Direct acting sympathomimetics – Methyldopa MCQs With Answer

Direct acting sympathomimetics – Methyldopa MCQs With Answer

Introduction: Methyldopa is a well‑studied antihypertensive frequently covered in B. Pharm pharmacology. Although often categorized among centrally acting agents, its active metabolite acts on alpha‑2 adrenergic receptors to reduce sympathetic outflow. This topic links pharmacokinetics, biotransformation, receptor pharmacology, therapeutic uses (including pregnancy), adverse effects like hepatotoxicity and Coombs‑positive hemolytic anemia, and key drug interactions. These MCQs focus on mechanism, metabolism, clinical applications, monitoring and safety considerations so B. Pharm students can master both conceptual and applied aspects. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the primary mechanism by which methyldopa lowers blood pressure?

• Direct beta‑1 receptor blockade on the heart
• Peripheral alpha‑1 receptor blockade on blood vessels
• Central alpha‑2 adrenergic receptor agonism via an active metabolite
• Inhibition of angiotensin converting enzyme (ACE)

Correct Answer: Central alpha‑2 adrenergic receptor agonism via an active metabolite

Q2. Methyldopa is often described as a “false neurotransmitter.” What does this term mean in its context?

• It directly blocks norepinephrine receptors in the heart
• It is converted to a compound that is stored and released instead of norepinephrine
• It enhances norepinephrine synthesis leading to overstimulation
• It degrades norepinephrine in the synaptic cleft

Correct Answer: It is converted to a compound that is stored and released instead of norepinephrine

Q3. Which enzyme converts methyldopa into alpha‑methyldopamine during its metabolism?

• Monoamine oxidase (MAO)
• Aromatic L‑amino acid decarboxylase (DOPA decarboxylase)
• Dopamine β‑hydroxylase
• Tyrosine hydroxylase

Correct Answer: Aromatic L‑amino acid decarboxylase (DOPA decarboxylase)

Q4. After formation of alpha‑methyldopamine, which enzyme converts it to the active alpha‑methylnorepinephrine?

• Dopamine β‑hydroxylase
• Monoamine oxidase
• Phenylethanolamine N‑methyltransferase
• COMT (catechol‑O‑methyltransferase)

Correct Answer: Dopamine β‑hydroxylase

Q5. Which of the following clinical uses is methyldopa especially known for?

• First‑line therapy for acute myocardial infarction
• Preferred chronic antihypertensive in pregnancy
• Immediate relief of hypertensive emergency in the ICU
• Long‑term management of pheochromocytoma without surgery

Correct Answer: Preferred chronic antihypertensive in pregnancy

Q6. Which adverse effect is classically associated with methyldopa and requires hematologic monitoring?

• Aplastic anemia without hemolysis
• Coombs‑positive hemolytic anemia
• Thrombocytopenia with bleeding
• Leukocytosis due to bone marrow stimulation

Correct Answer: Coombs‑positive hemolytic anemia

Q7. Which laboratory tests are most important to monitor during long‑term methyldopa therapy?

• Renal function and serum potassium only
• Serum glucose and lipid profile
• Liver function tests and direct Coombs test/CBC
• Thyroid function tests and calcium levels

Correct Answer: Liver function tests and direct Coombs test/CBC

Q8. What is a key contraindication or situation of caution for methyldopa use?

• Patients with chronic liver disease due to hepatotoxicity risk
• Patients with hypothyroidism because it increases thyroid hormone
• Use in pregnancy due to teratogenicity
• Use in acute heart failure because it is a strong vasoconstrictor

Correct Answer: Patients with chronic liver disease due to hepatotoxicity risk

Q9. Which of the following best describes methyldopa’s effect on heart rate?

• Produces reflex tachycardia due to peripheral vasodilation
• Causes mild bradycardia through decreased sympathetic tone
• No change in heart rate because it only affects kidneys
• Causes sustained severe bradyarrhythmias in all patients

Correct Answer: Causes mild bradycardia through decreased sympathetic tone

Q10. Abrupt discontinuation of methyldopa can lead to which clinical problem?

• Persistent hypotension unresponsive to fluids
• Rebound hypertension due to sudden return of sympathetic tone
• Hyperkalemia from renal retention
• Acute myocardial necrosis

Correct Answer: Rebound hypertension due to sudden return of sympathetic tone

Q11. Which drug class may reduce the antihypertensive effect of methyldopa by antagonizing central alpha‑2 effects?

• Selective serotonin reuptake inhibitors (SSRIs)
• Tricyclic antidepressants (TCAs)
• Calcium channel blockers
• Thiazide diuretics

Correct Answer: Tricyclic antidepressants (TCAs)

Q12. Which side effect profile is commonly seen with methyldopa due to central sympatholytic action?

