Methimazole MCQs With Answer

Methimazole MCQs With Answer

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Methimazole is a key antithyroid drug widely used in the management of hyperthyroidism, particularly Graves’ disease. It inhibits thyroid peroxidase, blocking iodination and coupling steps to reduce T3/T4 synthesis. B. Pharm students should grasp methimazole’s mechanism of action, pharmacokinetics, once-daily dosing, clinical uses (preoperative preparation, long-term control), and important adverse effects such as agranulocytosis, cholestatic hepatitis, and teratogenic risks. Comparative points with propylthiouracil (PTU), monitoring requirements (CBC, LFTs), management of severe reactions, and pregnancy/lactation considerations are essential for exams and practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which enzyme is primarily inhibited by methimazole in the thyroid gland?

  • Thyroid peroxidase (TPO)
  • 5′-deiodinase
  • Thyroglobulin synthetase
  • Sodium-iodide symporter

Correct Answer: Thyroid peroxidase (TPO)

Q2. Methimazole directly blocks which steps of thyroid hormone synthesis?

  • Iodination of tyrosyl residues and coupling of iodotyrosines
  • Peripheral conversion of T4 to T3
  • Release of preformed T3 and T4 from colloid
  • Synthesis of thyroxine-binding globulin

Correct Answer: Iodination of tyrosyl residues and coupling of iodotyrosines

Q3. Which statement about methimazole and peripheral conversion of thyroid hormones is correct?

  • Methimazole significantly inhibits peripheral conversion of T4 to T3
  • Methimazole has minimal effect on peripheral conversion of T4 to T3
  • Methimazole increases peripheral T4 to T3 conversion
  • Methimazole irreversibly blocks deiodinase enzymes

Correct Answer: Methimazole has minimal effect on peripheral conversion of T4 to T3

Q4. When do patients typically begin to show clinical improvement after starting methimazole?

  • Within 24 hours
  • 2–4 weeks
  • 6–12 months
  • After radioactive iodine therapy only

Correct Answer: 2–4 weeks

Q5. What is a common dosing advantage of methimazole compared with propylthiouracil (PTU)?

  • Methimazole is typically given once daily due to longer duration of action
  • Methimazole requires continuous IV infusion
  • Methimazole must be given hourly
  • Methimazole cannot be given orally

Correct Answer: Methimazole is typically given once daily due to longer duration of action

Q6. Which serious hematologic adverse effect is most classically associated with methimazole?

  • Agranulocytosis (severe neutropenia)
  • Macrocytic anemia
  • Polycythemia vera
  • Hemolytic anemia due to G6PD

Correct Answer: Agranulocytosis (severe neutropenia)

Q7. Which baseline and symptom-driven test is most important to detect methimazole-induced agranulocytosis?

  • Complete blood count (CBC) with differential
  • Serum creatinine
  • Thyroid-stimulating immunoglobulin (TSI)
  • Electrolyte panel

Correct Answer: Complete blood count (CBC) with differential

Q8. What is the immediate management when a patient on methimazole develops agranulocytosis?

  • Stop methimazole immediately and provide supportive care, consider G-CSF
  • Continue methimazole and add broad-spectrum antibiotics only
  • Increase the methimazole dose
  • Switch to another antithyroid drug without stopping methimazole

Correct Answer: Stop methimazole immediately and provide supportive care, consider G-CSF

Q9. Which statement about methimazole use in pregnancy is most accurate?

  • Methimazole is associated with teratogenicity in the first trimester; PTU is preferred early in pregnancy
  • Methimazole is completely safe during all trimesters and is the first-line drug
  • Methimazole should always be combined with radioactive iodine in pregnancy
  • Methimazole is contraindicated during breastfeeding only

Correct Answer: Methimazole is associated with teratogenicity in the first trimester; PTU is preferred early in pregnancy

Q10. Which congenital defect has been linked to first-trimester exposure to methimazole?

