Biguanides – Metformin MCQs With Answer

Biguanides – Metformin MCQs With Answer

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Biguanides, primarily metformin, are cornerstone oral antihyperglycemic agents in diabetes pharmacotherapy. This concise guide for B.Pharm students explains metformin’s pharmacodynamics (AMPK activation, mitochondrial complex I inhibition), pharmacokinetics (oral bioavailability, renal excretion, minimal metabolism), clinical uses (type 2 diabetes, PCOS, NAFLD), dosing and formulation differences (IR vs ER), adverse effects (gastrointestinal intolerance, vitamin B12 deficiency, rare lactic acidosis), contraindications (severe renal/hepatic impairment, hypoxia) and key drug interactions (cimetidine, iodinated contrast). Focus on monitoring parameters (eGFR, B12) and mechanisms will strengthen safe, evidence-based use. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which of the following drugs is the prototype biguanide used as first-line therapy in type 2 diabetes?

  • Glibenclamide
  • Pioglitazone
  • Metformin
  • Acarbose

Correct Answer: Metformin

Q2. What is the primary cellular mechanism by which metformin decreases hepatic glucose production?

  • Direct stimulation of pancreatic beta cells
  • Activation of AMP-activated protein kinase (AMPK)
  • Inhibition of intestinal carbohydrate digestion
  • Direct agonism at insulin receptors

Correct Answer: Activation of AMP-activated protein kinase (AMPK)

Q3. Metformin lowers blood glucose majorly by:

  • Increasing renal glucose reabsorption
  • Enhancing hepatic gluconeogenesis
  • Decreasing hepatic gluconeogenesis
  • Stimulating glucagon secretion

Correct Answer: Decreasing hepatic gluconeogenesis

Q4. What is the approximate oral bioavailability of immediate-release metformin in humans?

  • 5–10%
  • 20–30%
  • 50–60%
  • 90–100%

Correct Answer: 50–60%

Q5. How is metformin primarily eliminated from the body?

  • Hepatic metabolism via CYP450 enzymes
  • Renal excretion unchanged
  • Metabolism to active metabolites excreted in feces
  • Biliary excretion after glucuronidation

Correct Answer: Renal excretion unchanged

Q6. Which transporters are most important for metformin uptake and renal secretion?

  • P-glycoprotein and OATP1B1
  • OCT2 and MATE transporters
  • GLUT4 and SGLT2
  • CYP3A4 and CYP2D6

Correct Answer: OCT2 and MATE transporters

Q7. What is the typical plasma elimination half-life of metformin after oral dosing?

  • 30 minutes
  • 4–8 hours
  • 24–48 hours
  • 7–14 days

Correct Answer: 4–8 hours

Q8. Metformin is contraindicated in patients with which of the following renal conditions?

  • eGFR 75 mL/min/1.73 m2
  • eGFR 45 mL/min/1.73 m2
  • eGFR <30 mL/min/1.73 m2
  • eGFR 60–90 mL/min/1.73 m2

Correct Answer: eGFR <30 mL/min/1.73 m2

Q9. Before administration of iodinated contrast media, what is recommended regarding metformin?

  • Continue metformin without interruption
  • Double the dose on the day of contrast
  • Temporarily discontinue metformin and assess renal function
  • Switch to insulin for one year

Correct Answer: Temporarily discontinue metformin and assess renal function

Q10. The most common adverse effects of metformin are:

  • Hypoglycemia and weight gain
  • Gastrointestinal symptoms (nausea, diarrhea)
  • Severe hepatic necrosis
  • Dry mouth and tachycardia

Correct Answer: Gastrointestinal symptoms (nausea, diarrhea)

Q11. Long-term metformin therapy is associated with a deficiency in which vitamin?

  • Vitamin D
  • Vitamin B12
  • Vitamin K
  • Vitamin C

Correct Answer: Vitamin B12

Q12. Lactic acidosis associated with metformin is:

  • Common and mild in most patients
  • Nonexistent; metformin cannot cause lactic acidosis
  • Rare but serious, risk increased with renal/hepatic impairment and hypoxia
  • Prevented by taking metformin with food only

Correct Answer: Rare but serious, risk increased with renal/hepatic impairment and hypoxia

Q13. A commonly used initial dose of immediate-release metformin in adults is:

  • 500 mg twice daily
  • 10 mg once daily
  • 2 g as a single morning dose
  • 50 mg intramuscularly

Correct Answer: 500 mg twice daily

Q14. The usual maximum recommended daily dose of metformin (IR/ER) for glycemic control is approximately:

  • 500 mg/day
  • 1000 mg/day
  • 2000 mg/day
  • 10,000 mg/day

Correct Answer: 2000 mg/day

Q15. Compared with many other oral antidiabetic drugs, metformin’s effect on body weight is best described as:

  • Marked weight gain
  • Neutral or modest weight loss
  • Severe cachexia
  • Induces muscle hypertrophy

Correct Answer: Neutral or modest weight loss

Q16. Besides type 2 diabetes, metformin is commonly used off-label for which endocrine condition?