• Insomnia and anxiety
• Excessive sedation, fatigue, and dry mouth
• Severe diuresis and hypovolemia
• Increased appetite and weight gain exclusively

Correct Answer: Excessive sedation, fatigue, and dry mouth

Q13. Methyldopa is considered safe in pregnancy primarily because:

• It cannot cross the placenta
• It has an extensive teratogenicity database showing risk is low
• It has a long half‑life ensuring steady fetal levels
• It increases uterine blood flow directly

Correct Answer: It has an extensive teratogenicity database showing risk is low

Q14. Which formulation(s) of methyldopa are commonly available for clinical use?

• Only topical cream
• Oral tablets and injectable (IV/IM) forms
• Inhalation aerosol only
• Transdermal patch exclusively

Correct Answer: Oral tablets and injectable (IV/IM) forms

Q15. Regarding onset of antihypertensive action after oral dosing, methyldopa typically begins to lower blood pressure in:

• Within 5–10 minutes
• Approximately 2–4 hours
• After 48 hours of therapy
• Only after 2 weeks of continuous use

Correct Answer: Approximately 2–4 hours

Q16. Which hemodynamic change is expected with methyldopa therapy?

• Increased total peripheral resistance
• Decreased sympathetic vascular tone leading to reduced TPR
• Marked increase in cardiac output due to reflex mechanisms
• Selective coronary vasoconstriction

Correct Answer: Decreased sympathetic vascular tone leading to reduced TPR

Q17. Methyldopa lowers blood pressure partly by reducing which of the following hormonal responses?

• Aldosterone secretion via adrenal medulla stimulation
• Renin release from the kidney due to reduced sympathetic drive
• Insulin release from pancreatic beta cells
• Thyroid stimulating hormone (TSH) secretion

Correct Answer: Renin release from the kidney due to reduced sympathetic drive

Q18. The active metabolite responsible for methyldopa’s central action is:

• Alpha‑methylnorepinephrine
• Alpha‑methylserotonin
• Beta‑methyldopamine
• Methyldopamine sulfate

Correct Answer: Alpha‑methylnorepinephrine

Q19. Which adverse effect specifically implicates an autoimmune mechanism with methyldopa?

• Direct hepatocellular necrosis only
• Drug‑induced lupus erythematosus exclusively
• Coombs‑positive hemolytic anemia due to autoantibody formation
• IgE‑mediated anaphylactic reactions in most users

Correct Answer: Coombs‑positive hemolytic anemia due to autoantibody formation

Q20. In which patient population is methyldopa particularly preferred over ACE inhibitors or ARBs?

• Young adults with stage 1 hypertension and no comorbidities
• Pregnant women with chronic hypertension
• Patients with bilateral renal artery stenosis
• Patients with acute hypertensive emergency requiring rapid BP drop

Correct Answer: Pregnant women with chronic hypertension

Q21. Which of the following best explains why methyldopa may cause sexual dysfunction?

• It directly antagonizes androgen receptors
• It enhances central sympathetic outflow
• It reduces sympathetic tone required for ejaculation and erection
• It increases testosterone metabolism in the liver

Correct Answer: It reduces sympathetic tone required for ejaculation and erection

Q22. Which symptom should prompt immediate discontinuation and evaluation of methyldopa therapy?

• Mild transient headache
• Development of jaundice or significant rise in liver enzymes
• Temporary dry mouth for a day or two
• Minor decrease in appetite

Correct Answer: Development of jaundice or significant rise in liver enzymes

Q23. Which antihypertensive combination with methyldopa is commonly used to achieve additive blood pressure control?

• Methyldopa plus a beta‑blocker in all patients concurrently
• Methyldopa plus a thiazide diuretic for synergistic effect
• Methyldopa combined with MAO inhibitors routinely
• Methyldopa with high‑dose NSAIDs always

Correct Answer: Methyldopa plus a thiazide diuretic for synergistic effect

Q24. Which monitoring parameter is NOT routinely required for a patient on methyldopa?

• Periodic liver function tests
• Periodic direct Coombs test if anemia suspected
• Routine ECG monitoring in all stable outpatients
• Clinical monitoring for sedation and orthostatic hypotension

Correct Answer: Routine ECG monitoring in all stable outpatients

Q25. Which statement about methyldopa pharmacokinetics is correct?

• It is poorly absorbed orally and must be given IV only
• It is well absorbed orally and metabolized to active compounds in the CNS
• It is eliminated unchanged only by glomerular filtration
• It has negligible penetration into the central nervous system

Correct Answer: It is well absorbed orally and metabolized to active compounds in the CNS

Q26. When comparing methyldopa and clonidine, which is generally true?

