Succinimides – Phensuximide MCQs With Answer

Succinimides – Phensuximide MCQs With Answer

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Succinimides – Phensuximide MCQs With Answer

Succinimides are a key antiepileptic class used primarily for absence seizures; phensuximide is an important member studied in pharmacology and therapeutics. This concise, targeted introduction for B. Pharm students covers mechanism of action, pharmacokinetics, metabolism, adverse effects, drug interactions, monitoring parameters and therapeutic considerations of succinimides. Emphasis is on clinical application, rational dosing decisions, toxicity recognition and laboratory surveillance. The following set of 50 MCQs, with explanations of correct choices implicit in the options, is designed to reinforce drug knowledge, exam preparation and practical dispensing skills. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which seizure type is phensuximide primarily indicated for?

  • Generalized tonic-clonic seizures
  • Absence (petit mal) seizures
  • Myoclonic seizures
  • Focal seizures with secondary generalization

Correct Answer: Absence (petit mal) seizures

Q2. The main pharmacological mechanism of succinimide anticonvulsants like phensuximide is:

  • Enhancement of GABA-A receptor chloride conductance
  • Blockade of voltage-gated sodium channels
  • Inhibition of T-type calcium channels in thalamic neurons
  • Activation of NMDA receptors

Correct Answer: Inhibition of T-type calcium channels in thalamic neurons

Q3. Succinimide drugs are chemically classified as derivatives of which core structure?

  • Barbituric acid
  • Hydantoin
  • Succinimide ring
  • Benzodiazepine ring

Correct Answer: Succinimide ring

Q4. Which of the following is a common adverse effect associated with phensuximide?

  • Nephrolithiasis
  • Gastrointestinal upset and anorexia
  • Hyperthyroidism
  • Peripheral neuropathy

Correct Answer: Gastrointestinal upset and anorexia

Q5. Regarding protein binding and distribution, succinimides generally:

  • Are highly protein bound (>95%) and confined to plasma
  • Have low to moderate protein binding and penetrate the CNS
  • Do not cross the blood–brain barrier
  • Accumulate primarily in adipose tissue

Correct Answer: Have low to moderate protein binding and penetrate the CNS

Q6. Which organ system should be monitored because succinimides are extensively metabolized there?

  • Renal system only
  • Hepatic system
  • Cardiovascular system
  • Respiratory system

Correct Answer: Hepatic system

Q7. A serious but less common hematologic adverse effect of succinimides is:

  • Thrombocytopenia or agranulocytosis
  • Polycythemia
  • Eosinophilia with airway obstruction
  • Hemophilia

Correct Answer: Thrombocytopenia or agranulocytosis

Q8. Which laboratory test is most relevant before and during long-term phensuximide therapy?

  • Serum amylase
  • Complete blood count (CBC)
  • Fasting lipid profile
  • Serum magnesium

Correct Answer: Complete blood count (CBC)

Q9. Phensuximide is primarily eliminated from the body as:

  • Unchanged parent drug via feces
  • Active metabolites excreted in sweat
  • Hepatic metabolites excreted in urine
  • Exhaled unchanged through lungs

Correct Answer: Hepatic metabolites excreted in urine

Q10. Which drug interaction is most likely with succinimides due to hepatic metabolism?

  • Synergistic effect with ibuprofen through renal competition
  • Reduced clearance when co-administered with potent CYP inhibitors
  • Increased urinary excretion when given with loop diuretics
  • No clinically relevant interactions known

Correct Answer: Reduced clearance when co-administered with potent CYP inhibitors

Q11. In terms of teratogenic risk, succinimides like phensuximide should be:

  • Considered absolutely safe in pregnancy
  • Used with caution; risk-benefit assessment needed in pregnancy
  • Contraindicated because they cause congenital heart defects in all cases
  • Recommended to replace folic acid treatment

Correct Answer: Used with caution; risk-benefit assessment needed in pregnancy

Q12. Which monitoring is important due to possible hepatic enzyme induction or inhibition?

