NAPLEX Quiz: Adverse Reactions

What this quiz covers

This quiz focuses on Adverse Reactions, giving you a quick way to practice the rules, question types, and explanations that matter most for NAPLEX.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Continue lithium and ibuprofen; counsel to restrict fluids to reduce polyuria
2. Hold lithium and advise urgent evaluation for lithium toxicity; recommend avoiding nonsteroidal anti-inflammatory drugs and notify the prescriber to use an alternative analgesic and recheck lithium level and renal function (correct answer)
3. Stop quetiapine because it is the most likely cause of elevated lithium concentration
4. Increase lithium to 600 mg by mouth three times daily to overcome reduced efficacy from ibuprofen

Explanation: This question tests management of lithium toxicity from drug interactions. The patient's polyuria, polydipsia, tremor, elevated lithium level, and increased creatinine after starting ibuprofen indicates lithium toxicity, as NSAIDs reduce renal lithium clearance by inhibiting prostaglandin synthesis. The correct answer (B) appropriately holds lithium, recommends urgent evaluation, avoids NSAIDs, and ensures proper monitoring. Option A dangerously continues both drugs and restricts fluids which could worsen toxicity. Option C incorrectly blames quetiapine which doesn't significantly affect lithium levels. Option D shows dangerous misunderstanding by increasing lithium dose. NSAIDs can increase lithium levels by 20-60% within days; safer alternatives include acetaminophen or aspirin (with caution). When NSAIDs are necessary, reduce lithium dose prophylactically by 20-25% and monitor levels within 4-5 days.

Question 2

1. Quetiapine causing lithium level elevation through CYP3A4 inhibition
2. Hydrochlorothiazide increasing lithium concentrations leading to lithium toxicity (correct answer)
3. Lithium causing acute anaphylaxis with tremor and nausea
4. Hydrochlorothiazide causing serotonin syndrome

Explanation: This question tests the recognition of lithium toxicity from drug interactions affecting renal clearance. The key patient-specific factor is the recent addition of hydrochlorothiazide, which reduces lithium excretion leading to elevated levels (1.9 mEq/L) and symptoms like tremor, nausea, and slurred speech. Option B is the best choice because it identifies hydrochlorothiazide as the cause of lithium toxicity, requiring discontinuation or dose adjustment of lithium with monitoring. Option A is incorrect as quetiapine does not inhibit CYP3A4 or elevate lithium, option C is wrong because lithium does not cause anaphylaxis, and option D is suboptimal as hydrochlorothiazide does not induce serotonin syndrome. A clinical pearl is that thiazides can increase lithium levels by 25-40% via sodium depletion and reduced clearance. A decision framework for lithium therapy involves monitoring levels (target 0.6-1.2 mEq/L) with any diuretic or NSAID addition, holding doses if toxic, and ensuring hydration to prevent recurrence.

Question 3

1. Discontinue lisinopril and replace with losartan because ACE inhibitors commonly cause gynecomastia
2. Switch spironolactone to eplerenone and monitor potassium and renal function (correct answer)
3. Add testosterone therapy and continue spironolactone without changes
4. Increase spironolactone to 50 mg daily to reduce breast tenderness over time

Explanation: This question tests the management of spironolactone-induced gynecomastia in heart failure patients. The key patient-specific factor is the development of gynecomastia and breast tenderness after months on spironolactone, due to its anti-androgenic effects in a male patient with heart failure. Option B is the best choice because switching to eplerenone, a selective aldosterone antagonist, maintains heart failure benefits while reducing endocrine side effects like gynecomastia, with monitoring for hyperkalemia. Option A is incorrect as ACE inhibitors like lisinopril do not cause gynecomastia, and option C is wrong because adding testosterone is not standard and may have risks. Option D is suboptimal as increasing spironolactone would worsen symptoms. A clinical pearl is that spironolactone causes gynecomastia in up to 10% of men due to estrogenic activity, whereas eplerenone has lower incidence. In heart failure therapy, if endocrine effects occur, switch to eplerenone while ensuring potassium and renal monitoring to balance efficacy and tolerability.

