Hydantoins – Mephenytoin MCQs With Answer

Hydantoins – Mephenytoin MCQs With Answer

Hydantoins are a key anticonvulsant class important for B. Pharm students learning antiseizure pharmacology. This concise guide focuses on hydantoin chemistry, mechanism (voltage‑gated sodium channel blockade), pharmacokinetics, therapeutic uses, adverse effects and drug interactions, with special emphasis on mephenytoin’s clinical profile and safety concerns. Topics include enzyme induction, genetic variability in metabolism, monitoring parameters, and comparisons with phenytoin and other antiepileptics. The questions are designed to deepen understanding, reinforce clinical relevance and improve exam readiness for pharmacology, therapeutics and dosage regimen topics. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which chemical feature characterizes hydantoin anticonvulsants?

• A five‑membered imidazole ring
• A hydantoin (imidazolidine‑2,4‑dione) ring
• A benzodiazepine core
• A barbiturate pyrimidine ring

Correct Answer: A hydantoin (imidazolidine‑2,4‑dione) ring

Q2. What is the primary antiseizure mechanism of hydantoins like phenytoin and mephenytoin?

• Enhancement of GABA synthesis
• Inhibition of T‑type calcium channels
• Blockade and stabilization of voltage‑gated sodium channels
• Agonism at NMDA receptors

Correct Answer: Blockade and stabilization of voltage‑gated sodium channels

Q3. Mephenytoin is best described as which of the following?

• A first‑line drug for absence seizures
• An experimental benzodiazepine
• A hydantoin derivative with limited clinical use due to safety concerns
• An opioid analgesic

Correct Answer: A hydantoin derivative with limited clinical use due to safety concerns

Q4. Which adverse hematologic reaction is most historically associated with mephenytoin?

• Autoimmune hemolysis
• Agranulocytosis and severe blood dyscrasias
• Eosinophilia only
• Polycythemia vera

Correct Answer: Agranulocytosis and severe blood dyscrasias

Q5. Which hydantoin is known for zero‑order (saturation) kinetics at therapeutic concentrations?

• Ethosuximide
• Phenytoin
• Carbamazepine
• Valproate

Correct Answer: Phenytoin

Q6. Which monitoring tests are essential when a patient is receiving hydantoin therapy?

• Serum drug levels, liver function tests and complete blood count
• Only blood glucose levels
• EEG daily without any lab tests
• Urinalysis only

Correct Answer: Serum drug levels, liver function tests and complete blood count

Q7. Fetal hydantoin syndrome is associated with which of the following fetal effects?

• Neural tube defects exclusively
• Craniofacial abnormalities, growth deficiency and limb defects
• Only reversible neonatal jaundice
• No teratogenic risk

Correct Answer: Craniofacial abnormalities, growth deficiency and limb defects

Q8. Which adverse effect is classically linked to chronic phenytoin therapy?

• Gingival hyperplasia and hirsutism
• Hyperglycemia and weight gain only
• Tone deafness
• Hypothyroidism only

Correct Answer: Gingival hyperplasia and hirsutism

Q9. Which statement about hydantoin metabolism is most accurate?

• They are excreted unchanged in urine without hepatic metabolism
• They undergo hepatic metabolism and may be affected by genetic polymorphisms
• They are metabolized exclusively by renal tubular secretion
• They are metabolized solely by gut flora

Correct Answer: They undergo hepatic metabolism and may be affected by genetic polymorphisms

Q10. What is a common acute sign of phenytoin toxicity?

• Peripheral neuropathy without neurologic signs
• Nystagmus and ataxia
• Profound hyperreflexia only
• Isolated hypertension

Correct Answer: Nystagmus and ataxia

Q11. Which hydantoin is often used intravenously for status epilepticus (or its prodrug is used)?

• Mephenytoin IV is routine
• Fosphenytoin (prodrug of phenytoin)
• Ethotoin IV is standard
• Phenobarbital only, never phenytoin or fosphenytoin

Correct Answer: Fosphenytoin (prodrug of phenytoin)

Q12. How do hydantoins typically affect other drugs metabolized by the liver?

• They are strong CYP inhibitors and increase levels of other drugs
• They induce hepatic enzymes and may decrease plasma levels of coadministered drugs
• They have no effect on hepatic enzymes
• They only inhibit renal drug excretion

Correct Answer: They induce hepatic enzymes and may decrease plasma levels of coadministered drugs

Q13. Which contraceptive consideration is important when a woman is taking hydantoins?