  • Aplasia cutis (scalp defects)
  • Neural tube defect
  • Cardiac septal defect only
  • Clubfoot exclusively

Correct Answer: Aplasia cutis (scalp defects)

Q11. Regarding severe hepatic injury, how do methimazole and PTU compare?

  • PTU has been more commonly associated with severe hepatic necrosis, while methimazole more often causes cholestatic patterns
  • Methimazole always causes fulminant hepatic failure more than PTU
  • Neither drug affects the liver
  • Both drugs produce identical patterns of liver injury equally

Correct Answer: PTU has been more commonly associated with severe hepatic necrosis, while methimazole more often causes cholestatic patterns

Q12. In the treatment of thyroid storm, why is PTU often preferred over methimazole?

  • PTU also inhibits peripheral conversion of T4 to T3 in addition to blocking synthesis
  • PTU can be given as a depot injection for long-term control
  • Methimazole is ineffective in thyroid storm
  • PTU has no side effects in thyroid storm patients

Correct Answer: PTU also inhibits peripheral conversion of T4 to T3 in addition to blocking synthesis

Q13. Which baseline laboratory tests are recommended before initiating methimazole therapy?

  • Complete blood count (CBC) and liver function tests (LFTs)
  • Serum troponin only
  • Urine culture only
  • Fasting lipid profile only

Correct Answer: Complete blood count (CBC) and liver function tests (LFTs)

Q14. Why is methimazole used to prepare hyperthyroid patients prior to thyroid surgery?

  • To achieve a euthyroid state and reduce the risk of perioperative thyroid storm
  • To permanently destroy the thyroid before surgery
  • To increase blood flow to the thyroid gland
  • To enhance radioactive iodine uptake during surgery

Correct Answer: To achieve a euthyroid state and reduce the risk of perioperative thyroid storm

Q15. What is a pharmacokinetic reason methimazole is often dosed once daily?

  • It has a relatively long duration of action allowing once-daily dosing
  • It is not absorbed orally
  • It is rapidly eliminated requiring continuous infusion
  • It is only active when given with food every 24 hours

Correct Answer: It has a relatively long duration of action allowing once-daily dosing

Q16. Which specific synthetic steps in the thyroid follicle are blocked by methimazole?

  • Oxidation of iodide and iodination/coupling of tyrosyl residues on thyroglobulin
  • Endocytosis of colloid only
  • Synthesis of TSH in the pituitary
  • Conversion of iodine to sodium iodide

Correct Answer: Oxidation of iodide and iodination/coupling of tyrosyl residues on thyroglobulin

Q17. What is the usual route of administration for methimazole in outpatient management?

  • Oral tablets
  • Intramuscular injection only
  • Continuous intravenous infusion
  • Topical application

Correct Answer: Oral tablets

Q18. Regarding lactation, which statement about methimazole is correct?

  • Methimazole is excreted in breast milk but low-to-moderate doses are generally compatible with breastfeeding with monitoring
  • Methimazole is absolutely contraindicated during breastfeeding
  • Methimazole increases milk production and is used to treat mastitis
  • Methimazole is converted to PTU in breast milk

Correct Answer: Methimazole is excreted in breast milk but low-to-moderate doses are generally compatible with breastfeeding with monitoring

Q19. Which of the following is an early non-hematologic adverse effect of methimazole?

  • Maculopapular rash and pruritus
  • Immediate anaphylactic shock in all patients
  • Chronic renal failure within 24 hours
  • Permanent blindness in most patients

Correct Answer: Maculopapular rash and pruritus

Q20. Which action is NOT produced by methimazole?

  • Immediate inhibition of release of preformed T3 and T4 from the thyroid
  • Inhibition of thyroid hormone synthesis via TPO blockade
  • Potential long-term reduction of thyroid autoantibody levels
  • Reduction in new hormone synthesis leading to gradual clinical improvement

Correct Answer: Immediate inhibition of release of preformed T3 and T4 from the thyroid

Q21. In pediatric patients with hyperthyroidism, which antithyroid agent is generally preferred for long-term medical therapy?

