Phenytoin

Question 1

Mechanism of action of phenytoin

Answer 1

binds to sodium channels increasing their refractory period

Question 2

acute Adverse effects of phenytoin ?

Answer 2

dizziness,
diplopia,
nystagmus,
slurred speech,
ataxia

Question 3

Chronic Adverse effects of phenytoin ?

Answer 3

gingival hyperplasia
hirsutism,
coarsening of facial features,
drowsiness
megaloblastic anaemia (secondary to altered folate metabolism)
peripheral neuropathy
enhanced vitamin D metabolism causing osteomalacia
lymphadenopathy
dyskinesia

Question 4

Idiosyncratic effets

Answer 4

fever
rashes, including severe reactions such as toxic epidermal necrolysis
hepatitis
Dupuytren’s contracture*
aplastic anaemia
drug-induced lupus

Question 5

teratogenic effects ?

Answer 5

h cleft palate and congenital heart disease

Phenytoin induces vitamin K metabolism, which can cause a relative vitamin K deficiency, creating the potential for heamorrhagic disease of the newborn = scalp and skin bruising