Question 4

1. Avoid alcohol during metronidazole therapy and for at least 3 days after the last dose (correct answer)
2. Increase alcohol intake gradually to build tolerance while taking metronidazole
3. Take metronidazole only with grapefruit juice to reduce flushing
4. Stop oral contraceptives while taking metronidazole to prevent this reaction

Explanation: This question tests counseling to prevent disulfiram-like reactions from metronidazole-alcohol interactions. The key patient-specific factor is the patient's consumption of wine while on metronidazole, leading to flushing, headache, palpitations, and vomiting due to aldehyde dehydrogenase inhibition. Option A is the best choice because avoiding alcohol during and for 3 days after metronidazole therapy prevents the reaction, aligning with standard guidelines. Option B is incorrect as increasing alcohol builds no tolerance and risks severity, while option C is wrong because grapefruit juice does not mitigate flushing. Option D is suboptimal as oral contraceptives are unrelated to this reaction. A clinical pearl is that metronidazole can cause disulfiram-like effects even with small alcohol amounts, lasting up to 4 days post-therapy. In antimicrobial counseling, always screen for alcohol use and advise abstinence, using frameworks like educating on symptom recognition and duration to enhance adherence and safety.

Question 5

1. Continue warfarin and trimethoprim-sulfamethoxazole; advise increasing vitamin K–rich foods to lower the INR
2. Hold warfarin and trimethoprim-sulfamethoxazole, administer oral vitamin K, and arrange prompt INR recheck and bleeding assessment per protocol (correct answer)
3. Stop levothyroxine because it is the most likely cause of the elevated INR and bruising
4. Increase warfarin to 7.5 mg daily because antibiotic therapy can lower INR

Explanation: This question tests management of warfarin-drug interactions causing supratherapeutic INR. The patient's INR of 6.8 with bleeding symptoms after starting trimethoprim-sulfamethoxazole indicates a significant drug interaction, as sulfonamides inhibit warfarin metabolism and displace it from protein binding sites. The correct answer (B) appropriately holds both medications, administers vitamin K for INR reversal, and ensures proper follow-up. Option A is dangerous as continuing both drugs could worsen bleeding, and dietary vitamin K is insufficient for acute management. Option C incorrectly blames levothyroxine which doesn't cause acute INR changes. Option D shows fundamental misunderstanding as antibiotics typically increase, not decrease, warfarin effect. When starting interacting antibiotics in warfarin patients, proactively reduce warfarin dose by 10-25% and monitor INR within 3-5 days to prevent bleeding complications.

Question 6

1. Atorvastatin 20 mg by mouth nightly
2. Metformin 1000 mg by mouth twice daily
3. Lisinopril 20 mg by mouth daily (correct answer)
4. New-onset gastroesophageal reflux disease unrelated to medications

Explanation: This question tests recognition of ACE inhibitor-induced cough, a classic adverse effect. The temporal relationship of dry cough starting 3 weeks after lisinopril initiation clearly identifies it as the causative agent, occurring in 5-10% of patients due to bradykinin accumulation. The correct answer (C) identifies lisinopril as the cause. Option A (atorvastatin) rarely causes cough and the timing doesn't match. Option B (metformin) doesn't cause cough as an adverse effect. Option D suggesting GERD is incorrect as the presentation is classic for ACE inhibitor cough without reflux symptoms. ACE inhibitor cough is dry, persistent, and typically develops within 1-8 weeks of initiation; it resolves within 1-4 weeks of discontinuation. Patients requiring ACE inhibitor therapy who develop cough should be switched to an ARB, which doesn't affect bradykinin metabolism.

Question 7

1. Serum potassium and renal function (serum creatinine) with reassessment of digoxin concentration after dose adjustment (correct answer)
2. Hemoglobin A1c every 3 months to prevent digoxin toxicity
3. International normalized ratio (INR) weekly because digoxin increases warfarin effect
4. Creatine kinase weekly to monitor for digoxin-induced myopathy

Explanation: This question tests monitoring parameters for digoxin toxicity prevention. The patient presents with classic digoxin toxicity symptoms (nausea, anorexia, visual disturbances) with elevated level, worsening renal function, and hypokalemia - all factors that increase digoxin toxicity risk. The correct answer (A) identifies the need to monitor potassium (as hypokalemia increases digoxin binding to Na-K-ATPase) and renal function (as digoxin is renally eliminated). Option B incorrectly suggests HbA1c monitoring which is unrelated to digoxin toxicity. Option C suggests INR monitoring but digoxin doesn't significantly interact with warfarin. Option D incorrectly suggests CK monitoring as digoxin doesn't cause myopathy. Key principle: digoxin has a narrow therapeutic index requiring monitoring of levels, renal function, and potassium, with dose adjustments for declining kidney function and correction of hypokalemia to prevent toxicity.