  • Methimazole
  • Propylthiouracil (PTU)
  • Radioactive iodine as first-line in all children
  • Levothyroxine instead of antithyroid drugs

Correct Answer: Methimazole

Q22. A patient develops a mild pruritic rash after starting methimazole. What is an appropriate initial approach?

  • Consider antihistamine therapy and continue methimazole if rash is mild and non-progressive
  • Immediately perform thyroidectomy
  • Increase the methimazole dose
  • Switch to radioactive iodine the same day

Correct Answer: Consider antihistamine therapy and continue methimazole if rash is mild and non-progressive

Q23. How do antithyroid drugs like methimazole affect levels of thyroid-stimulating immunoglobulins (TSI) in Graves’ disease over time?

  • They may reduce TSI titers gradually with prolonged therapy
  • They immediately eliminate TSI within hours
  • They invariably increase TSI levels
  • They convert TSI into TSH

Correct Answer: They may reduce TSI titers gradually with prolonged therapy

Q24. In agranulocytosis caused by methimazole, which laboratory abnormality is most characteristic?

  • Marked neutropenia (very low absolute neutrophil count)
  • Hypercalcemia
  • Elevated hemoglobin above normal
  • Increased platelet count

Correct Answer: Marked neutropenia (very low absolute neutrophil count)

Q25. Why is methimazole commonly discontinued before radioactive iodine (RAI) therapy?

  • Antithyroid drugs can reduce radioiodine uptake and blunt RAI efficacy, so stopping them increases RAI effectiveness
  • Methimazole contains radioactive isotopes that interfere with RAI
  • Methimazole converts RAI into inactive metabolites
  • There is no need to stop methimazole before RAI

Correct Answer: Antithyroid drugs can reduce radioiodine uptake and blunt RAI efficacy, so stopping them increases RAI effectiveness

Q26. Which hepatic injury pattern is more typically associated with methimazole?

  • Cholestatic liver injury (cholestatic jaundice)
  • Immediate fulminant hepatic necrosis in all patients
  • Renal-type hepatic injury only
  • No hepatic effects at all

Correct Answer: Cholestatic liver injury (cholestatic jaundice)

Q27. What is the usual therapeutic strategy when initiating methimazole for Graves’ disease?

  • Start with a higher initial dose to control hyperthyroidism, then taper to the lowest effective maintenance dose
  • Begin with a very low dose and never adjust it
  • Give a single bolus dose and stop forever
  • Combine with long-term high-dose corticosteroids as standard

Correct Answer: Start with a higher initial dose to control hyperthyroidism, then taper to the lowest effective maintenance dose

Q28. Methimazole has been associated with which autoimmune complication involving small vessels?

  • ANCA-associated vasculitis
  • Goodpasture’s syndrome exclusively
  • Rheumatoid arthritis in all patients
  • Systemic lupus erythematosus in every case

Correct Answer: ANCA-associated vasculitis

Q29. Which investigations are recommended at baseline before starting methimazole therapy for safe monitoring?

  • Thyroid function tests, CBC, and liver function tests
  • Only chest X-ray
  • Only urinalysis
  • Only pregnancy test without any labs

Correct Answer: Thyroid function tests, CBC, and liver function tests

Q30. If a patient develops life-threatening methimazole toxicity and antithyroid drugs can no longer be used, what are appropriate definitive treatment options for hyperthyroidism?

  • Urgent withdrawal of the drug and consideration of definitive therapy such as radioiodine ablation or thyroidectomy
  • Continue methimazole and add increasing doses indefinitely
  • Only dietary changes without definitive therapy
  • Switch to daily high-dose aspirin therapy

Correct Answer: Urgent withdrawal of the drug and consideration of definitive therapy such as radioiodine ablation or thyroidectomy

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