  • ECG monitoring weekly
  • Serum transaminases (LFTs)
  • Bone densitometry every month
  • Skin biopsy for rash

Correct Answer: Serum transaminases (LFTs)

Q13. Which succinimide is most commonly referenced in textbooks for absence seizure therapy?

  • Ethosuximide
  • Phenytoin
  • Carbamazepine
  • Diazepam

Correct Answer: Ethosuximide

Q14. The onset of action for oral succinimides is generally:

  • Immediate within minutes
  • Slow to moderate due to oral absorption and distribution
  • Only after IV administration
  • Dependent on inhalational route

Correct Answer: Slow to moderate due to oral absorption and distribution

Q15. A clinician should avoid prescribing succinimides with which class of drugs due to risk of increased CNS depression?

  • Benzodiazepines and other sedatives
  • Topical antibiotics
  • Inhaled bronchodilators
  • Thyroid hormone replacements

Correct Answer: Benzodiazepines and other sedatives

Q16. Which adverse effect can suggest overdose or toxicity with succinimides?

  • Hyperreflexia and agitation
  • Profound lethargy, ataxia and coma
  • Isolated hypertension without CNS signs
  • Pruritus limited to palms

Correct Answer: Profound lethargy, ataxia and coma

Q17. In the context of seizure pharmacotherapy, succinimides are classified primarily as:

  • Sodium channel blockers
  • GABA analogues
  • Calcium channel modulators (T-type)
  • Carbonic anhydrase inhibitors

Correct Answer: Calcium channel modulators (T-type)

Q18. Which population requires careful dose adjustment or avoidance of succinimides?

  • Patients with severe hepatic impairment
  • Healthy young adults with no comorbidities
  • Patients with well-controlled hypertension only
  • Individuals with seasonal allergies

Correct Answer: Patients with severe hepatic impairment

Q19. Which symptom is a common early central nervous system side effect of succinimides?

  • Insomnia and hyperactivity
  • Dizziness and somnolence
  • Increased visual acuity
  • Significant euphoria

Correct Answer: Dizziness and somnolence

Q20. For therapeutic drug monitoring of succinimides, which parameter is most useful clinically?

  • Serum drug concentration for some agents, plus clinical seizure control and side effects
  • Daily urine pH measurement
  • Monthly chest X-ray
  • Serum potassium levels

Correct Answer: Serum drug concentration for some agents, plus clinical seizure control and side effects

Q21. Which structural feature differentiates succinimide anticonvulsants from other classes?

  • A fused benzodiazepine core
  • A five-membered imide ring derived from succinic acid
  • A sulfonamide moiety
  • A barbiturate-like di-keto structure

Correct Answer: A five-membered imide ring derived from succinic acid

Q22. A pharmacist counseling a patient on phensuximide should advise that it may:

  • Cause increased appetite and weight gain only
  • Cause gastrointestinal upset, dizziness and advise to avoid driving until stable
  • Require refrigeration and protected light storage
  • Be taken only as needed for breakthrough seizures

Correct Answer: Cause gastrointestinal upset, dizziness and advise to avoid driving until stable

Q23. Which of the following drugs may worsen absence seizures and therefore is contraindicated with succinimides?

  • Ethosuximide
  • Carbamazepine
  • Methsuximide
  • Valproic acid

Correct Answer: Carbamazepine

Q24. The main site of action for T-type calcium channel blockade by succinimides is the:

  • Hippocampus
  • Thalamic relay neurons
  • Basal ganglia
  • Cerebellar Purkinje cells

Correct Answer: Thalamic relay neurons

Q25. In terms of drug metabolism, succinimides are most often subject to:

  • Renal secretion of unchanged drug without metabolism
  • Phase I hepatic oxidation followed by conjugation
  • Gut bacterial activation exclusively
  • Direct exhalation as volatile compounds

Correct Answer: Phase I hepatic oxidation followed by conjugation

Q26. Which adverse dermatologic reaction should prompt immediate discontinuation of phensuximide?

  • Mild dry skin
  • Severe rash or signs of Stevens–Johnson syndrome
  • Temporary hair loss after months
  • Localized acne at application site

Correct Answer: Severe rash or signs of Stevens–Johnson syndrome

Q27. When switching from another antiepileptic to a succinimide, the main clinical concern is:

  • Immediate risk of pulmonary edema
  • Seizure control during cross-titration and drug interactions
  • Loss of hearing due to vestibular toxicity
  • Hyperglycemia due to metabolic effects

Correct Answer: Seizure control during cross-titration and drug interactions

Q28. In pediatric patients, succinimides require dosing considerations because:

  • Children have slower hepatic metabolism than adults
  • Children may metabolize drugs differently, affecting dose and monitoring
  • They are ineffective in pediatric absence epilepsy
  • They are only given by IV in children

Correct Answer: Children may metabolize drugs differently, affecting dose and monitoring

Q29. Which pharmacokinetic property influences once versus multiple daily dosing of succinimides?

  • Drug pKa only
  • Plasma half-life and duration of action
  • Color of the tablet
  • Route of manufacturing

Correct Answer: Plasma half-life and duration of action

Q30. Which clinical feature distinguishes absence seizures that succinimides treat?

  • Prolonged convulsive tonic-clonic activity
  • Brief episodes of impaired awareness with staring and automatisms
  • Progressive focal motor weakness between attacks
  • Persistent postictal confusion lasting hours

Correct Answer: Brief episodes of impaired awareness with staring and automatisms

Q31. Which enzyme system is primarily implicated in metabolism of many anticonvulsants including succinimides?

  • CYP450 hepatic enzymes
  • Renal brush border enzymes
  • Plasma cholinesterases
  • Mitochondrial dehydrogenases in skeletal muscle

Correct Answer: CYP450 hepatic enzymes

Q32. Which formulation is the most common route of administration for phensuximide?

  • Oral tablets or syrup
  • Topical cream
  • Intramuscular depot injection
  • Transdermal patch

Correct Answer: Oral tablets or syrup

Q33. Combination therapy of succinimides with which agent requires careful monitoring for increased toxicity?

  • Acetaminophen
  • Valproic acid
  • Metformin
  • Vitamin C

Correct Answer: Valproic acid

Q34. Which adverse effect may require periodic ophthalmologic monitoring during prolonged succinimide therapy?

  • Optic neuritis or visual disturbances
  • Chronic conjunctivitis only
  • Retinal detachment in all patients
  • Increased intraocular pressure always

Correct Answer: Optic neuritis or visual disturbances

Q35. Which statement about tolerance and dependence with succinimides is correct?

  • They commonly produce physical dependence like benzodiazepines
  • Tolerance is not a major clinical issue; abrupt withdrawal may precipitate seizures
  • They always require daily escalation of dose to remain effective
  • They are used primarily as short-term anxiolytics due to dependence risk

Correct Answer: Tolerance is not a major clinical issue; abrupt withdrawal may precipitate seizures

Q36. During an overdose of succinimides, the initial management step is:

  • Induce hypothermia immediately
  • Supportive care with airway, breathing, circulation and activated charcoal if appropriate
  • Administer large doses of aspirin
  • Immediate hemodialysis in every case

Correct Answer: Supportive care with airway, breathing, circulation and activated charcoal if appropriate

Q37. Which pharmacodynamic interaction could reduce the effectiveness of succinimides?

  • Concurrent use of other T-type calcium channel blockers that have additive benefit
  • Co-administration of drugs that exacerbate absence seizures such as carbamazepine
  • Use with antacids that increase pH but have no CNS effects
  • Applying topical antibiotics concurrently

Correct Answer: Co-administration of drugs that exacerbate absence seizures such as carbamazepine

Q38. In terms of structure–activity relationship (SAR), modifications to the succinimide ring primarily affect:

  • Renal excretion only
  • Affinity for T-type channels and pharmacokinetic properties
  • Ability to bind to opioid receptors
  • Color and taste of oral tablets

Correct Answer: Affinity for T-type channels and pharmacokinetic properties

Q39. Which adverse metabolic effect is most likely with long-term anticonvulsant therapy, warranting periodic monitoring?

  • Hypocalcemia leading to bone demineralization
  • Acute pancreatitis in all patients
  • Severe hypernatremia routinely
  • Profound hypoglycemia

Correct Answer: Hypocalcemia leading to bone demineralization

Q40. Which counseling point is important regarding missed doses of phensuximide?

  • Double the next dose immediately to compensate
  • Take the missed dose as soon as remembered unless near the next dose; do not double doses
  • Stop therapy entirely if one dose is missed
  • Switch to an alternative drug without consulting prescriber

Correct Answer: Take the missed dose as soon as remembered unless near the next dose; do not double doses

Q41. Which adverse effect could indicate immune-mediated hypersensitivity to a succinimide?

  • Fever, rash and eosinophilia (DRESS-like picture)
  • Simple dry mouth without systemic features
  • Isolated transient headache of brief duration
  • Mild localized itching at injection site

Correct Answer: Fever, rash and eosinophilia (DRESS-like picture)

Q42. In drug development, why might medicinal chemists modify side chains on the succinimide core?

  • To increase tablet hardness only
  • To optimize CNS penetration, potency and metabolic stability
  • To ensure the drug tastes sweet
  • To convert it into an antibiotic

Correct Answer: To optimize CNS penetration, potency and metabolic stability

Q43. Which symptom in a pediatric patient on a succinimide would require urgent evaluation?

  • Mild transient sleepiness after dose
  • New onset frequent bruising or bleeding
  • Temporary mild cough unrelated to medication
  • Occasional hiccups

Correct Answer: New onset frequent bruising or bleeding

Q44. Which statement about phensuximide and its use in elderly patients is most appropriate?

  • Elderly patients require no special consideration
  • Start at lower doses and monitor for CNS depression and drug interactions
  • Always contraindicated in patients over 65
  • Administer only intramuscularly in elderly

Correct Answer: Start at lower doses and monitor for CNS depression and drug interactions

Q45. Which pharmacologic property helps succinimides specifically suppress absence seizures without strongly affecting other seizure types?

  • Selective blockade of high-voltage-activated L-type calcium channels
  • Preferential inhibition of low-threshold (T-type) calcium currents involved in thalamocortical rhythms
  • Strong antagonism at cholinergic receptors
  • Inhibition of glutamate uptake in peripheral nerves

Correct Answer: Preferential inhibition of low-threshold (T-type) calcium currents involved in thalamocortical rhythms

Q46. Which adverse effect is classically less associated with succinimides compared to older agents like phenobarbital?

  • Marked cognitive impairment and sedation
  • Any CNS effects
  • Mild GI upset
  • Rash in a subset of patients

Correct Answer: Marked cognitive impairment and sedation

Q47. Which is an important public health consideration when prescribing antiepileptics like phensuximide?

  • Ensuring adherence to avoid breakthrough seizures and injury
  • Ensuring patients stop as soon as they feel better
  • Promoting over-the-counter sharing of medication
  • Discouraging any communication with prescribers

Correct Answer: Ensuring adherence to avoid breakthrough seizures and injury

Q48. Which symptom would suggest a clinician to check serum levels or reassess therapy in a patient on phensuximide?

  • Improved seizure control without side effects
  • Increased frequency of absence spells or new neurologic symptoms
  • Occasional mild dry lips
  • Stable mood and functioning

Correct Answer: Increased frequency of absence spells or new neurologic symptoms

Q49. Which factor most affects oral bioavailability of succinimide drugs?

  • Stability in gastrointestinal tract and extent of first-pass hepatic metabolism
  • Ambient room temperature during administration
  • Patient’s eye color
  • Tablet imprinting design

Correct Answer: Stability in gastrointestinal tract and extent of first-pass hepatic metabolism

Q50. For exam preparation, which study approach best helps B. Pharm students master succinimide pharmacology?

  • Memorize brand names without understanding mechanisms
  • Integrate mechanism, clinical use, adverse effects, interactions and monitoring into clinical scenarios
  • Ignore adverse effects and focus only on chemistry
  • Rely solely on peer anecdotes for dosing guidance

Correct Answer: Integrate mechanism, clinical use, adverse effects, interactions and monitoring into clinical scenarios

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