Paper I
2013 April (2010 Scheme) · 40 marks · 180 min

Question

A 24year old man is brought to the hospital with complaints of unconsciousness , sustained contractions (toni

  • (a) What are the drugs that can be prescribed to this patient. 2 mark(s)
  • (b) Describe the pharmacokinetics and adverse effects of any one such drug. 3 mark(s)
  • (c) What is the treatment of status epilepticus. 1 mark(s)
Q16 marksEssays

Answer

(a) Drugs for status epilepticus

  • Diazepam (IV) or Lorazepam (IV) — first-line
  • Phenytoin / Fosphenytoin (IV) — second-line, for sustained control
  • Phenobarbitone (IV) — third-line
  • General anaesthesia (thiopentone/propofol) — refractory status epilepticus

(b) Pharmacokinetics and adverse effects of Phenytoin

  • Absorption: Oral absorption slow and variable; IV route used in emergencies (fosphenytoin preferred for IV/IM as it is water-soluble and less irritant)
  • Protein binding: ~90% bound to plasma proteins
  • Metabolism: Hepatic, by microsomal enzymes (CYP2C9/2C19); saturable (zero-order) kinetics at therapeutic doses — small dose increments can cause disproportionate rise in plasma levels
  • Enzyme induction: Potent inducer of hepatic microsomal enzymes — reduces efficacy of oral contraceptives, warfarin, corticosteroids
  • Excretion: Metabolites excreted in urine
  • Adverse effects:
    • Gum hypertrophy, hirsutism, coarsening of facial features
    • Cerebellar signs — nystagmus, ataxia, diplopia (dose-related)
    • Megaloblastic anaemia (folate deficiency)
    • Osteomalacia (vitamin D metabolism interference)
    • Hypersensitivity — rash, Stevens-Johnson syndrome
    • Fetal hydantoin syndrome (teratogenic)
    • Local: purple glove syndrome with IV extravasation

(c) Treatment of status epilepticus

  • Immediate: Maintain airway, breathing, circulation; check blood glucose (correct hypoglycaemia if present); IV access
  • First-line: IV Diazepam or Lorazepam (repeat once if seizures continue)
  • Second-line: IV Phenytoin/Fosphenytoin loading dose (if seizures persist)
  • Third-line: IV Phenobarbitone
  • Refractory status epilepticus: General anaesthesia with thiopentone/propofol/midazolam infusion, with EEG monitoring and ICU care

Other Years Asked


Revise MBBS
Preview