Question 8

1. Stop gabapentin because it is the most common cause of severe constipation in this regimen
2. Initiate a scheduled stimulant laxative plus stool softener (e.g., senna with docusate) and counsel on hydration/fiber; consider adding an osmotic agent if inadequate response (correct answer)
3. Switch omeprazole to famotidine because proton pump inhibitors cause opioid-related constipation
4. Recommend loperamide 4 mg now then 2 mg after each loose stool to normalize bowel function

Explanation: This question tests management of opioid-induced constipation (OIC), a predictable adverse effect. The patient's constipation after 3 months of regular oxycodone use is classic OIC, occurring in up to 95% of chronic opioid users due to mu-receptor activation in the GI tract. The correct answer (B) appropriately recommends scheduled bowel regimen with stimulant laxative (for motility) plus stool softener, with potential osmotic agent escalation. Option A incorrectly blames gabapentin which rarely causes severe constipation. Option C wrongly implicates omeprazole and misunderstands the mechanism. Option D dangerously recommends loperamide (an anti-diarrheal) which would worsen constipation. Key principle: OIC requires prophylactic bowel regimens starting with opioid initiation, as tolerance doesn't develop to GI effects unlike analgesia, using scheduled rather than PRN laxatives.

Question 9

1. Continue warfarin 5 mg daily because the INR increase is expected and will self-correct
2. Hold 1–2 warfarin doses and reduce the maintenance dose with close INR follow-up due to the amiodarone interaction (correct answer)
3. Stop amiodarone immediately and start clopidogrel 75 mg daily as a substitute for anticoagulation
4. Administer vitamin K 10 mg intravenously routinely for any INR above 5, regardless of bleeding severity

Explanation: This question tests the management of warfarin drug interactions, specifically with amiodarone causing supratherapeutic INR. The key patient-specific factor is the recent initiation of amiodarone, which inhibits warfarin metabolism via CYP2C9, leading to elevated INR (5.6) and minor bleeding in a stable patient. Option B is the best choice because holding 1-2 warfarin doses and reducing the maintenance dose with close INR monitoring safely addresses the interaction without overcorrecting. Option A is incorrect as the INR will not self-correct without adjustment, risking thrombosis or bleeding, and option C is wrong because stopping amiodarone abruptly could destabilize arrhythmia control, and clopidogrel is not a warfarin substitute. Option D is suboptimal as vitamin K is reserved for major bleeding or very high INRs, not routine use. A clinical pearl is that amiodarone can increase warfarin effects by 25-50%, often requiring dose reductions of 20-40%. A decision framework for warfarin interactions involves anticipating potency (e.g., amiodarone's delayed onset), holding doses if INR >4-5 without bleeding, and frequent monitoring post-change.

Question 10

1. Hypoglycemia due to an interaction increasing sulfonylurea effect (correct answer)
2. Hyperglycemia due to trimethoprim-sulfamethoxazole
3. Lactic acidosis due to metformin with normal renal function
4. Diabetic ketoacidosis due to glyburide

Explanation: This question tests the recognition of drug-induced hypoglycemia from sulfonylurea interactions. The key patient-specific factor is the recent initiation of trimethoprim-sulfamethoxazole (TMP-SMX), which inhibits CYP2C9 metabolism of glyburide, leading to enhanced sulfonylurea effects and symptomatic hypoglycemia (glucose 48 mg/dL). Option A is the best choice because it correctly identifies the interaction causing hypoglycemia, requiring TMP-SMX discontinuation or glyburide adjustment. Option B is incorrect as TMP-SMX does not cause hyperglycemia, and option C is wrong because metformin lactic acidosis is rare with normal renal function. Option D is suboptimal as glyburide does not cause diabetic ketoacidosis. A clinical pearl is that sulfonylureas like glyburide have higher hypoglycemia risk in the elderly or with CYP inhibitors like TMP-SMX. A decision framework for hypoglycemia involves checking for drug interactions, treating acutely with glucose, and adjusting therapy to prevent recurrence.

Question 11

1. Indirect hyperbilirubinemia due to atazanavir (benign jaundice with normal transaminases) (correct answer)
2. Acute liver failure due to emtricitabine requiring immediate transplant referral
3. Hemolytic anemia due to ritonavir causing elevated bilirubin with normal liver function tests
4. Cholestatic hepatitis due to tenofovir disoproxil fumarate as the most common toxicity

Explanation: This question tests the recognition of atazanavir-induced indirect hyperbilirubinemia as a benign adverse effect. The key patient-specific factor is the onset of scleral icterus and dark urine 1 month after starting atazanavir, with isolated elevated total bilirubin (4.2 mg/dL) but normal transaminases, due to UGT1A1 inhibition. Option A is the best choice because it identifies the benign, unconjugated hyperbilirubinemia from atazanavir, which does not require discontinuation unless symptomatic. Option B is incorrect as emtricitabine rarely causes liver failure, option C is wrong because ritonavir does not cause hemolytic anemia, and option D is suboptimal as tenofovir causes renal rather than hepatic toxicity. A clinical pearl is that atazanavir commonly causes asymptomatic jaundice in 5-10% of patients, resolving upon discontinuation but often tolerable. In antiretroviral management, monitor bilirubin at baseline and periodically, distinguishing benign elevations from hepatotoxicity by checking direct bilirubin and liver enzymes.

Question 12

1. Advise the patient to continue colchicine hourly until pain resolves and add loperamide for diarrhea
2. Recommend holding further colchicine doses and urgent evaluation for colchicine toxicity, especially given severe renal impairment (correct answer)
3. Switch to probenecid 500 mg by mouth twice daily immediately because it is safer in chronic kidney disease
4. Double the allopurinol dose to 600 mg daily to rapidly treat the acute flare

Explanation: This question tests the management of colchicine overdose and toxicity, particularly in patients with renal impairment. The key patient-specific factor is the patient's excessive colchicine dosing (0.6 mg hourly for 10 hours) in chronic kidney disease stage 4 (creatinine 2.8 mg/dL), leading to gastrointestinal toxicity like severe nausea and vomiting. Option B is the best choice because it recommends holding colchicine and urgent evaluation for toxicity, as renal impairment reduces colchicine clearance and increases risk of life-threatening complications. Option A is incorrect as continuing colchicine would worsen toxicity, and option C is suboptimal because probenecid is not indicated for acute flares and has its own renal risks. Option D is wrong as doubling allopurinol could precipitate more flares without addressing colchicine overdose. A clinical pearl is that colchicine has a narrow therapeutic index, with toxicity (GI, neuromuscular) heightened in renal failure, often requiring supportive care without a specific antidote. In gout management, educate on proper colchicine dosing (e.g., max 1.8 mg/day for flares) and adjust for renal function using frameworks like FDA guidelines.

Question 13

1. Continue TMP-SMX and counsel the patient to increase dietary potassium intake to prevent muscle cramps
2. Hold lisinopril only and continue TMP-SMX; recheck potassium in 2 weeks
3. Recommend immediate evaluation for hyperkalemia, stop TMP-SMX, and notify the prescriber to use an alternative antibiotic (correct answer)
4. Switch spironolactone to eplerenone and continue TMP-SMX because eplerenone does not increase potassium

Explanation: This question tests the recognition and management of drug-induced hyperkalemia from trimethoprim-sulfamethoxazole (TMP-SMX) in patients on renin-angiotensin-aldosterone system (RAAS) inhibitors. The key patient-specific factor is the concurrent use of lisinopril (an ACE inhibitor) and spironolactone (a potassium-sparing diuretic), both of which elevate potassium levels, compounded by the recent initiation of TMP-SMX, leading to symptomatic hyperkalemia (potassium 6.1 mEq/L) with dizziness and near-syncope. Option C is the best choice because it prioritizes immediate evaluation for hyperkalemia, discontinues the offending TMP-SMX, and recommends an alternative antibiotic to treat the cellulitis while mitigating risk, especially given the penicillin allergy limiting options. Option A is incorrect as increasing dietary potassium would worsen hyperkalemia, and option B is suboptimal because holding lisinopril alone fails to address TMP-SMX as the precipitating factor. Option D is wrong because eplerenone also increases potassium levels similarly to spironolactone and does not resolve the TMP-SMX interaction. A key clinical pearl is that TMP-SMX inhibits renal potassium excretion, mimicking hyperkalemia risks seen with amiloride, particularly in patients on RAAS inhibitors or with renal impairment. When managing hyperkalemia, always identify and remove reversible drug causes first, then replete if needed, and monitor closely in high-risk patients like those with heart failure.

Question 14

1. Take tamsulosin at bedtime and rise slowly from sitting/lying positions to reduce orthostatic hypotension risk (correct answer)
2. Take tamsulosin with grapefruit juice to prevent dizziness
3. Double the tamsulosin dose after the first dose to reduce fainting episodes
4. Stop lisinopril permanently because it is incompatible with tamsulosin

Explanation: This question assesses knowledge of managing first-dose hypotension associated with alpha-1 blockers like tamsulosin in patients with benign prostatic hyperplasia. The key patient-specific factor is the timing of the first tamsulosin dose in the morning, combined with concurrent lisinopril use, leading to orthostatic hypotension as evidenced by the standing blood pressure drop and symptoms of dizziness and fainting. Advising to take tamsulosin at bedtime and rise slowly is the best counseling point because it minimizes the risk of orthostatic hypotension by aligning peak effects with sleep and promoting caution during postural changes. Taking with grapefruit juice is incorrect as it does not prevent dizziness and may unpredictably affect drug metabolism without benefit here; doubling the dose is suboptimal and dangerous as it could exacerbate hypotension rather than reduce fainting. Stopping lisinopril permanently is not warranted since the drugs are compatible with monitoring, though dose adjustments might be needed. A transferable clinical pearl is to always counsel on first-dose effects of alpha-blockers, especially in patients on antihypertensives, emphasizing bedtime administration to enhance safety. In practice, use a decision framework that evaluates vital signs, concurrent medications, and patient education to prevent adverse events like syncope.

Question 15

1. Serum potassium and renal function, with dose adjustment/holding digoxin as indicated (correct answer)
2. Hemoglobin A1c, with dose adjustment of digoxin based on glycemic control
3. Alanine aminotransferase and aspartate aminotransferase, with dose adjustment of digoxin based on liver enzymes
4. International normalized ratio, with dose adjustment of digoxin based on anticoagulation intensity

Explanation: This question tests the monitoring and prevention of digoxin toxicity, focusing on electrolyte and renal influences on digoxin levels. The key patient-specific factor is the patient's hypokalemia (3.1 mEq/L) and elevated serum creatinine (1.8 mg/dL) in chronic kidney disease, exacerbating digoxin toxicity symptoms like nausea, anorexia, and visual halos, with a supratherapeutic level (2.6 ng/mL). Option A is the best choice because assessing serum potassium and renal function allows for appropriate digoxin dose adjustment or holding to prevent arrhythmias and further toxicity. Option B is incorrect as hemoglobin A1c is unrelated to digoxin toxicity, and option C is suboptimal because liver enzymes do not directly guide digoxin dosing. Option D is wrong as INR pertains to warfarin, not digoxin management. A clinical pearl is that hypokalemia potentiates digoxin toxicity by increasing cardiac binding, so repletion is crucial in symptomatic patients. A decision framework for digoxin toxicity involves checking levels, electrolytes, and renal function, then holding doses and considering digoxin immune fab for severe cases.

Question 16

1. Metformin 1000 mg by mouth twice daily causing fluid retention
2. Pioglitazone 30 mg by mouth daily worsening edema/heart failure (correct answer)
3. Lisinopril 20 mg by mouth daily causing peripheral edema as the primary adverse effect
4. Furosemide 40 mg by mouth daily causing new-onset fluid overload

Explanation: This question tests the recognition of thiazolidinedione-induced fluid retention exacerbating heart failure. The key patient-specific factor is the onset of ankle swelling and shortness of breath 3 weeks after starting pioglitazone in a patient with heart failure history. Option B is the best choice because pioglitazone causes edema and fluid overload by increasing vascular permeability and sodium retention, worsening heart failure symptoms. Option A is incorrect as metformin does not cause fluid retention, option C is wrong because lisinopril's primary side effect is not edema, and option D is suboptimal as furosemide treats rather than causes fluid overload. A clinical pearl is that thiazolidinediones like pioglitazone are contraindicated in NYHA class III/IV heart failure due to edema risk. In diabetes management for heart failure patients, prefer agents like SGLT2 inhibitors that offer cardioprotective benefits without fluid retention risks.

Question 17

1. Theophylline toxicity due to ciprofloxacin increasing theophylline concentrations (correct answer)
2. Opioid overdose due to ciprofloxacin
3. Serotonin syndrome due to levetiracetam
4. Acute adrenal crisis due to ciprofloxacin

Explanation: This question tests the recognition of theophylline toxicity from CYP1A2 inhibition by ciprofloxacin. The key patient-specific factor is the onset of confusion and unsteady gait after starting ciprofloxacin in a patient on theophylline, with elevated theophylline level (24 mcg/mL) due to reduced clearance in chronic kidney disease. Option A is the best choice because it correctly identifies the interaction causing toxicity, requiring ciprofloxacin discontinuation or theophylline adjustment. Option B is incorrect as ciprofloxacin does not cause opioid overdose, option C is wrong because levetiracetam does not induce serotonin syndrome, and option D is suboptimal as ciprofloxacin does not trigger adrenal crisis. A clinical pearl is that fluoroquinolones like ciprofloxacin can increase theophylline levels by 25-100%, risking seizures or arrhythmias in vulnerable patients. A decision framework for theophylline management involves monitoring levels (target 8-15 mcg/mL for COPD), adjusting for inhibitors, and considering alternatives like inhaled therapies in high-risk cases.

Question 18

1. Continue amoxicillin-clavulanate and add diphenhydramine as needed because this is a common, non-allergic rash
2. Stop amoxicillin-clavulanate immediately, treat as an acute allergic reaction (including appropriate antihistamine and escalation if symptoms worsen), and document a penicillin allergy with prescriber notification for alternative therapy (correct answer)
3. Stop sertraline because selective serotonin reuptake inhibitors commonly cause urticaria within 30 minutes of the first dose
4. Switch the oral contraceptive to a progestin-only product to prevent recurrence of urticaria

Explanation: This question tests recognition and management of acute penicillin allergy. The patient's facial swelling, lip tingling, and urticaria within 30 minutes of first amoxicillin-clavulanate dose indicates IgE-mediated (Type I) hypersensitivity reaction with potential for anaphylaxis progression. The correct answer (B) appropriately stops the offending drug immediately, treats the allergic reaction, documents the allergy, and ensures alternative therapy. Option A is dangerous as continuing the antibiotic could lead to anaphylaxis. Option C incorrectly blames sertraline which doesn't cause acute urticaria. Option D inappropriately focuses on the oral contraceptive which isn't implicated. Penicillin allergies must be taken seriously with immediate discontinuation, appropriate treatment based on severity, and clear documentation to prevent future exposures. Cross-reactivity with cephalosporins is approximately 1-2% with current generation agents.

Question 19

1. Orthostatic hypotension due to additive blood pressure–lowering effects of tamsulosin and sildenafil (correct answer)
2. Hyperkalemia due to the interaction between sildenafil and lisinopril
3. Serotonin syndrome due to sildenafil use
4. Acute bronchospasm due to tamsulosin allergy

Explanation: This question tests recognition of drug interaction-induced orthostatic hypotension. The patient's hypotension and near-syncope after combining tamsulosin (alpha-1 blocker) with sildenafil (PDE5 inhibitor) demonstrates additive vasodilation, as both cause peripheral vasodilation through different mechanisms. The correct answer (A) identifies this pharmacodynamic interaction. Option B incorrectly suggests hyperkalemia which doesn't cause these symptoms and isn't caused by this combination. Option C wrongly invokes serotonin syndrome which sildenafil doesn't cause. Option D incorrectly suggests bronchospasm from tamsulosin allergy which would present with respiratory symptoms. Alpha blockers and PDE5 inhibitors should be used cautiously together with dose separation (4-6 hours), starting with lowest doses, and counseling about orthostatic precautions. Consider alternative BPH treatments like 5-alpha reductase inhibitors in patients requiring PDE5 inhibitors.

Question 20

1. Serotonin syndrome due to linezolid with sertraline (correct answer)
2. Neuroleptic malignant syndrome due to ondansetron
3. Acute dystonia due to sertraline
4. Stevens-Johnson syndrome due to linezolid

Explanation: This question tests the identification of serotonin syndrome from monoamine oxidase inhibitor (MAOI) interactions with serotonergic agents. The key patient-specific factor is the recent initiation of linezolid (a weak MAOI) in a patient on sertraline (an SSRI), leading to symptoms like restlessness, sweating, tremor, diarrhea, fever (38.6°C), and tachycardia (112 bpm). Option A is the best choice because it accurately diagnoses serotonin syndrome due to the linezolid-sertraline interaction, which requires discontinuation of offending agents and supportive care. Option B is incorrect as neuroleptic malignant syndrome is associated with antipsychotics, not ondansetron, and option C is wrong because acute dystonia is not typical of sertraline. Option D is suboptimal as Stevens-Johnson syndrome presents with skin lesions, not these autonomic symptoms. A clinical pearl is that linezolid's MAOI activity can precipitate serotonin syndrome with SSRIs, necessitating a washout period. A decision framework for suspected serotonin syndrome involves assessing the Hunter criteria (e.g., clonus, tremor) and promptly removing serotonergic drugs while providing benzodiazepines for symptom control.