• Methyldopa is a direct peripheral alpha‑1 blocker while clonidine is not
• Both reduce central sympathetic outflow, but clonidine is more potent and causes stronger rebound on abrupt withdrawal
• Clonidine acts exclusively peripherally and has no central effects
• Methyldopa is preferred for hypertensive emergencies over clonidine due to rapid onset

Correct Answer: Both reduce central sympathetic outflow, but clonidine is more potent and causes stronger rebound on abrupt withdrawal

Q27. Which of the following is a correct statement on methyldopa and renal function?

• Methyldopa is contraindicated in all patients with any renal impairment
• Methyldopa requires dose adjustment only in severe renal failure due to altered excretion of metabolites
• Methyldopa causes marked hyperkalemia in most patients
• Methyldopa acts by blocking renal angiotensin II receptors

Correct Answer: Methyldopa requires dose adjustment only in severe renal failure due to altered excretion of metabolites

Q28. Which statement best describes methyldopa’s effect on catecholamine stores?

• It increases norepinephrine storage in vesicles exclusively
• It is taken up into adrenergic neurons and forms false neurotransmitters, altering catecholamine stores
• It immediately depletes all catecholamines by inhibiting tyrosine hydroxylase permanently
• It converts norepinephrine into inactive metabolites in the synapse

Correct Answer: It is taken up into adrenergic neurons and forms false neurotransmitters, altering catecholamine stores

Q29. A patient on methyldopa develops fever, anemia and jaundice with a positive direct Coombs test. What is the most likely diagnosis?

• Aplastic anemia
• Coombs‑positive autoimmune hemolytic anemia due to methyldopa
• Hemolytic disease of the newborn transferred to mother
• Iron deficiency anemia unrelated to drug therapy

Correct Answer: Coombs‑positive autoimmune hemolytic anemia due to methyldopa

Q30. In the setting of methyldopa overdose with severe hypotension, the immediate management includes:

• Oral activated charcoal only
• Supportive care with IV fluids and vasopressors as needed
• Administration of high‑dose beta‑blockers to counteract hypotension
• Dialysis as first‑line to remove methyldopa

Correct Answer: Supportive care with IV fluids and vasopressors as needed

Q31. Which adverse effect of methyldopa is most likely due to immune mechanisms rather than direct pharmacologic action?

• Sedation
• Orthostatic hypotension
• Coombs‑positive hemolytic anemia and lupus‑like syndrome
• Dry mouth

Correct Answer: Coombs‑positive hemolytic anemia and lupus‑like syndrome

Q32. Which receptor subtype does alpha‑methylnorepinephrine primarily stimulate to produce antihypertensive effects?

• Beta‑2 adrenergic receptors
• Alpha‑1 adrenergic receptors
• Alpha‑2 adrenergic receptors
• Dopamine D2 receptors

Correct Answer: Alpha‑2 adrenergic receptors

Q33. For chronic control of blood pressure, methyldopa dosing frequency is typically:

• Once daily because of very long half‑life
• Two to three times daily to maintain effect
• Every 6 hours exactly without variation
• Continuous infusion only

Correct Answer: Two to three times daily to maintain effect

Q34. Which adverse CNS effect should pharmacists counsel patients about when dispensing methyldopa?

• Excessive stimulation and insomnia
• Fatigue, drowsiness and depression
• Hallucinations in all patients
• Marked euphoria and hyperactivity

Correct Answer: Fatigue, drowsiness and depression

Q35. Methyldopa’s antihypertensive action is mainly due to:

• Peripheral vasodilation via nitric oxide release
• Reduction in central sympathetic outflow and decreased peripheral resistance
• Direct myocardial depression leading to decreased cardiac output only
• Volume depletion through potent diuresis

Correct Answer: Reduction in central sympathetic outflow and decreased peripheral resistance

Q36. Which medication class would likely produce additive hypotensive effects if given with methyldopa?

• Central stimulants like amphetamines
• Other antihypertensives such as ACE inhibitors or diuretics
• NSAIDs exclusively, always
• Antacids containing magnesium

Correct Answer: Other antihypertensives such as ACE inhibitors or diuretics

Q37. A pregnant patient needs antihypertensive therapy. Which reason supports choosing methyldopa over ACE inhibitors?

• Methyldopa reduces fetal renal function
• ACE inhibitors are teratogenic and contraindicated in pregnancy
• Methyldopa is ineffective for maternal blood pressure control
• ACE inhibitors increase uterine contractions

Correct Answer: ACE inhibitors are teratogenic and contraindicated in pregnancy

Q38. Methyldopa can cause which endocrine-related adverse effect?

• Hyperthyroidism due to TSH stimulation
• Hyperprolactinemia and galactorrhea in some patients
• Severe Cushing’s syndrome in chronic use
• Increased insulin secretion causing hypoglycemia

Correct Answer: Hyperprolactinemia and galactorrhea in some patients

Q39. Which pharmacological property explains why methyldopa can be given orally for chronic therapy?