  • Hyperthyroidism
  • Polycystic ovary syndrome (PCOS)
  • Cushing’s syndrome
  • Addison’s disease

Correct Answer: Polycystic ovary syndrome (PCOS)

Q17. Which drug interaction can increase metformin plasma levels by reducing renal clearance?

  • Amoxicillin
  • Cimetidine
  • Vitamin C
  • Metoprolol

Correct Answer: Cimetidine

Q18. Which transporter on renal proximal tubule basolateral membrane facilitates cellular uptake of metformin from blood?

  • P-glycoprotein
  • OCT2 (organic cation transporter 2)
  • GLUT2
  • OATP1B3

Correct Answer: OCT2 (organic cation transporter 2)

Q19. An advantage of extended-release (ER) metformin formulations over immediate-release (IR) formulations is:

  • Increased hepatic metabolism
  • Higher peak plasma concentrations causing more GI upset
  • Reduced gastrointestinal adverse effects and once-daily dosing
  • Greater risk of lactic acidosis in all patients

Correct Answer: Reduced gastrointestinal adverse effects and once-daily dosing

Q20. Metformin’s effect on lipid profile is generally to:

  • Greatly increase LDL and triglycerides
  • Produce modest decreases in triglycerides and LDL
  • Eliminate HDL entirely
  • Have no effect on lipids ever

Correct Answer: Produce modest decreases in triglycerides and LDL

Q21. At the mitochondrial level, metformin inhibits which complex, contributing to decreased hepatic ATP production?

  • Complex IV (cytochrome c oxidase)
  • Complex I (NADH:ubiquinone oxidoreductase)
  • ATP synthase exclusively
  • Complex II (succinate dehydrogenase)

Correct Answer: Complex I (NADH:ubiquinone oxidoreductase)

Q22. Which laboratory parameter is most important to monitor regularly in patients taking metformin?

  • Serum amylase
  • Serum creatinine/eGFR
  • Thyroid stimulating hormone (TSH)
  • Serum potassium

Correct Answer: Serum creatinine/eGFR

Q23. In treatment guidelines, metformin is recommended as first-line therapy for:

  • Type 1 diabetes as monotherapy
  • Type 2 diabetes unless contraindicated
  • All patients with hypertension
  • Hyperthyroidism

Correct Answer: Type 2 diabetes unless contraindicated

Q24. Metformin’s glucose-lowering action is NOT due to which of the following?

  • Reduction of hepatic glucose output
  • Increased peripheral insulin sensitivity
  • Direct stimulation of insulin secretion from beta cells
  • Activation of AMPK signaling

Correct Answer: Direct stimulation of insulin secretion from beta cells

Q25. Is metformin absolutely contraindicated in pregnancy?

  • Yes, absolutely contraindicated in all pregnancies
  • No, it is sometimes used in gestational diabetes and PCOS during pregnancy
  • Only used topically in pregnancy
  • Used only after the first trimester

Correct Answer: No, it is sometimes used in gestational diabetes and PCOS during pregnancy

Q26. Metformin suppresses expression of key gluconeogenic enzymes. Which of the following enzymes is reduced?

  • Hexokinase
  • Phosphoenolpyruvate carboxykinase (PEPCK)
  • Pyruvate kinase
  • Acetyl-CoA carboxylase only

Correct Answer: Phosphoenolpyruvate carboxykinase (PEPCK)

Q27. Metformin increases the cellular AMP/ATP ratio primarily by:

  • Stimulating ATP synthase activity
  • Inhibiting mitochondrial respiratory chain complex I
  • Enhancing glycolysis rate only
  • Blocking ATP-dependent ion channels in beta cells

Correct Answer: Inhibiting mitochondrial respiratory chain complex I

Q28. Which clinical scenario increases the risk of metformin-associated lactic acidosis and warrants avoidance of metformin?

  • Well-controlled hypertension on ACE inhibitor
  • Acute myocardial infarction or cardiogenic shock
  • Mild osteoarthritis
  • Stable hypothyroidism on levothyroxine

Correct Answer: Acute myocardial infarction or cardiogenic shock

Q29. For patients on long-term metformin who develop unexplained neuropathy, which test should be considered?

  • Serum vitamin B12 level
  • Fasting cortisol
  • Anti-nuclear antibody titer
  • Serum calcium

Correct Answer: Serum vitamin B12 level

Q30. In cases of severe metformin overdose with lactic acidosis, the most appropriate life-saving intervention is:

  • Activated charcoal only
  • Immediate hemodialysis to remove metformin and correct acidosis
  • Administration of oral glucose
  • High-dose corticosteroids

Correct Answer: Immediate hemodialysis to remove metformin and correct acidosis

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