fibrillation. Two weeks later, the patient is found to have subtherapeutic INR despite adequate warfarin dosing. Subsequently, the patient is switched off phenytoin to levetiracetam. One week later, the patient presents with massive GI bleed and INR of 8. What is the mechanism?
196. A 28-year-old man with major depressive disorder is started on an SSRI but shows no response after 8 weeks at adequate dose. Genetic testing reveals he is a CYP2D6 ultra-rapid metabolizer. Which statement best explains his pharmacokinetic situation and guides the next therapeutic step?
197. Carbamazepine induces its own metabolism via CYP3A4 (autoinduction), resulting in lower plasma levels after the first few weeks of therapy. This is an example of which pharmacokinetic phenomenon?
198. A patient on clozapine develops absolute neutrophil count (ANC) of 450 cells/µL at week 8. According to pharmacovigilance monitoring guidelines, what is the appropriate management?
199. Sodium valproate's ability to inhibit GABA transaminase (GABA-T) results in increased synaptic GABA. However, its teratogenicity (neural tube defects) is mechanistically linked to:
200. A 28-year-old woman on venlafaxine 225 mg/day is started on tramadol for post-operative pain. She develops agitation, diaphoresis, hyperreflexia, clonus, and hyperthermia. The pathophysiological basis of this syndrome is:
201. Sodium valproate is effective across multiple seizure types. Its primary mechanism of action at the molecular level involves:
202. A patient on clozapine develops agranulocytosis. The mechanism underlying clozapine-induced agranulocytosis is best described as:
203. Lamotrigine is preferred over carbamazepine for focal epilepsy during pregnancy. The pharmacological basis for lamotrigine's teratogenic risk being lower is:
204. A 45-year-old patient on sertraline develops a hypertensive crisis after eating aged cheese. The explanation for this interaction involves:
205. Zolpidem is a non-benzodiazepine hypnotic that acts on GABA-A receptors. Compared to diazepam, zolpidem's selectivity is explained by its preferential binding to:
206. A patient on valproate for epilepsy develops tremor, weight gain, and elevated liver enzymes. Which mechanism explains valproate's hepatotoxicity?
207. Clozapine is the antipsychotic of choice for treatment-resistant schizophrenia. Its unique receptor profile compared with typical antipsychotics includes:
208. A patient on phenytoin for epilepsy shows zero-order kinetics at therapeutic doses. This is because:
209. Mirtazapine's mechanism of antidepressant action is best described as:
210. A patient develops sudden-onset fever, muscle rigidity, altered consciousness, and autonomic instability 48 hours after starting a high-potency antipsychotic. The pathophysiological mechanism of this syndrome involves:
211. Valproate is used across multiple seizure types. In addition to sodium channel blockade, it inhibits which enzyme that increases brain GABA levels?
212. Tardive dyskinesia (TD) is a late-onset movement disorder from antipsychotics. The FIRST-LINE approved pharmacological treatment for TD is:
213. Vigabatrin is an antiepileptic used for infantile spasms (West syndrome) and as adjunctive therapy for focal seizures. Its mechanism of action is:
214. A young woman with juvenile myoclonic epilepsy (JME) is treated with valproate but then becomes pregnant. Valproate is considered teratogenic. Its neural tube defect risk is linked to inhibition of which molecular mechanism?
215. Levetiracetam's mechanism of action in epilepsy is distinct from all other antiepileptics because it:
216. Lithium has a narrow therapeutic window (0.6–1.2 mEq/L). Which ion transport mechanism explains why NSAIDs increase lithium toxicity?
217. Cyclophosphamide requires hepatic activation to produce its active alkylating metabolite. It also causes a characteristic toxicity not shared by other alkylating agents when given without adequate hydration. What is this unique adverse effect and its causative metabolite?
218. Cisplatin causes dose-limiting nephrotoxicity. To prevent it, forced saline diuresis with intravenous hydration is mandatory. Which pharmacological property of cisplatin explains why it accumulates in renal proximal tubular cells?
219. Tigecycline is a glycylcycline antibiotic active against tetracycline-resistant organisms. Which resistance mechanisms overcome by tigecycline explain its expanded spectrum compared to earlier tetracyclines?
220. A patient with MRSA bacteraemia fails vancomycin therapy. Daptomycin is considered next. Daptomycin's bactericidal mechanism involves:
221. Which antifungal drug acts as a prodrug, is converted by fungal cytosine deaminase to 5-fluorouracil within fungal cells, and is used in combination with amphotericin B for cryptococcal meningitis?
222. A 35-year-old healthcare worker develops community-acquired pneumonia with atypical features: dry cough, headache, myalgia and patchy infiltrate on CXR with cold agglutinins positive. The drug of choice for the likely causative organism is: