Thioridazine hydrochloride MCQs With Answer

Thioridazine hydrochloride MCQs With Answer is a focused study resource designed for B.Pharm students to master this phenothiazine antipsychotic’s pharmacology, mechanism of action, dosing, pharmacokinetics, adverse effects and drug interactions. These concise, exam-oriented questions emphasize key concepts such as D2 receptor antagonism, cardiac safety (QT prolongation), metabolic pathways (CYP-mediated), ocular toxicity and clinical monitoring. Ideal for revision and competitive exams, the questions deepen understanding of formulation aspects (hydrochloride salt), therapeutic considerations, contraindications and counselling points. Clear explanations and repeated practice improve retention and clinical reasoning. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which receptor blockade primarily explains the antipsychotic effect of thioridazine?

• Serotonin 5-HT2A receptor agonism
• Histamine H1 receptor antagonism
• Dopamine D2 receptor antagonism
• GABA-A receptor potentiation

Correct Answer: Dopamine D2 receptor antagonism

Q2. Thioridazine hydrochloride belongs to which chemical class of antipsychotics?

• Butyrophenones
• Phenothiazines
• Benzodiazepines
• Tricyclic antidepressants

Correct Answer: Phenothiazines

Q3. The hydrochloride salt form of thioridazine is used primarily to improve which property?

• Receptor selectivity
• Oral bioavailability and aqueous solubility
• Intrinsic pharmacologic potency
• Ability to cross the blood–brain barrier

Correct Answer: Oral bioavailability and aqueous solubility

Q4. Which serious cardiac adverse effect is most classically associated with thioridazine?

• Myocardial infarction
• QT interval prolongation leading to torsades de pointes
• Bradycardia due to SA node destruction
• Hypertrophic cardiomyopathy

Correct Answer: QT interval prolongation leading to torsades de pointes

Q5. Which of the following metabolic enzymes is most involved in thioridazine biotransformation?

• CYP2D6
• CYP1A2
• CYP2E1
• Monoamine oxidase

Correct Answer: CYP2D6

Q6. A major ocular toxicity linked to chronic thioridazine use is:

• Optic neuritis
• Pigmentary retinopathy
• Cataract formation
• Glaucoma

Correct Answer: Pigmentary retinopathy

Q7. Which pharmacodynamic property of thioridazine contributes to sedation and weight gain?

• Alpha-1 adrenergic agonism
• Histamine H1 receptor antagonism
• Dopamine D2 partial agonism
• Glycine receptor activation

Correct Answer: Histamine H1 receptor antagonism

Q8. Which of the following best describes thioridazine’s typical effect on extrapyramidal symptoms (EPS) compared with high-potency typical antipsychotics?

• Higher risk of acute EPS than haloperidol
• Lower incidence of EPS due to stronger anticholinergic activity
• No EPS because it is an atypical antipsychotic
• Immediate irreversible EPS after single dose

Correct Answer: Lower incidence of EPS due to stronger anticholinergic activity

Q9. Co-administration of thioridazine with which drug class increases the risk of severe QT prolongation?

• Selective serotonin reuptake inhibitors with known QT effects (e.g., citalopram)
• Topical antifungals
• Nonsteroidal anti-inflammatory drugs
• H2 receptor antagonists without cardiac effects

Correct Answer: Selective serotonin reuptake inhibitors with known QT effects (e.g., citalopram)

Q10. The common anticholinergic adverse effects of thioridazine include:

• Diarrhea and increased sweating
• Urinary retention, dry mouth, blurred vision
• Hypersalivation and rhinorrhea
• Bronchorrhea and lacrimation

Correct Answer: Urinary retention, dry mouth, blurred vision

Q11. Thioridazine’s active metabolites include:

• Mesoridazine and sulforidazine
• Risperidone and paliperidone
• Haloperidol and droperidol
• Propranolol and metoprolol

Correct Answer: Mesoridazine and sulforidazine

Q12. Which monitoring is most important before and during therapy with thioridazine?

• Liver ultrasound every month
• Baseline and periodic ECG to monitor QT interval
• Daily fasting glucose measurement
• Routine MRI of the brain

Correct Answer: Baseline and periodic ECG to monitor QT interval

Q13. A pharmacist should counsel a patient on thioridazine to avoid which activity due to sedative effects?

• Eating protein-rich foods
• Operating heavy machinery or driving
• Taking multivitamins
• Sun exposure

Correct Answer: Operating heavy machinery or driving

Q14. Thioridazine’s antipsychotic efficacy is primarily for which symptom domain of schizophrenia?

• Negative symptoms only
• Positive symptoms such as hallucinations and delusions
• Cognitive remediation
• Preventing progression of neurodegeneration

Correct Answer: Positive symptoms such as hallucinations and delusions

Q15. Which pharmacokinetic property explains thioridazine’s tendency to accumulate in adipose tissue?

• High water solubility
• High lipophilicity
• Low protein binding
• Rapid renal excretion unchanged

Correct Answer: High lipophilicity

Q16. Thioridazine-induced orthostatic hypotension is mainly due to blockade of which receptor?

• Beta-2 adrenergic receptors
• Alpha-1 adrenergic receptors
• Dopamine D4 receptors
• Muscarinic M2 receptors

Correct Answer: Alpha-1 adrenergic receptors

Q17. Which lab test should be considered in patients on chronic thioridazine therapy presenting with weakness and pallor?

• Thyroid function test
• Complete blood count to assess for leukopenia or anemia
• Serum amylase only
• Serum vitamin D level

Correct Answer: Complete blood count to assess for leukopenia or anemia

Q18. Which of the following interactions can increase plasma thioridazine levels?

• CYP2D6 inhibitors such as fluoxetine or paroxetine
• CYP2D6 inducers such as rifampicin
• Concurrent use of metformin
• Use of oral contraceptives without enzyme effects

Correct Answer: CYP2D6 inhibitors such as fluoxetine or paroxetine

Q19. Tardive dyskinesia associated with thioridazine is best described as:

• An acute reversible muscle spasm in the first day of therapy
• A late-onset potentially irreversible hyperkinetic movement disorder
• Peripheral neuropathy of sensory nerves
• Autonomic neuropathy causing hypotension

Correct Answer: A late-onset potentially irreversible hyperkinetic movement disorder

Q20. Which patient population requires extra caution or avoidance of thioridazine due to increased cardiac risk?

• Young adults aged 18–25 with no cardiac history
• Patients with congenital long QT syndrome
• Patients with controlled hypothyroidism
• Patients on vitamin supplements only

Correct Answer: Patients with congenital long QT syndrome

Q21. The primary route of elimination for thioridazine and its metabolites is:

• Renal excretion of unchanged drug exclusively
• Hepatic metabolism followed by renal and biliary excretion of metabolites
• Exhalation as unchanged drug
• Secretion in sweat as primary route

Correct Answer: Hepatic metabolism followed by renal and biliary excretion of metabolites

Q22. Which adverse effect of thioridazine is least likely due to its anticholinergic activity?

• Constipation
• Dry mouth
• Blurred vision
• Bradykinesia (parkinsonism)

Correct Answer: Bradykinesia (parkinsonism)

Q23. Which statement about thioridazine and pregnancy is most appropriate for counseling?

• It is absolutely safe and requires no monitoring during pregnancy
• Use only if potential benefit justifies potential risk; consider specialist advice
• It enhances fetal growth and is recommended in first trimester
• It prevents gestational diabetes when taken daily

Correct Answer: Use only if potential benefit justifies potential risk; consider specialist advice

Q24. In terms of receptor profile, thioridazine shows which combination contributing to fewer EPS but more anticholinergic effects?

• High D2 blockade with negligible anticholinergic activity
• Moderate D2 blockade plus strong muscarinic receptor antagonism
• Pure serotonin reuptake inhibition
• Strong GABA-A agonism with dopaminergic stimulation

Correct Answer: Moderate D2 blockade plus strong muscarinic receptor antagonism

Q25. Which antibiotic is known to interact dangerously with thioridazine by prolonging QT interval?

• Amoxicillin
• Erythromycin or other macrolides
• Doxycycline without QT effects
• Cephalexin

Correct Answer: Erythromycin or other macrolides

Q26. The onset of action for antipsychotic effects of thioridazine is generally:

• Within minutes after a single dose
• Several days to weeks, with improvement in agitation first
• Complete remission within 24 hours
• Only after months with no early changes

Correct Answer: Several days to weeks, with improvement in agitation first

Q27. Which laboratory abnormality can be monitored for metabolic risk during long-term thioridazine therapy?

• Serum creatine kinase only
• Lipid profile and fasting glucose
• Serum amylase exclusively
• Urine ketones daily

Correct Answer: Lipid profile and fasting glucose

Q28. When counseling on ocular toxicity risk, what advice should be given to patients on thioridazine?

• No eye checks are necessary
• Report visual changes and have periodic ophthalmologic examinations
• Only children need eye exams
• Stop wearing contact lenses permanently

Correct Answer: Report visual changes and have periodic ophthalmologic examinations

Q29. Which formulation consideration is typical for thioridazine hydrochloride tablets?

• They are injectable only
• Oral tablets with improved stability and solubility due to hydrochloride salt
• Gaseous inhalation formulation is standard
• Only transdermal patch available commercially

Correct Answer: Oral tablets with improved stability and solubility due to hydrochloride salt

Q30. A key counselling point regarding sun exposure while taking thioridazine is:

• There is no photosensitivity risk
• Use sun protection because phenothiazines may increase photosensitivity
• Sun exposure increases drug efficacy
• Always sunbathe to reduce sedation

Correct Answer: Use sun protection because phenothiazines may increase photosensitivity

Q31. Which effect is most likely to be improved early in therapy with thioridazine?

• Cognitive deficits of schizophrenia
• Acute agitation and severe psychomotor disturbance
• Negative symptoms such as social withdrawal permanently
• Long-term structural brain changes

Correct Answer: Acute agitation and severe psychomotor disturbance

Q32. Which of the following is a contraindication to starting thioridazine?

• Mild seasonal allergies
• Known history of significant QT prolongation or torsades de pointes
• Well-controlled hypertension on ACE inhibitors
• History of migraine headaches without cardiac disease

Correct Answer: Known history of significant QT prolongation or torsades de pointes

Q33. Which monitoring parameter should be considered when thioridazine is used with other drugs that prolong QT?

• Periodic audiometry
• Frequent ECG monitoring and electrolyte checks (potassium, magnesium)
• Daily complete blood count only
• Bone mineral density scans

Correct Answer: Frequent ECG monitoring and electrolyte checks (potassium, magnesium)

Q34. The risk of neuroleptic malignant syndrome (NMS) with thioridazine is characterized by:

• Gradual onset with only mild fatigue
• Acute hyperthermia, muscle rigidity, altered mental status and autonomic instability
• Painless rash and mild fever only
• Exclusive involvement of peripheral nerves

Correct Answer: Acute hyperthermia, muscle rigidity, altered mental status and autonomic instability

Q35. Which patient advice is appropriate regarding alcohol consumption while taking thioridazine?

• Alcohol has no interaction and is safe in any amount
• Avoid alcohol because it increases CNS depression and sedation
• Drink alcohol to counteract anticholinergic effects
• Alcohol reduces QT risk and is beneficial

Correct Answer: Avoid alcohol because it increases CNS depression and sedation

Q36. The presence of which symptom would suggest extrapyramidal parkinsonism from thioridazine?

• Resting tremor, rigidity, bradykinesia
• Excessive lacrimation only
• Increased appetite and weight loss
• Improved fine motor coordination

Correct Answer: Resting tremor, rigidity, bradykinesia

Q37. In case of suspected thioridazine overdose with arrhythmia, an immediate clinical priority is:

• Administer high-dose benzodiazepines only
• Obtain ECG and manage arrhythmia; correct electrolytes and consider cardiology input
• Give aspirin and clopidogrel
• Advise bed rest and outpatient follow-up

Correct Answer: Obtain ECG and manage arrhythmia; correct electrolytes and consider cardiology input

Q38. Which of the following best explains why elderly patients are at higher risk for adverse effects from thioridazine?

• Enhanced hepatic clearance in elderly
• Altered pharmacokinetics, polypharmacy, increased cardiac and anticholinergic sensitivity
• They metabolize drugs faster than younger adults
• Elderly patients are immune to QT prolongation

Correct Answer: Altered pharmacokinetics, polypharmacy, increased cardiac and anticholinergic sensitivity

Q39. Which symptom would prompt immediate discontinuation of thioridazine and urgent medical evaluation?

• New onset visual disturbances and palpitations
• Mild transient headache after dose
• Temporary mild dry mouth that improves
• Improved sleep quality

Correct Answer: New onset visual disturbances and palpitations

Q40. The therapeutic index of thioridazine is best described as:

• Extremely wide with no toxicity concerns
• Narrow to moderate, requiring careful dosing and monitoring due to cardiac toxicity
• Infinite because it is non-toxic
• Only determined by weight and not relevant clinically

Correct Answer: Narrow to moderate, requiring careful dosing and monitoring due to cardiac toxicity

Q41. Which effect on prolactin levels is typically seen with dopamine D2 antagonists like thioridazine?

• Decreased prolactin levels leading to hypoprolactinemia
• Increased prolactin levels leading to hyperprolactinemia
• No change in prolactin levels
• Prolactin conversion to cortisol

Correct Answer: Increased prolactin levels leading to hyperprolactinemia

Q42. When formulating thioridazine hydrochloride tablets, a pharmaceutical scientist focuses on which excipient goal?

• Reduce water solubility to zero
• Enhance stability, control release and mask taste while maintaining solubility
• Convert it to an injectable oil-only form
• Ensure the tablet disintegrates only after 7 days

Correct Answer: Enhance stability, control release and mask taste while maintaining solubility

Q43. Which counseling point is important regarding missed doses of thioridazine?

• Double the next dose if one dose is missed
• Take the missed dose as soon as remembered unless it is near the time of the next dose
• Stop therapy permanently after one missed dose
• Increase dose gradually over the next week to compensate

Correct Answer: Take the missed dose as soon as remembered unless it is near the time of the next dose

Q44. Combining thioridazine with strong CYP2D6 inhibitors may require which clinical action?

• Increase the thioridazine dose immediately
• Reduce thioridazine dose or avoid combination due to increased plasma levels and QT risk
• No change; combinations are always safe
• Prescribe additional anticholinergic agents by default

Correct Answer: Reduce thioridazine dose or avoid combination due to increased plasma levels and QT risk

Q45. Which adverse endocrine effect can occur with chronic thioridazine therapy?

• Hyperthyroidism only
• Hyperprolactinemia leading to galactorrhea and sexual dysfunction
• Adrenal insufficiency always
• Increased insulin sensitivity universally

Correct Answer: Hyperprolactinemia leading to galactorrhea and sexual dysfunction

Q46. For B.Pharm students studying drug-drug interactions, which example illustrates a pharmacokinetic interaction increasing thioridazine levels?

• Co-administration with activated charcoal improving clearance
• Coadministration with paroxetine (CYP2D6 inhibitor) raising thioridazine concentrations
• Combining with laxatives to enhance renal excretion
• Concurrent use of vitamin C reducing absorption

Correct Answer: Coadministration with paroxetine (CYP2D6 inhibitor) raising thioridazine concentrations

Q47. Which symptom cluster differentiates anticholinergic toxicity from extrapyramidal effects?

• Bradykinesia and rigidity vs. dry mouth and urinary retention
• Dry mouth, blurred vision, urinary retention vs. rigidity, tremor, bradykinesia
• Excessive salivation vs. severe constipation only
• Only changes in taste vs. only insomnia

Correct Answer: Dry mouth, blurred vision, urinary retention vs. rigidity, tremor, bradykinesia

Q48. Which statement about thioridazine and CYP enzyme induction is correct?

• Rifampicin coadministration may decrease thioridazine levels via CYP induction
• CYP inducers universally increase thioridazine plasma levels
• CYP enzymes have no effect on thioridazine metabolism
• CYP induction always causes QT prolongation

Correct Answer: Rifampicin coadministration may decrease thioridazine levels via CYP induction

Q49. In formulary decisions, why might a clinician prefer an antipsychotic other than thioridazine today?

• Because thioridazine has no antipsychotic efficacy
• Due to safer cardiac profile and lower risk of severe QT prolongation with many alternatives
• Because thioridazine is the only injectable option
• Because thioridazine is preferred in pregnancy universally

Correct Answer: Due to safer cardiac profile and lower risk of severe QT prolongation with many alternatives

Q50. Which educational point is essential when teaching B.Pharm students about thioridazine pharmacology?

• Only memorizing brand names is sufficient for clinical use
• Understand receptor profile, metabolism (CYP interactions), cardiac risks, and counselling to ensure safe use
• Pharmacodynamics are irrelevant for dispensing
• Always recommend over-the-counter use without monitoring

Correct Answer: Understand receptor profile, metabolism (CYP interactions), cardiac risks, and counselling to ensure safe use

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com