• Hydantoins increase oral contraceptive levels causing toxicity
• Hydantoins induce metabolism of steroid contraceptives reducing their efficacy
• Hydantoins neutralize all hormones making contraception more effective
• No interaction with hormonal contraception

Correct Answer: Hydantoins induce metabolism of steroid contraceptives reducing their efficacy

Q14. Which seizure type is most likely to respond to hydantoin therapy?

• Typical absence seizures
• Generalized tonic‑clonic and complex partial seizures
• Infantile spasms only
• None — hydantoins are not anticonvulsants

Correct Answer: Generalized tonic‑clonic and complex partial seizures

Q15. Why was clinical use of mephenytoin limited or discontinued in many settings?

• Because it had no antiseizure activity
• Due to unpredictable severe hematologic toxicity and idiosyncratic reactions
• Because it caused permanent hearing loss in all patients
• Because it was too expensive compared with sugar pills

Correct Answer: Due to unpredictable severe hematologic toxicity and idiosyncratic reactions

Q16. Which laboratory abnormality may develop with chronic hydantoin therapy due to folate interference?

• Pancytopenia unrelated to folate
• Megaloblastic anemia due to folate deficiency
• Polycythemia secondary to increased erythropoietin
• Hypercalcemia only

Correct Answer: Megaloblastic anemia due to folate deficiency

Q17. In hypoalbuminemia, how should total measured phenytoin concentrations be interpreted?

• Total levels are unchanged and reflect free drug accurately
• Total phenytoin may be low while free (active) concentration is normal or elevated
• Total levels are always higher than free levels and need no correction
• Albumin has no effect on phenytoin binding

Correct Answer: Total phenytoin may be low while free (active) concentration is normal or elevated

Q18. Which adverse cutaneous reaction is a serious, though uncommon, risk with hydantoins?

• Contact dermatitis only
• Stevens‑Johnson syndrome and other severe rash
• Alopecia exclusively
• Vitiligo as the most common reaction

Correct Answer: Stevens‑Johnson syndrome and other severe rash

Q19. What pharmacokinetic property makes phenytoin dosing challenging?

• Linear first‑order kinetics over all doses
• Nonlinear kinetics leading to disproportionate concentration increases with small dose changes
• It is not absorbed orally
• It is exhaled unchanged via the lungs

Correct Answer: Nonlinear kinetics leading to disproportionate concentration increases with small dose changes

Q20. Which monitoring is particularly important soon after initiating or changing a hydantoin dosage?

• Serum drug concentration and clinical signs of toxicity
• Only an annual eye exam
• No monitoring is required
• Only measurement of urine specific gravity

Correct Answer: Serum drug concentration and clinical signs of toxicity

Q21. Which statement about hydantoin use in pregnancy is correct?

• Hydantoins are completely safe in pregnancy with no monitoring
• They carry teratogenic risk and require risk‑benefit assessment and monitoring
• They cure epilepsy permanently so pregnancy considerations are irrelevant
• They improve fetal development and are recommended for all pregnant women

Correct Answer: They carry teratogenic risk and require risk‑benefit assessment and monitoring

Q22. Which facility‑related precaution is important when administering IV phenytoin?

• Infuse rapidly as a bolus without monitoring
• Administer slowly and monitor cardiac rhythm because of arrhythmia risk
• Always dilute in pure water and inject into artery
• No special precautions are needed

Correct Answer: Administer slowly and monitor cardiac rhythm because of arrhythmia risk

Q23. Which drug is a prodrug formulated to avoid IV phenytoin’s solubility and cardiovascular issues?

• Fosphenytoin
• Levetiracetam
• Phenobarbital sodium
• Mephenytoin sulfate

Correct Answer: Fosphenytoin

Q24. Which of the following seizure types may be worsened by hydantoin therapy?

• Generalized tonic‑clonic seizures
• Absence seizures (may be ineffective or worsen them)
• Focal seizures with secondary generalization
• Febrile seizures in children under simple circumstances

Correct Answer: Absence seizures (may be ineffective or worsen them)

Q25. Which skeletal complication can result from long‑term hydantoin therapy?

• Osteomalacia and reduced bone density due to vitamin D metabolism induction
• Hyperostosis of the long bones exclusively
• Immediate fracture in all patients
• No effect on bone health

Correct Answer: Osteomalacia and reduced bone density due to vitamin D metabolism induction

Q26. Which patient factor increases the risk of hydantoin toxicity without dose change?

• Hypoalbuminemia
• High red blood cell count only
• Strong muscle hypertrophy
• Elevated platelet count only

Correct Answer: Hypoalbuminemia

Q27. Genetic polymorphism in drug‑metabolizing enzymes can affect which aspect of mephenytoin therapy?

• Only the taste of the tablet
• Metabolic rate and risk of accumulation or toxicity
• Its ability to cross the blood‑brain barrier in all individuals
• No clinical consequence at all

Correct Answer: Metabolic rate and risk of accumulation or toxicity

Q28. Which lab test should be done periodically because mephenytoin can cause unpredictable blood dyscrasias?

• Serum creatine kinase only
• Complete blood count with differential
• Fasting lipid profile only
• Urine pregnancy test only

Correct Answer: Complete blood count with differential

Q29. Which drug interaction is expected with hydantoins due to enzyme induction?

• Increased anticoagulant effect of warfarin
• Reduced plasma levels and effect of warfarin and oral contraceptives
• Complete antagonism of insulin action
• Hydantoins have no drug interactions

Correct Answer: Reduced plasma levels and effect of warfarin and oral contraceptives

Q30. For which of the following is therapeutic drug monitoring especially useful with hydantoin therapy?

• Assessing steady‑state levels and avoiding toxicity given narrow therapeutic index
• Measuring immediate antihypertensive effect
• Estimating renal tubular reabsorption rates
• Detecting viral infections

Correct Answer: Assessing steady‑state levels and avoiding toxicity given narrow therapeutic index

Q31. Which adverse neurological effect indicates toxicity and warrants dose reduction or monitoring?

• Improved cognition and alertness
• Dysarthria, ataxia and nystagmus
• Enhanced reflexes and increased muscle strength
• Clear improvement in school performance

Correct Answer: Dysarthria, ataxia and nystagmus

Q32. Which hydantoin is historically linked with a metabolite implicated in sedation and adverse effects?

• Mephenytoin (with metabolites associated with toxicity)
• Ibuprofen
• Paracetamol
• Metformin

Correct Answer: Mephenytoin (with metabolites associated with toxicity)

Q33. Which dosing consideration is important due to nonlinear kinetics of some hydantoins?

• Small dose increases may lead to disproportionately large increases in plasma concentration
• Dose can be doubled daily without consequence
• No need to adjust doses for age or comorbidity
• All doses result in identical plasma levels across patients

Correct Answer: Small dose increases may lead to disproportionately large increases in plasma concentration

Q34. Which symptomatic sign would prompt immediate discontinuation and hematologic workup in a patient on mephenytoin?

• New onset sore throat, fever and signs of infection
• Mild transient headache only
• Improved seizure control
• Temporary dry mouth after one dose

Correct Answer: New onset sore throat, fever and signs of infection

Q35. Which of the following is a pharmacologic advantage of fosphenytoin over phenytoin IV?

• It is less expensive
• Improved water solubility and lower risk of local cardiovascular toxicity
• It has identical adverse effect profile with no differences
• It cannot be converted to active phenytoin

Correct Answer: Improved water solubility and lower risk of local cardiovascular toxicity

Q36. Which counseling point is important when stopping hydantoin therapy?

• Stop abruptly to avoid side effects
• Taper gradually to reduce risk of seizure recurrence
• Double the dose for two days before stopping
• No special measures are needed

Correct Answer: Taper gradually to reduce risk of seizure recurrence

Q37. In which patient population should hydantoin dosing be approached with extra caution due to altered clearance?

• Young, healthy adults only
• Elderly patients and those with hepatic impairment
• Patients with strong muscle mass only
• Those who exercise frequently only

Correct Answer: Elderly patients and those with hepatic impairment

Q38. Which drug class interaction is most likely when a hydantoin induces CYP enzymes?

• Reduced efficacy of oral anticoagulants and hormonal contraceptives
• Increased therapeutic effect of benzodiazepines universally
• Complete protection from all infections
• Immediate cure of diabetes mellitus

Correct Answer: Reduced efficacy of oral anticoagulants and hormonal contraceptives

Q39. Which monitoring parameter helps interpret total phenytoin levels in hypoalbuminemic patients?

• Serum bilirubin level
• Serum albumin or free phenytoin concentration
• Serum creatinine kinase
• Serum chloride only

Correct Answer: Serum albumin or free phenytoin concentration

Q40. Which clinical use is least appropriate for hydantoins?

• Treatment of generalized tonic‑clonic seizures
• Acute management of status epilepticus with IV formulations
• First‑line therapy for typical absence seizures
• Second‑line therapy for partial seizures

Correct Answer: First‑line therapy for typical absence seizures

Q41. Which mechanism explains gingival hyperplasia with hydantoin therapy?

• Direct bacterial infection of gums
• Stimulation of gingival fibroblast proliferation and collagen synthesis
• Autoimmune destruction of gingival tissue
• Excessive tooth brushing only

Correct Answer: Stimulation of gingival fibroblast proliferation and collagen synthesis

Q42. Which adverse effect is particularly concerning for long‑term quality of life and requires supplementation or monitoring?

• Vitamin D induction leading to bone demineralization and need for bone health monitoring
• Improved bone density requiring no monitoring
• Permanent enhancement of vision requiring no treatment
• Chronic increase in appetite only

Correct Answer: Vitamin D induction leading to bone demineralization and need for bone health monitoring

Q43. When switching from phenytoin to another antiepileptic, which property of phenytoin complicates conversion?

• Its lack of oral formulations
• Nonlinear kinetics and enzyme induction causing variable interactions
• Its inability to cross the blood‑brain barrier
• Its instantaneous elimination from the body

Correct Answer: Nonlinear kinetics and enzyme induction causing variable interactions

Q44. Which sign would indicate serious cutaneous hypersensitivity to a hydantoin and require immediate discontinuation?

• Transient mild itch without systemic symptoms
• Widespread rash with mucosal involvement and systemic illness
• Minor localized redness at the application site only
• Temporary warmth at injection site only

Correct Answer: Widespread rash with mucosal involvement and systemic illness

Q45. Which statement about oral absorption of hydantoins is true?

• Hydantoins are completely insoluble and never absorbed
• Oral absorption is generally good but can be affected by formulation and drug interactions
• They are only effective when injected directly into the CSF
• Absorption occurs only after coadministration with fatty foods

Correct Answer: Oral absorption is generally good but can be affected by formulation and drug interactions

Q46. Which clinical laboratory abnormality should prompt suspicion of hydantoin‑induced bone marrow suppression?

• Marked leukopenia or agranulocytosis on CBC
• Isolated high HDL cholesterol
• Elevated serum sodium only
• Low urine specific gravity only

Correct Answer: Marked leukopenia or agranulocytosis on CBC

Q47. Which approach reduces the risk of neonatal complications when a pregnant woman must remain on hydantoin therapy?

• Abruptly stopping medication at conception
• Careful risk‑benefit assessment, folate supplementation and close monitoring
• Doubling the dose during pregnancy to prevent seizures
• No special measures are necessary

Correct Answer: Careful risk‑benefit assessment, folate supplementation and close monitoring

Q48. Which of the following hydantoins is least likely to be used clinically today because of safety and availability of better agents?

• Mephenytoin
• Phenytoin (widely used where appropriate)
• Fosphenytoin (used as prodrug in emergencies)
• Modern broad‑spectrum agents like levetiracetam

Correct Answer: Mephenytoin

Q49. Which pharmacodynamic effect explains why hydantoins reduce high‑frequency repetitive neuronal firing?

• Promotion of excitatory neurotransmitter release
• Stabilization of the inactivated state of sodium channels limiting repetitive firing
• Direct blockade of GABA receptors
• Activation of voltage‑gated calcium channels

Correct Answer: Stabilization of the inactivated state of sodium channels limiting repetitive firing

Q50. Which patient counseling point is important when starting any hydantoin therapy?

• Avoid monitoring and follow‑up unless problems occur
• Report signs of infection, rash, dizziness or gum changes and attend regular follow‑up for blood tests
• Stop the drug immediately at first missed dose
• Assume hydantoins have no interactions and take all other drugs as usual without consultation

Correct Answer: Report signs of infection, rash, dizziness or gum changes and attend regular follow‑up for blood tests

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