• It is rapidly destroyed in the GI tract and never absorbed
• It is well absorbed from the gut and converted to active metabolites in vivo
• It requires parenteral administration only due to poor bioavailability
• It is only effective when bound to plasma proteins intravenously

Correct Answer: It is well absorbed from the gut and converted to active metabolites in vivo

Q40. What clinical sign would most likely indicate excessive hypotensive effect from methyldopa?

• Marked hypertension with headache
• Orthostatic dizziness and syncope on standing
• Polyuria and polydipsia
• Rash and urticaria only

Correct Answer: Orthostatic dizziness and syncope on standing

Q41. Which statement about methyldopa and mental health is correct?

• Methyldopa is a stimulant used to treat ADHD
• Methyldopa may worsen depression or cause depressive symptoms in some patients
• Methyldopa cures depression by increasing serotonin centrally
• No psychiatric side effects have ever been reported

Correct Answer: Methyldopa may worsen depression or cause depressive symptoms in some patients

Q42. If a patient on methyldopa develops hemolytic anemia, what is the expected direct Coombs test result?

• Negative direct Coombs test
• Positive direct Coombs test indicating autoimmune hemolysis
• Elevated indirect bilirubin with negative Coombs test only
• Normal hemoglobin and hematocrit always

Correct Answer: Positive direct Coombs test indicating autoimmune hemolysis

Q43. Which statement is true about methyldopa use in hypertensive emergencies?

• Methyldopa is the preferred immediate agent for hypertensive emergency requiring rapid BP control
• Methyldopa is not ideal for urgent BP lowering because its onset is relatively slow compared to IV vasodilators
• Methyldopa causes immediate rebound hypertension if given IV
• Methyldopa must always be combined with nitrates for emergencies

Correct Answer: Methyldopa is not ideal for urgent BP lowering because its onset is relatively slow compared to IV vasodilators

Q44. Which monitoring advice should a pharmacist give to a patient starting methyldopa?

• Avoid reporting any drowsiness; it is unrelated to the drug
• Expect possible drowsiness, report jaundice or unusual bruising, and attend periodic lab tests
• Stop the drug immediately if blood pressure falls by 1–2 mmHg
• No follow‑up is needed once BP control is achieved

Correct Answer: Expect possible drowsiness, report jaundice or unusual bruising, and attend periodic lab tests

Q45. Which of the following best characterizes methyldopa’s interaction with MAO inhibitors?

• MAO inhibitors neutralize methyldopa’s effect completely
• MAO inhibitors can unpredictably alter sympatholytic responses and require caution
• MAO inhibitors always increase methyldopa metabolism making it ineffective
• There is no interaction between MAO inhibitors and methyldopa

Correct Answer: MAO inhibitors can unpredictably alter sympatholytic responses and require caution

Q46. Which adverse event is least likely to be caused by methyldopa?

• Dry mouth and sedation
• Coombs‑positive hemolytic anemia
• Hepatotoxicity
• Severe bronchospasm due to beta‑2 blockade

Correct Answer: Severe bronchospasm due to beta‑2 blockade

Q47. Which patient counseling point is most appropriate for a patient starting methyldopa?

• Stop the medication suddenly if you feel better
• Avoid rapid standing to reduce risk of dizziness and monitor for fatigue or jaundice
• You can double the dose if blood pressure is high once
• There is no need for any lab monitoring while on therapy

Correct Answer: Avoid rapid standing to reduce risk of dizziness and monitor for fatigue or jaundice

Q48. Methyldopa’s long‑term adverse effect profile includes which potentially reversible condition?

• Permanent renal failure in all users
• Drug‑induced autoimmune hemolysis that may resolve after stopping the drug
• Irreversible blindness within days of starting therapy
• Chronic hypoglycemia requiring lifelong treatment

Correct Answer: Drug‑induced autoimmune hemolysis that may resolve after stopping the drug

Q49. Which pharmacologic property best explains methyldopa’s delayed maximal antihypertensive effect compared with some other agents?

• It acts by immediate direct arterial smooth muscle relaxation
• It requires metabolic conversion to active metabolites in the CNS and neuronal uptake**
• It is not absorbed and acts locally in the gut
• It is rapidly excreted unchanged before effect

Correct Answer: It requires metabolic conversion to active metabolites in the CNS and neuronal uptake**

Q50. Which choice correctly lists two serious but uncommon toxicities of methyldopa that require vigilance?

• Hyperkalemia and urinary retention
• Coombs‑positive hemolytic anemia and hepatotoxicity
• Peripheral neuropathy and pancreatitis
• Acute pulmonary edema and hypothermia

Correct Answer: Coombs‑positive hemolytic anemia and hepatotoxicity

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